Trane Video Game Controller CNT SVX07C EN User Manual

Installation and  
Operation  
Tracer ZN521  
Zone Controller  
CNT-SVX07C-EN  
 
Installation and  
Operation  
Tracer ZN521  
Zone Controller  
CNT-SVX07C-EN  
April 2005  
 
CNT-SVX07C-EN  
 
Tracer ZN521 Zone Controller Installation and Operation  
This guide and the information in it are the property of American Standard Inc. and may not be used or reproduced in whole or in part,  
without the written permission of American Standard Inc. Trane, a business of American Standard, Inc., has a policy of continuous  
product and product data improvement and reserves the right to change design and specification without notice.  
Although Trane has tested the hardware and software described in this guide, no guarantee is offered that the hardware and software  
are error free.  
Trane reserves the right to revise this publication at any time and to make changes to its content without obligation to notify any per-  
son of such revision or change.  
Trane may have patents or patent applications covering items in this publication. By providing this document, Trane does not imply  
giving license to these patents.  
The following are trademarks or registered trademarks of American Standard Inc.: Trane, Tracer, Rover.  
®
®
The following are trademarks or registered trademarks of their respective companies or organizations: BACnet from  
ASHRAE; Neuron, LonMark, LonTalk, and LonWorks from Echelon Corporation; National Electrical Code form the National  
Fire Proctection Association, Inc.  
Printed in the U.S.A.  
© 2005 American Standard Inc. All rights reserved  
CNT-SVX07C-EN  
 
NOTICE:  
Warnings and Cautions appear at appropriate sections throughout this manual. Read these carefully:  
ƽWARNING  
Indicates a potentially hazardous situation, which, if not avoided, could result in death or serious injury.  
ƽCAUTION  
Indicates a potentially hazardous situation, which, if not avoided, may result in minor or moderate injury.  
It may also be used to alert against unsafe practices.  
CAUTION  
Indicates a situation that may result in equipment damage or property damage.  
The following format and symbol conventions appear at appropriate sections throughout this manual:  
IMPORTANT  
Alerts installer, servicer, or operator to potential actions that could cause the product or system to  
operate improperly but will not likely result in potential for damage.  
Note:  
A note may be used to make the reader aware of useful information, to clarify a point, or to describe  
options or alternatives.  
This symbol precedes a procedure that consists of only a single step.  
CNT-SVX07C-EN  
 
 
Contents  
Chapter 4 Input/output functions and wiring for typical  
applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13  
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Contents  
ii  
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Contents  
Chapter 6 Status indicators for operation and  
communication. . . . . . . . . . . . . . . . . . . . . . . . . . . 51  
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iii  
 
Chapter 1  
Overview and specifications  
This guide provides installation and configuration information for the  
Tracer ZN521 zone controller, as well as a description of its operations.  
The overview includes a product description, specifications, and descrip-  
tions of ancillary products that may be necessary.  
Product description  
The Tracer ZN521 is an application-specific controller that provides  
direct-digital zone temperature control. The controller can operate as a  
stand-alone device or as part of a building automation system (BAS).  
Communication between the controller and a BAS occurs by means of a  
LonTalk communication link, which complies with the LonTalk protocol.  
The Tracer ZN521 supports the following equipment:  
Fan coils  
Unit ventilators  
Blower coils  
The Tracer ZN521 can be configured to control:  
Tri-state modulating or two-position valves  
Tri-state modulating dampers:  
outdoor/return air, and face-and-bypass  
DX cooling (single stage)  
Electric heat (two stages)  
It is designed to be field-installed and is sent from the factory unconfig-  
ured. Use the PC-based Rover service tool to configure the controller for  
specific applications  
Note:  
For information about using the Rover service tool, see the  
Rover Installation/Operation/Programming guide (EMTX-  
SVX01A-EN).  
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Chapter 1 Overview and specifications  
Storage environment  
If a Tracer ZN521 zone controller is to be stored for a substantial amount  
of time, store it in an indoor environment that meets the following  
requirements:  
Temperature: –40° to 185°F (–40° to 85°C)  
Relative humidity: 5–95%, noncondensing  
Dimensions  
Plastic-cover model dimensions  
For complete dimensional drawing, see Figure 1 on page 3.  
Height: 5.375 in. (137 mm)  
Width: 6.875 in. (175 mm)  
Depth: 2 in. (51 mm)  
Metal-cover model dimensions  
For complete dimensional drawing, see Figure 2 on page 3.  
Height: 9.0 in (25 mm)  
Width: 10.37in. (263 mm)  
Depth: 2.25 in. (58 mm)  
Clearances  
Plastic-cover model  
Front: 4.0 in. (102 mm)  
Each side: 1.0 in. (25 mm)  
Top and bottom: 4.0 in. (102 mm)  
Metal-cover model  
Front: 24.0 in. (610 mm)  
Each side: 2.0 in. (51 mm)  
Top and bottom: 1.0 in. (25 mm)  
2
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Clearances  
Figure 1. Plastic-cover model dimensions and clearances  
1 in  
(25 mm)  
4 in  
4 in.  
(102 mm)  
(102 mm)  
4 in  
(102 mm)  
5.625 in.  
(143 mm)  
6.875 in  
(175 mm)  
6.31  
(160 mm)  
5.625 in (143 mm)  
2 in. (51 mm)  
1 in  
(25 mm)  
Figure 2. Metal-cover model dimensions and clearances  
1 in.  
(25 mm)  
1.875 in.  
(48 mm)  
6.5 in.  
(165 mm)  
0.28 in.  
(7 mm)  
9 in.  
(229 mm)  
9 in.  
(229 mm)  
7 in.  
(178 mm)  
2 in.  
2 in.  
(51 mm)  
(51 mm)  
24 in.  
(610 mm)  
10.37 in.  
(263 mm)  
width with cover  
1 in.  
(25 mm)  
10.25 in.  
(260 mm)  
width without cover  
2.25in.  
(58 mm)  
Clearances  
Dimensions  
1 in.  
(25 mm)  
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Chapter 1 Overview and specifications  
Agency listing/compliance  
CE—Immunity: EN 50082-1:1997; EN 50082-2:1995  
CE—Emissions: EN 50081-1:1992 (CISPR 22) Class B  
UL and C-UL 916 listed: Energy management system  
UL 94-5V (UL flammability rating for plenum use)  
FCC Part 15, Class A  
ASHRAE Cycle 1 & Cycle 2 control sequences  
Additional components  
The Tracer ZN521 zone controller requires the use of additional compo-  
nents for monitoring and proper control of the associated equipment. The  
use of specific components depends on the application. These components  
are not included with the Tracer ZN521 zone controller.  
Power transformer  
Use a UL-listed Class 2 power transformer supplying a nominal 24 Vac  
(19–30 Vac) to power both the Tracer ZN521 zone controller (14 VA) and  
its associated output devices, including relays and actuators, to a maxi-  
mum of 12 VA per output utilized.  
Water, duct, and outdoor-air temperature sensors  
Temperature sensors must be Trane 10 k(at 25°C) thermistors. Enter-  
ing water and discharge air inputs may use a sealed temperature sensor  
(part number 4190 1100).  
Binary input switching devices  
Occupancy, condensate overflow, low-coil-temperature, and fan status  
inputs accept switching devices that may have normally open or normally  
closed dry contacts.  
Output devices  
Output devices connected to the Tracer ZN521 binary outputs cannot  
exceed 12 VA (0.5 A) current draw at 24 Vac.  
Zone temperature sensors  
Table 1 shows the Trane zone temperature sensors that are supported by  
the Tracer ZN521 zone controller.  
Valve actuators  
Valve actuators cannot exceed 12 VA draw at 24 Vac. For two-position  
valves, use actuators with on/off action, and with a spring action that  
4
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Additional components  
Table 1. Tracer zone temperature sensor options  
Timed  
override  
buttons  
Comm  
jack  
Fan  
Zone  
BAS  
order  
Use  
number  
Setpoint  
thumb-  
wheel  
Temperature  
High Med Low Auto  
Off  
On  
Cancel  
sensor  
4190 1087 Any  
4190 1088 Any  
4190 1090 Any  
4190 1094 Any  
4190 1095 Unit  
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
ventilator  
4190 1115  
4190 1116  
Fan coil  
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Unit  
ventilator  
4190 1117  
Any  
x
x
x
x
x
x
x
returns the valve to normally open or closed (dependent on the desired  
default position). For modulating valve control, use tri-state modulating  
actuators with or without a spring return, as required by the application.  
Damper actuators  
Damper actuators cannot exceed 12 VA draw at 24 Vac. For control of out-  
door/return air dampers, use tri-state modulating actuators that incorpo-  
rate a spring return.  
Zone humidity sensor  
For measurement of relative humidity (RH), the Tracer ZN521 requires a  
zone humidity sensor with a 4–20 mA output, where 4 mA is 0% RH and  
20 mA is 100% RH. The controller provides 20 Vdc to power the zone  
humidity sensor.  
CO2 sensor  
For CO2 measurement, the Tracer ZN521 requires a CO2 sensor with a 4–  
20 mA output, where 4 mA = 0 ppm and 20 mA = 2000 ppm.  
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Chapter 1 Overview and specifications  
6
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Chapter 2  
General wiring information  
This chapter provides specifications and general information about wir-  
ing the Tracer ZN521 zone controller. The controller requires wiring for:  
Input/output terminals  
AC power to the controller  
Communication-link wiring, if the controller is to communicate with a  
building automation system (BAS)  
Input/output terminal wiring  
All input/output terminal wiring for the Tracer ZN521 zone controller is  
application specific and dependant on the configuration of the controller.  
Input/output terminal wiring must meet the following requirements:  
All wiring must comply with the National Electrical Code and local  
codes.  
Use only 18 AWG, twisted-pair wire with stranded, tinned-copper  
conductors. (Shielded wire is recommended.)  
Binary input and output wiring must not exceed 1000 ft (300 m).  
Analog input wiring must not exceed 300 ft (100 m).  
Do not run input/output wires in the same wire bundle with any ac-  
power wires.  
For application-specific wiring information and diagrams, see Chapter 4,  
AC-power wiring  
ƽWARNING  
HAZARDOUS VOLTAGE!  
Before making line voltage electrical connections, lock open the supply-  
power disconnect switch. Failure to do so may cause death or serious  
injury.  
ƽCAUTION  
Make sure that the 24 Vac transformer is properly grounded. Failure to  
do so may result in damage to equipment and/or personal injury.  
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Chapter 2 General wiring information  
CAUTION  
Complete input/output wiring before applying power to the Tracer  
ZN521 zone controller. Failure to do so may cause damage to the con-  
troller or power transformer due to inadvertent connections to power  
circuits.  
IMPORTANT  
Do not share 24 Vac between controllers.  
All wiring must comply with National Electrical Code and local codes.  
The ac-power connections are in the top left corner of the Tracer ZN521  
zone controller (see Figure 3).  
Figure 3. Connecting ac-power wires to the controller  
H
24 Vac  
transformer  
N
The Tracer ZN521 may be powered by an existing transformer integral to  
the controlled equipment, provided the transformer has adequate power  
available and proper grounding is observed. If you are providing a new  
transformer for power, use a UL-listed Class 2 power transformer supply-  
ing a nominal 24 Vac (19–30 Vac). The transformer must be sized to pro-  
vide adequate power to both the Tracer ZN521 zone controller (14 VA)  
and its associated output devices, including relays and actuators, to a  
maximum of 12 VA per output utilized.  
8
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Communication-link wiring and addressing  
Communication-link wiring and  
addressing  
The Tracer ZN521 zone controller communicates with the BAS and with  
other LonTalk controllers by means of a LonTalk communication link.  
IMPORTANT  
For important instructions on network wiring, refer to the Tracer Sum-  
mit Hardware and Software Installation guide (BMTX-SVN01A-EN).  
Wiring for the communication link must meet the following require-  
ments:  
All wiring must comply with the National Electrical Code and local  
codes.  
22 AWG Level 4 unshielded communications wire recommended for  
most Comm5 installations.  
Termination resistors are required for wiring LonTalk devices com-  
municating on a network. For specific information about using termi-  
nation resistors for LonTalk applications, refer to the Tracer Summit  
Hardware and Software Installation guide (BMTX-SVN01A-EN).  
Each Tracer ZN521 zone controller has a unique 12-character alphanu-  
meric device address for communicating on a BAS network. This address,  
referred to as a Neuron ID, is assigned in the factory before the product is  
shipped and cannot be changed. Each controller can be identified by view-  
ing its unique Neuron ID, which is on a printed label attached to the cir-  
cuit board of the controller. Additional adhesive-backed, peel-off Neuron  
ID labels are tethered to the controller for placing on mechanical prints or  
unit location worksheets. The Neuron ID will appear when communica-  
tion is established with the Rover service tool or a BAS. An example Neu-  
ron ID is 00-01-64-1C-2B-00.  
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Chapter 2 General wiring information  
10  
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Chapter 3  
Mounting the controller  
This chapter gives recommendations and requirements for mounting a  
Tracer ZN521 zone controller.  
Location recommendations  
Trane recommends locating the Tracer ZN521 zone controller:  
Near the controlled piece of equipment to reduce wiring costs  
Where it is easily accessible for service personnel  
Where public access is restricted to minimize the possibility of tam-  
pering or vandalism  
The controller can often be mounted inside the wiring enclosure of the  
associated mechanical equipment.  
Operating environment requirements  
Operate a Tracer ZN521 zone controller in an indoor environment that  
meets the following requirements:  
Temperature: from 32°F to 140°F (from 0°C to 60°C)  
Relative humidity: 5–95%, noncondensing  
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Chapter 3 Mounting the controller  
Mounting recommendations  
Mounting recommendations are as follows:  
CAUTION  
Mount the Tracer ZN521 zone controller with the cover on to avoid the  
possibility of damaging the circuit board during installation.  
Mount the controller in any position, other than with the front of the  
cover facing downward.  
Mount using the two 3/16 in. (4.8 mm) radius mounting holes provided  
(see Figure 4). Mounting fasteners are not included.  
Attach the controller securely so it can withstand vibrations of associ-  
ated HVAC equipment.  
When the controller is mounted in a small enclosed compartment,  
complete all wiring connections before securing the controller in the  
compartment.  
Figure 4. Mounting the Tracer ZN521 zone controller  
12  
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Chapter 4  
Input/output functions and  
wiring for typical applications  
This chapter provides information about the function of inputs and out-  
puts and examples of wiring for typical applications. Applications sup-  
ported by the Tracer ZN521 zone controller are shown in Table 2.  
Table 2. Typical applications for the Tracer ZN521 zone controller  
Application  
2-pipe hydronic cooling only  
2-pipe hydronic heating only  
2-pipe changeover  
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
2-pipe steam only  
4-pipe hydronic heating and cooling  
4-pipe changeover  
x
x
4-pipe steam/chilled water  
Electric heat only (single- and two-stage)  
DX/hydronic heating  
×
x
x
x
x
x
x
x
DX/steam heating  
DX cooling only  
Figures 7 through 17 (pages 23 through 33) show typical wiring diagrams  
that include all required and all optional components for typical applica-  
tions.  
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13  
 
             
Chapter 4 Input/output functions and wiring for typical applications  
Binary inputs  
The Tracer ZN521 controller includes four binary inputs. Each binary  
input associates an input signal of 0 Vac with open contacts and 24 Vac  
with closed contacts. You can use the Rover service tool to configure each  
of the inputs as normally open or normally closed. If an application does  
not warrant the use of a particular input, configure the input as Not  
Used. This will disable the generation of diagnostics for this function.  
Table 3 gives the function of each binary input.  
Table 3. Binary inputs  
Binary input  
Function  
terminal label  
BI1  
BI2  
BI3  
BI4  
Low-coil-temperature detection  
Condensate overflow  
Occupancy or generic binary input  
Fan status  
Each function is explained in the following paragraphs. For an explana-  
tion of the diagnostics generated by each binary input, see “Diagnostics”  
on page 58. For more information about how the controller operates, see  
BI1: Low-coil-temperature detection  
Note:  
BI1 applies to hydronic/steam coils only.  
The function of low-coil-temperature detection is to protect the coil from  
freezing. If BI1 is wired to a binary low-coil-temperature detection device  
(freeze-protection switch) and a low-coil-temperature condition exists, the  
Tracer ZN521 will detect the condition and generate a Low Coil Temp  
Detection diagnostic.  
BI2: Condensate overflow  
The function of condensate overflow is to prevent the condensate drain  
pan from overflowing and causing water damage to the building. If BI2 is  
wired to a condensate overflow switch and the level of condensate reaches  
the trip point, the Tracer ZN521 will detect the condition and generate a  
Condensate Overflow diagnostic.  
14  
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Binary inputs  
BI3: Occupancy or generic binary input  
The BI3 binary input can function as either:  
The occupancy input  
A generic binary input  
The function of occupancy is to save energy by spreading zone setpoints  
when the zone is unoccupied. As the occupancy input, BI3 can be used for  
two related functions. For stand-alone controllers, BI3 can be hard-wired  
to a binary switch or timeclock to determine the occupancy mode—either  
occupied or unoccupied. For controllers receiving a BAS-communicated  
occupancy request, the function of BI3 is to change the mode from occu-  
pied to occupied standby. (For more information on occupancy-related  
BI3 is the only binary input that can be configured as generic. If config-  
ured as a generic binary input, it can be monitored by a BAS and has no  
direct effect on Tracer ZN521 operation.  
BI4: Fan status  
The fan status input provides feedback to the controller regarding the  
fan’s operating status. If BI4 is wired to a fan status switch and the input  
indicates that the fan is not operating when the controller has the fan  
controlled to on, the controller will generate a Low AirFlow—Fan Failure  
diagnostic. (For more information, see “Fan status” on page 49.)  
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Chapter 4 Input/output functions and wiring for typical applications  
Analog inputs  
The Tracer ZN521 controller includes seven analog inputs. Table 4  
describes their functions. Each function is explained in the following  
paragraphs. For an explanation of the diagnostics generated by each ana-  
log input, see “Diagnostics” on page 58. For more information about how  
Table 4. Analog inputs  
Analog input  
Function  
terminal label  
ZN  
GND  
SET  
FAN  
GND  
AI1  
Zone temperature  
Zone sensor common ground  
Local setpoint  
Fan mode input  
Auxiliary ground  
Entering water temperature  
Discharge air temperature  
Outdoor air temperature or generic temperature  
Universal 4–20 mA  
AI2  
AI3  
AI4  
GND: Ground terminals  
Use a GND terminal as the common ground for all zone sensor analog  
inputs.  
ZN: Zone temperature  
The ZN analog input functions as the local (hard-wired) zone temperature  
input. The controller receives the temperature as a resistance signal from  
a 10 kthermistor in a standard Trane zone sensor wired to analog input  
ZN. A zone temperature value communicated by means of a LonTalk link  
can also be used for controllers operating on a BAS. When both a hard-  
wired and communicated zone temperature value is present, the control-  
ler uses the communicated value. If neither a hard-wired nor a communi-  
cated zone temperature value is present, the controller generates a Zone  
Temp Failure diagnostic.  
The ZN analog input is also used to communicate timed override requests  
and cancel requests to the controller for applications using a Trane zone  
sensor with ON and CANCEL buttons.  
16  
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Analog inputs  
SET: Local setpoint  
The SET analog input functions as the local (hard-wired) temperature  
setpoint input for applications utilizing a Trane zone sensor with a tem-  
perature setpoint thumbwheel. The local setpoint input is configurable  
(as enabled or disabled) using the Rover service tool. A setpoint value  
communicated by means of a LonTalk link can also be used for controllers  
operating on a BAS. If both hard-wired and communicated setpoint val-  
ues are present, the controller uses the communicated value. If neither a  
hard-wired nor a communicated setpoint value is present, the controller  
uses the stored default setpoints (configurable using the Rover service  
tool). If a valid hard-wired or communicated setpoint value is established  
and then is no longer present, the controller generates a Setpoint Failure  
diagnostic.  
FAN: Fan mode input  
The FAN analog input functions as the local (hard-wired) fan mode  
switch input for applications using the Trane zone sensor with a fan mode  
switch option. The various fan mode switch positions (off, low, medium,  
high, auto) provide different resistances that are interpreted by the  
Tracer ZN521. The local fan mode switch input is configurable (as  
enabled or disabled) using the Rover service tool. A communicated fan  
mode request via the LonTalk communications link can also be used for  
controllers operating on a BAS. If both hard-wired and communicated fan  
mode values are present, the controller uses the communicated value. If  
neither a hard-wired nor a communicated fan mode value is present, the  
controller recognizes the fan mode value as auto and operates according  
to the default configuration. If a valid hard-wired or communicated fan  
mode value is established and then is no longer present, the controller  
generates a Fan Mode Failure diagnostic.  
AI1: Entering water temperature  
The AI1 analog input functions as the local (hard-wired) entering water  
temperature input. An entering water temperature communicated via the  
LonTalk communications link can also be used for controllers operating  
on a BAS. If both hard-wired and communicated entering water tempera-  
ture values are present, the controller uses the communicated value. If a  
valid hard-wired or communicated entering water temperature value is  
established and then is no longer present, the controller generates an  
Entering Water Temp Failure diagnostic.  
For units configured as 2-pipe or 4-pipe changeover units, the entering  
water temperature is used to make heating/cooling operation decisions. If  
neither a hard-wired nor a communicated entering water temperature  
value is present on changeover units, the controller will always operate in  
heating mode.  
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Chapter 4 Input/output functions and wiring for typical applications  
For units not configured as changeover units, the entering water temper-  
ature value is used for information and troubleshooting only and does not  
affect the operation of the controller.  
Note:  
AI1 is not polarity sensitive; you can connect either terminal to  
either sensor lead.  
AI2: Discharge air temperature  
The AI2 analog input functions as the local discharge air temperature  
input.  
IMPORTANT  
The Tracer ZN521 cannot operate without a valid discharge air tempera-  
ture value.  
The controller receives the temperature as a resistance signal from a  
10 kthermistor wired to analog input AI2. The thermistor is typically  
located downstream from all unit heating and cooling coils at the unit dis-  
charge area.  
If a discharge air temperature value is invalid or is not present, the con-  
troller generates a Discharge Air Temp Failure diagnostic and shuts  
down the equipment. When the thermistor returns to a valid tempera-  
ture, the controller automatically allows the equipment to resume normal  
operation.  
Note:  
AI2 is not polarity sensitive; you can connect either terminal to  
either sensor lead.  
AI3: Outdoor air temperature or generic temperature  
The AI3 analog input can function as either:  
An outdoor air temperature input  
A generic temperature input  
If AI3 is configured as the local (hard-wired) outdoor air temperature  
input, the controller receives the temperature as a resistance signal from  
a 10 kthermistor wired to analog input AI3. An outdoor air tempera-  
ture value communicated by means of a LonTalk link can also be used for  
controllers operating on a BAS. If both hard-wired and communicated  
outdoor air temperature values are present, the controller uses the com-  
municated value. If a valid hard-wired or communicated outdoor air tem-  
perature value is established and then is no longer present, the controller  
generates an Outdoor Air Temp Failure diagnostic.  
18  
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Analog inputs  
Economizing (free cooling) is a function whereby outdoor air is used as a  
source of cooling before hydronic or DX cooling is used. The Tracer ZN521  
uses the outdoor air temperature value to determine whether economiz-  
ing is feasible. Economizing is not possible without a valid outdoor air  
temperature. (For more information, see “Economizing (free cooling)” on  
page 45.)  
The outdoor air temperature value is also used for the freeze avoidance  
function. This function is used for low-coil-temperature protection when  
the fan is off. The controller enters the freeze avoidance mode when the  
outdoor air temperature is below the freeze avoidance setpoint (config-  
urable using the Rover service tool). (For more information, see “Freeze  
If AI3 is configured as a generic temperature input, it can be monitored  
by a BAS. The controller receives the temperature as a resistance signal  
from a 10 kthermistor wired to analog input AI3. The generic tempera-  
ture input can be used with any Trane 10 kthermistor. The thermistor  
can be placed in any location and has no effect on the operation of the con-  
troller. The controller will generate a Generic Temperature Failure diag-  
nostic if the input becomes invalid or goes out of range.  
Note:  
AI3 is not polarity sensitive; you can connect either terminal to  
either sensor lead.  
AI4: Universal 4–20 mA  
The AI4 analog input can be configured in one of the three ways shown in  
Table 5. AI4 configuration options and associated measurement ranges  
Configuration  
Measurement range  
Generic 4–20 mA input  
0–100%  
(4 mA=0%; 20 mA=100%)  
CO measurement  
0–2000 ppm  
2
(4 mA=0 ppm; 20 mA=2000 ppm)  
Relative humidity (RH) measurement 0–100%  
(4 mA=0% RH; 20 mA=100% RH)  
If this input is not needed for an application, configure it as Not Used.  
This will disable the generation of diagnostics.  
Note:  
AI4 is polarity sensitive.  
For the generic input configuration, a 4–20 mA sensor must be hard-  
wired to the AI4 terminal. (Wiring is dependent on the specific applica-  
tion.) The sensor communicates a value of 0–100% to the BAS. This con-  
figuration has no direct effect on Tracer ZN521 operation. If a valid value  
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19  
 
               
Chapter 4 Input/output functions and wiring for typical applications  
is established and then is no longer present, the controller generates a  
Generic AIP Failure diagnostic.  
For the CO2 measurement configuration, a 4–20 mA sensor must be hard-  
wired to the AI4 terminal as shown in Figure 5. The sensor will transmit  
a 0–2000 ppm value to the BAS. This configuration has no direct effect on  
Tracer ZN521 operation. If a valid value is established and then is no  
longer present, the controller generates a CO2 Sensor Failure diagnostic.  
Figure 5. AI4 terminal wiring: CO2 measurement  
Tracer ZN521  
24 Vac  
CO sensor  
2
(Trane 5010 0828 shown)  
24 Vac  
GND  
Signal  
For the RH measurement configuration, either a hard-wired 4–20 mA  
zone humidity sensor (see Figure 6) must provide a value to the controller  
or a BAS communicates a value to the controller. The controller uses this  
value to support the dehumidification function. (For more information,  
see “Dehumidification” on page 47.) If a valid hard-wired or communi-  
cated relative humidity value is established and then is no longer  
present, the controller generates a Humidity Input Failure diagnostic and  
disables the dehumidification function.  
Figure 6. AI4 terminal wiring: RH measurement  
Tracer ZN521  
RH sensor  
20  
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Binary outputs  
Binary outputs  
The ZN521 zone controller supports fan coil, blower coil, and unit ventila-  
tor applications that may include the following components:  
Supply fan with up to three speeds  
Hydronic cooling and/or heating coils with two-position or tri-state  
modulating control valve  
DX cooling (single stage)  
Electric heat (single stage or two stage)  
Baseboard heat (single stage)  
Tri-state modulating outdoor/return air damper  
Tri-state modulating face-and-bypass damper  
The Tracer ZN521 controller includes ten binary outputs. Each binary  
output is a triac with a rating of 12 VA at 24 Vac. Table 6 describes the  
function of each output.  
Table 6: Binary output functions  
Binary output  
Functions  
1
2
• Fan high  
• Fan medium  
• Exhaust fan or damper  
3
4
• Fan low  
• Modulating cooling/changeover valve, open  
• Two-position cooling/changeover valve  
• DX cooling  
5
6
• Modulating cooling/changeover valve, close  
• Face-and-bypass damper, open to face  
• Modulating heating valve, open  
• Two-position heating valve  
• Electric heat, stage 1  
7
• Modulating heating valve, close  
• Face-and-bypass damper, close (bypass)  
• Electric heat, stage 2  
8
9
• Outdoor air damper, open (return air damper, close)  
• Outdoor air damper, close (return air damper, open)  
10  
• Baseboard heat  
• Generic  
Generic binary output  
Binary output 10 is the only output that can be configured as a generic  
binary output. When configured as a generic binary output, it can be con-  
trolled only by a BAS, and has no direct effect on Tracer ZN521 operation.  
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21  
 
               
Chapter 4 Input/output functions and wiring for typical applications  
Overriding binary outputs  
The Tracer ZN521 controller includes a manual output test and a water  
valve override feature. Use the manual output test to manually control  
the outputs in a defined sequence. For information, see “Manual output  
The water valve override feature is a procedure used for water balancing.  
Using the Rover service tool or a BAS, a user can specify that a Tracer  
ZN521 override the state of water valves to:  
Open all valves  
Close all valves  
The controller resets itself to normal operation after two hours.  
Wiring requirements and options  
Table 7 shows required controller inputs for minimal proper operation of  
all applications.  
Table 7. Required controller inputs for proper operation  
For more information,  
Function  
24 Vac power  
Input source  
see:  
Terminals: GND, 24 V AC-power wiring” on  
Zone temperature  
Terminals: ZN, GND  
or communicated  
Discharge air temperature  
Terminals: AI2  
Entering water tempera-  
ture—required only for  
units with auto  
Terminal: AI1  
or communicated  
AI1: Entering water  
changeover  
Outdoor air temperature— Terminals: AI3 or  
AI3: Outdoor air tem-  
temperature” on  
required only for econo-  
mizing  
communicated  
Relative humidity—  
required only for dehu-  
midification  
Terminals: AI4  
Figure 7 on page 23 through Figure 17 on page 33 show typical applica-  
tions that include all required and all optional components.  
22  
CNT-SVX07C-EN  
 
             
Wiring requirements and options  
Figure 7. Two-pipe hydronic-cooling unit  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
24 V†  
Cooling valve  
24 V†  
Electric heat, stage 1 (optional)  
24 V†  
Electric heat, stage 2 (optional)  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
on page 20 for  
wiring options  
out  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
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23  
 
   
Chapter 4 Input/output functions and wiring for typical applications  
Figure 8. Two-pipe hydronic-heating unit  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
24 V†  
Occupancy (open=occupied)*  
Heating valve  
Condensate overflow (closed=normal)*  
24 V†  
Outdoor air damper actuator  
Low-coil-temperature detection  
(closed=normal)*  
24 V†  
H
N
Generic/baseboard heat  
24 Vac  
LonTalk  
in  
AI4 input: See  
wiring options  
out  
Outdoor air or generic temperature  
Entering water  
temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) termi-  
24  
CNT-SVX07C-EN  
 
 
Wiring requirements and options  
Figure 9. Two-pipe hydronic heating/cooling unit with auto changeover  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
24 V†  
Heating/cooling changeover valve  
24 V†  
Electric heat, stage 1 (optional)  
24 V†  
Electric heat, stage 2 (optional)  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
wiring options  
out  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
CNT-SVX07C-EN  
25  
 
 
Chapter 4 Input/output functions and wiring for typical applications  
Figure 10. Four-pipe hydronic heating/cooling unit  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
24 V†  
Cooling valve  
24 V†  
Heating valve  
Condensate overflow (closed=normal)*  
24 V†  
Low-coil-temperature detection  
(open=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
LonTalk  
in  
AI4 input: See  
wiring options  
out  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
26  
CNT-SVX07C-EN  
 
 
Wiring requirements and options  
Figure 11. Four-pipe heating/cooling unit with auto changeover  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
24 V†  
Occupancy (open=occupied)*  
Heating/cooling changeover valve  
24 V†  
Auxiliary heating valve  
Condensate overflow (closed=normal)*  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
LonTalk  
in  
AI4 input: See  
on page 20 for  
wiring options  
out  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
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27  
 
 
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
24 V†  
DX cooling  
24 V†  
Heating valve  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
1
2
3
4
5
6
7
8
9
10 STATUS  
LED  
BINARY OUTPUTS  
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
on page 20 for  
wiring options  
1
2
3
out  
On  
4
5
6
Cancel  
Outdoor air or generic temperature  
Entering water  
temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
 
 
24 V†  
Fan, high speed  
24 V†  
Exhaust  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
24 V†  
DX cooling  
24 V†  
Electric heat, stage 1 (optional)  
24 V†  
Electric heat, stage 2 (optional)  
24 V†  
Low-coil-temperaturedetection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
1
2
3
4
5
6
7
8
9
10 STATUS  
LED  
BINARY OUTPUTS  
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
on page 20 for  
wiring options  
1
2
3
out  
On  
4
5
6
Cancel  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
 
 
Chapter 4 Input/output functions and wiring for typical applications  
Figure 14. Electric heat unit  
24 V†  
Fan, high speed  
24 V†  
Exhaust  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
24 V†  
Electric heat, stage 1  
24 V†  
Condensate overflow (closed=normal)*  
Electric heat, stage 2  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
N
24 Vac  
Generic/baseboard heat  
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
on page 20 for  
wiring options  
out  
Outdoor air or  
generic temperature  
Entering water  
temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
30  
CNT-SVX07C-EN  
 
 
Wiring requirements and options  
Figure 15. Two-pipe heating unit with face-and-bypass damper  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
24 V†  
Face & bypass damper actuator  
24 V†  
Heat isolation valve, open/close  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
N
24 Vac  
Generic/baseboard heat  
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
wiring options  
out  
Outdoor air or  
generic temperature  
Entering water  
temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
CNT-SVX07C-EN  
31  
 
Chapter 4 Input/output functions and wiring for typical applications  
Figure 16. Two-pipe heating/cooling unit with face-and-bypass damper  
24 V†  
Fan, high speed  
24 V†  
Exhaust (or fan, medium speed)  
24 V†  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Condensate overflow (closed=normal)*  
Fan, low speed  
24 V†  
Heating/cooling isolation valve, open/close  
24 V†  
Face-and-bypass damper actuator  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
N
24 Vac  
Generic/baseboard heat  
LonTalk  
in  
AI4 input: See  
wiring options  
out  
Outdoor air or  
generic temperature  
Entering water  
temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
32  
CNT-SVX07C-EN  
 
 
Wiring requirements and options  
Figure 17. Four-pipe heating/cooling unit with face-and-bypass damper  
24 V†  
24 V†  
Fan, high speed  
Exhaust (or fan, medium speed)  
24 V†  
Fan, low speed  
24 V†  
Fan status (closed=on)*  
Occupancy (open=occupied)*  
Cooling isolation valve, open/close  
24 V†  
Face and bypass damper actuator  
Condensate overflow (closed=normal)*  
24 V†  
Heating isolation valve, open/close  
24 V†  
Low-coil-temperature detection  
(closed=normal)*  
Outdoor air damper actuator  
24 V†  
H
24 Vac  
Generic/baseboard heat  
N
LonTalk  
in  
AI4 input: See  
Figures 5 and 6  
on page 20 for  
wiring options  
out  
Entering water  
temperature  
Outdoor air or  
generic temperature  
LonTalk  
Discharge air  
temperature  
* All binary inputs are configurable.  
Connect 24 V to an AC POWER (24V) terminal.  
CNT-SVX07C-EN  
33  
 
   
Chapter 4 Input/output functions and wiring for typical applications  
34  
CNT-SVX07C-EN  
 
   
Chapter 5  
Sequence of operations  
The Tracer ZN521 zone controller will operate to maintain the zone tem-  
perature setpoint. This chapter discusses many of the operational  
sequences used by the controller to accomplish this goal.  
Power-up sequence  
When 24 Vac power is initially applied to the Tracer ZN521 zone control-  
ler, the following sequence occurs:  
1. The green status indicator LED turns on (see “Interpreting LEDs” on  
page 56).  
2. All outputs are controlled off. All modulating valves and dampers  
close, and the face-and-bypass damper calibrates to bypass (when  
present).  
3. The controller reads all input local values to determine initial values.  
4. The random-start timer begins (see “Random start” on page 35).  
5. If a hard-wired zone-temperature value is not detected, the controller  
begins to wait for a communicated value. (This can take several min-  
utes [15-minute default] and occurs concurrently with the remainder  
of the power-up sequence.)  
6. The random-start timer expires.  
7. The power-up control wait function begins automatically if the config-  
ured power-up control wait time is greater than 0 seconds. When this  
function is enabled, the controller waits for the configured amount of  
time (from 0 to 120 seconds) to allow a communicated occupancy  
request to arrive. If a communicated occupancy request arrives, nor-  
mal operation can begin. If a communicated occupancy request does  
not arrive, the controller assumes stand-alone operation.  
8. Normal operation begins assuming no diagnostics have been  
generated.  
Random start  
Random start is intended to prevent all units in a building from energiz-  
ing at the same time. The random-start timer delays the fan and any  
heating or cooling start-up from 5 to 30 seconds. If neither heating nor  
cooling is initiated, or if fan operation is not required during the delay, the  
random-start timer will time-out.  
CNT-SVX07C-EN  
35  
 
               
Chapter 5 Sequence of operations  
Occupancy modes  
Occupancy modes can be controlled by any of the following:  
The state of the local (hard-wired) occupancy binary input BI3 (see  
A timed override request from a Trane zone sensor (see “Timed over-  
A communicated signal from a peer device (see “Peer-to-peer commu-  
A communicated signal from a BAS  
A communicated request, either from a BAS or a peer controller, takes  
precedence over local requests. If a communicated occupancy request has  
been established and is no longer present, the controller reverts to the  
default (occupied) occupancy mode after 15 minutes (if no hard-wired  
occupancy request exists). The Tracer ZN521 has the following occupancy  
mode options:  
Occupied  
Unoccupied  
Occupied standby  
Occupied bypass  
Occupied mode  
In occupied mode, the controller maintains the zone temperature based  
on the occupied heating or cooling setpoints. The controller uses the occu-  
pied mode as a default mode when other forms of occupancy request are  
not present. The fan will run as configured (continuous or cycling). The  
outdoor air damper will close when the fan is off. The temperature set-  
points can be local (hard-wired), communicated, or stored default values  
(configurable using the Rover service tool).  
Unoccupied mode  
In unoccupied mode, the controller attempts to maintain the zone temper-  
ature based on the unoccupied heating or cooling setpoint. The fan will  
cycle between high speed and off. The outdoor air damper will remain  
closed, unless economizing. The controller always uses the stored default  
setpoint values (configurable using the Rover service tool), regardless of  
the presence of a hard-wired or communicated setpoint value.  
Occupied standby mode  
The controller is placed in occupied standby mode only when a communi-  
cated occupied request is combined with an unoccupied request from  
occupancy binary input BI3. In occupied standby mode, the controller  
maintains the zone temperature based on the occupied standby heating  
or cooling setpoints. Because the occupied standby setpoints are typically  
spread 2°F (1.1°C) in either direction and the outdoor air damper is  
closed, this mode reduces the demand for heating and cooling the space.  
36  
CNT-SVX07C-EN  
 
                 
Timed override control  
The fan will run as configured (continuous or cycling) for occupied mode.  
The controller always uses the stored default setpoint values (config-  
urable using the Rover service tool), regardless of hard-wired or commu-  
nicated setpoint values. In addition, the outdoor air damper uses the  
Economizer Occupied Standby Minimum Position setpoint to reduce the  
ventilation rate.  
Occupied bypass mode  
The controller is placed in occupied bypass mode when the controller is  
operating in the unoccupied mode and either the timed override ON but-  
ton on the Trane zone sensor is pressed or the controller receives a com-  
municated occupied bypass signal from a BAS. In occupied bypass mode,  
the controller maintains the zone temperature based on the occupied  
heating or cooling setpoints. The fan will run as configured (continuous or  
cycling). The outdoor air damper will close when the fan is off. The con-  
troller will remain in occupied bypass mode until either the CANCEL but-  
ton is pressed on the Trane zone sensor or the occupied bypass time  
(configurable using the Rover service tool) expires. The temperature set-  
points can be local (hard-wired), communicated, or stored default values  
(also configurable using the Rover service tool).  
Timed override control  
If the zone sensor has a timed override option (ON/CANCEL buttons), push-  
ing the ON button initiates a timed override on request. A timed override  
on request changes the occupancy mode from unoccupied mode to occu-  
pied bypass mode. In occupied bypass mode, the controller controls the  
zone temperature based on the occupied heating or cooling setpoints. The  
occupied bypass time, which resides in the Tracer ZN521 and defines the  
duration of the override, is configurable from 0 to 240 minutes (default  
value of 120 minutes). When the occupied bypass time expires, the unit  
transitions from occupied bypass mode to unoccupied mode. Pushing the  
CANCEL button cancels the timed override request. A timed override can-  
cel request will end the timed override before the occupied bypass time  
has expired and will transition the unit from occupied bypass mode to  
unoccupied mode.  
If the controller is in any mode other than unoccupied when the ON but-  
ton is pressed, the controller still starts the occupied bypass timer with-  
out changing the mode to occupied bypass. If the controller is placed in  
unoccupied mode before the occupied bypass timer expires, the controller  
will be placed in occupied bypass mode and remain in that mode until  
either the CANCEL button is pressed on the Trane zone sensor or the occu-  
pied bypass time expires.  
CNT-SVX07C-EN  
37  
 
       
Chapter 5 Sequence of operations  
Zone temperature control  
The Tracer ZN521 zone controller uses two methods of zone temperature  
control:  
Cascade zone control—used in the occupied, occupied bypass, and  
occupied standby modes  
Simplified zone control—used in the unoccupied mode  
Cascade zone control  
Cascade zone control maintains zone temperature by controlling the dis-  
charge air temperature to control the zone temperature. The controller  
uses the difference between the measured zone temperature and the  
active zone temperature setpoint to produce a discharge air temperature  
setpoint. The controller compares the discharge air temperature setpoint  
with the discharge air temperature and calculates a unit heating/cooling  
capacity accordingly (see Figure 18). The end devices (outdoor air damper,  
valves, etc.) operate in sequence based on the unit heating/cooling capac-  
ity (0–100%).  
Figure 18. Cascade zone control  
Calculated  
Calculated unit  
heating/cooling  
capacity  
discharge air  
temperature  
setpoint  
Active zone  
temperature  
setpoint  
Difference  
Difference  
Measured  
zone  
temperature  
Measured  
discharge air  
temperature  
If the discharge air temperature falls below the Discharge Air Control  
Point Low Limit (configurable using the Rover service tool) and cooling  
capacity is at a minimum, available heating capacity will be used to raise  
the discharge air temperature to the low limit (see “Discharge air temper-  
Simplified zone control  
In the unoccupied mode, the controller maintains the zone temperature  
by calculating the required heating or cooling capacity (0–100%) accord-  
ing to the measured zone temperature and the active zone temperature  
setpoint. The active zone temperature setpoint is determined by the cur-  
rent operating modes, which include occupancy and heat/cool modes.  
38  
CNT-SVX07C-EN  
 
         
Discharge air tempering  
Discharge air tempering  
If the controller is in cooling mode, cascade zone control initiates a dis-  
charge air tempering function when the discharge air temperature falls  
below the Discharge Air Control Point Low Limit (configurable using the  
Rover service tool) and all cooling capacity is at a minimum. The dis-  
charge air tempering function allows the controller to provide heating  
capacity (if available) to raise the discharge air temperature to the Dis-  
charge Air Control Point Low Limit.  
The discharge air tempering function is often initiated under the follow-  
ing circumstances: Cold outdoor air is brought in through the outdoor air  
damper when the damper is at (a high) minimum position, causing the  
discharge air temperature to fall below the Discharge Air Control Point  
Low Limit.  
Morning warm-up  
The morning warm-up feature is initiated when the controller is in tran-  
sition from unoccupied to occupied mode and the zone temperature is 3°F  
(1.7°C) below the occupied heating setpoint. The fan will be turned on and  
the outdoor air damper will remain closed. The damper modulates  
between closed and minimum position when the zone temperature is  
2–3°F (1.2–1.7°C) below the active heating setpoint. When the zone tem-  
perature reaches the occupied heating setpoint, the controller begins  
operating in the occupied mode.  
Morning cool-down  
The morning cool-down feature is initiated when the controller is in tran-  
sition from unoccupied to occupied and the zone temperature is 3°F  
(1.7°C) above the occupied heating setpoint. The fan will be turned on and  
the outdoor air damper will remain closed. The damper modulates  
between closed and minimum position when the zone temperature is  
2–3°F (1.2–1.7°C) above the active cooling setpoint. When the zone tem-  
perature reaches the occupied heating setpoint, the controller begins  
operating in the occupied mode.  
Heating or cooling mode  
The heating or cooling mode can be determined in one of two ways:  
By a communicated signal from a BAS or a peer controller  
Automatically, as determined by the controller  
A communicated heating signal permits the controller to heat only. A  
communicated cooling signal permits the controller to cool only. A com-  
municated auto signal allows the controller to automatically change from  
heating to cooling and vice versa.  
CNT-SVX07C-EN  
39  
 
               
Chapter 5 Sequence of operations  
In heating and cooling mode, the controller maintains the zone tempera-  
ture based on the active heating setpoint and the active cooling setpoint,  
respectively. The active heating and cooling setpoints are determined by  
the occupancy mode of the controller.  
For two-pipe and four-pipe changeover units, normal heat/cool operation  
will not begin until the ability to conduct the desired heating or cooling  
operation is verified. This is done using the entering water temperature  
sampling function, for which a valid entering water temperature is  
required. When neither a hard-wired nor a communicated entering water  
temperature value is present on changeover units, the controller will  
operate in heating mode only and assume the coil water is hot. The sam-  
pling function is not used.  
The entering water temperature sampling function is used only for  
changeover applications. It is used for information and troubleshooting  
only and does not affect the operation of the controller. (For more informa-  
Entering water temperature sampling  
function  
The entering water temperature sampling function is used with two-pipe  
and four-pipe changeover units and requires a valid entering water tem-  
perature value. If the entering water temperature value is less than 5°F  
(2.8°C) above a valid zone temperature value for hydronic heating and  
greater than 5°F (2.8°C) below a valid zone temperature value for  
hydronic cooling, the sampling function is enabled. When the sampling  
function is enabled, the controller opens the main hydronic valve to allow  
the water temperature to stabilize. After 3 minutes, the controller again  
compares the entering water temperature value to the zone temperature  
value to determine if the desired heating or cooling function can be  
accomplished. If the entering water temperature value remains out of  
range to accomplish the desired heating/cooling function, the controller  
closes the main hydronic valve and waits 60 minutes to attempt another  
sampling. If the entering water temperature value falls within the  
required range, it resumes normal heating/cooling operation and disables  
the sampling function.  
Fan operation  
The Tracer ZN521 supports up to three fan speeds. Every time the fan is  
enabled, the fan will begin operation and run on high speed for a period of  
time (0.5 seconds for fan coils and 3 seconds for unit ventilators and  
blower coils) before changing to any other speed. This is done to provide  
adequate torque to start the fan motor from the off position. The fan will  
always operate continuously while either heating or cooling during occu-  
pied, occupied standby, and occupied bypass operation. During unoccu-  
pied operation, the fan will cycle between off and high regardless of the  
40  
CNT-SVX07C-EN  
 
       
Exhaust control  
fan configuration. The controller can be configured to auto, to a specific  
fan speed, or to off. If both a communicated and hard-wired value (fan-  
speed switch) is present, the communicated value has priority.  
Note:  
In occupied mode, The Tracer ZN521 zone controller requires  
continuous fan operation because of cascade zone control. In  
unoccupied mode, the fan cycles.  
When the controller receives a communicated auto signal (or the associ-  
ated fan-speed switch is set to AUTO with no communicated value  
present), the fan will operate in the auto mode. In the auto mode, the fan  
will operate according to the fan default (configurable using the Rover  
service tool). The fan speed can be configured to default to auto, a specific  
speed, or off for both heating and cooling operation.  
Configured as auto and with multiple speeds available, the fan will auto-  
matically switch speeds depending on the difference between the zone  
temperature and the active zone temperature setpoint. The fan speed will  
increase as the difference increases and decrease as the difference  
decreases.  
When the controller receives a communicated fan-speed signal (high,  
medium, low) or the associated fan-speed switch is set to a specific fan  
speed, the fan will run continuously at the desired fan speed during occu-  
pied, occupied standby, and occupied bypass operation. During unoccu-  
pied operation, the fan will cycle between off and high regardless of the  
communicated fan-speed signal or fan-speed switch setting (unless either  
of these is off, which will control the fan off).  
The fan will turn off when the controller receives a communicated off sig-  
nal, when the fan-speed switch is set to OFF, when specific diagnostics are  
generated, or when the default fan speed is set to off and the fan is oper-  
ating in the auto mode.  
The ability to enable or disable the controller’s associated fan speed  
switch is configurable.  
Exhaust control  
Exhaust control is accomplished by a single-speed exhaust fan or a two-  
position exhaust damper. BOP2 controls this function. To enable exhaust  
control, configure the controller by selecting Exhaust Fan/Damper  
Present and by selecting the number of fan speeds as either One or Two.  
The exhaust function is coordinated with the supply fan and outdoor/  
return air dampers as follows:  
The exhaust output is energized only when the supply fan is operat-  
ing and the outdoor air damper position (%) is greater than or equal  
to the Exhaust Fan/Damper Enable Setpoint (configurable using the  
Rover service tool).  
CNT-SVX07C-EN  
41  
 
   
Chapter 5 Sequence of operations  
The exhaust output is de-energized if the outdoor air damper position  
drops 10% below the Exhaust Fan/Damper Enable Setpoint.  
If the Exhaust Fan/Damper Enable Setpoint is less than 10%, the  
exhaust output is energized if the outdoor air damper position is at  
the setpoint and de-energized at 0.  
Valve operation  
The Tracer ZN521 zone controller supports one or two tri-state modulat-  
ing or two-position valves, depending on the application (see Table 8). The  
controller opens and closes the appropriate valve(s) to maintain the active  
zone temperature setpoint at the heating setpoint in heating mode or the  
cooling setpoint in cooling mode (see “Cascade zone control” on page 38).  
For face-and-bypass applications, one or two isolation valves are  
controlled.  
Table 8. Valve control options  
Application  
Tri-st ate  
modulating  
Isolation  
(two-position)  
Two-position  
Hydronic/steam fan coils and blower coils  
Unit ventilators with valve control  
Face-and-bypass unit ventilators  
×
×
×
×
Modulating valve operation  
The Tracer ZN521 supports tri-state modulating valve control. Two  
binary outputs control each valve: one to drive the valve open and one to  
drive the valve closed. The stroke time for each valve is configurable  
using the Rover service tool. The controller supports heating, cooling, or  
heat/cool changeover with a single valve/coil for two-pipe applications.  
The controller supports cooling or heat/cool changeover with the main  
valve/coil and heating only with the auxiliary valve/coil for four-pipe  
applications. The controller moves the modulating valve to the desired  
positions based on heating or cooling requirements.  
Modulating valve calibration  
Calibration of modulating valves is done automatically. During normal  
operation, the controller overdrives the actuator (135% of the stroke time)  
whenever a position of 0% or 100% is requested. as part of Tracer ZN521  
normal operation. At power-up or after a power outage, the controller first  
drives all modulating valves (and dampers) to the closed position. The  
controller calibrates to the fully closed position by overdriving the actua-  
tor (135% of the stroke time). Then, the controller resumes normal  
operation.  
42  
CNT-SVX07C-EN  
 
             
Modulating outdoor/return air dampers  
Two-position valve operation  
The Tracer ZN521 supports two-position valves with a single binary out-  
put for each valve. Controllers used for two-pipe applications support  
heating, cooling, or heat/cool changeover with a single valve/coil. Control-  
ler used for four-pipe applications support cooling or heat/cool changeover  
with a main valve/coil, and heating only with an auxiliary valve/coil.  
Isolation-valve operation  
Two-pipe operation  
For two-pipe applications, the Tracer ZN521 can be configured as heating  
only, cooling only, or heat/cool changeover. The coil can be used as the pri-  
mary heating source and/or the primary cooling source. If present, an  
electric heating element can be used only as the primary heating source  
(instead of hydronic or steam heating). A changeover unit requires a valid  
entering water temperature value—either communicated or hard-wired—  
Four-pipe operation  
For four-pipe applications, the Tracer ZN521 can be configured as heat/  
cool or heat/cool changeover. The main coil can be used as the primary  
cooling source or the primary heating/cooling source. The auxiliary coil  
can be used only as the primary heating source, not as a second stage of  
heating. During normal operation, the controller never uses the main coil  
and auxiliary coil simultaneously. A changeover unit requires a valid  
entering water temperature value—either communicated or hard-wired—  
tric heat control is not available on four-pipe applications.  
Modulating outdoor/return air dampers  
The Tracer ZN521 operates the modulating outdoor/return air dampers  
according to the following factors:  
Occupancy mode  
Outdoor air temperature (communicated or hard-wired sensor)  
Zone temperature  
Setpoint  
Discharge air temperature  
Discharge air temperature setpoint  
The minimum position for an outdoor air damper is configurable using  
the Rover service tool for occupied and occupied standby modes and for  
CNT-SVX07C-EN  
43  
 
                     
Chapter 5 Sequence of operations  
low-speed fan operation. A controller can also receive a BAS-communi-  
cated outdoor air damper minimum position.  
A BAS-communicated minimum position setpoint has priority over all  
locally configured setpoints. When a communicated minimum position  
setpoint is not present, the controller uses the configured minimum posi-  
tion for low fan speed whenever the fan is running at low speed, regard-  
less of the occupancy state. See Table 9 and Table 10 for more information  
about how the controller determines the position of the modulating out-  
door air damper.  
Table 9. Modulating outdoor air damper position setpoint determination  
BAS-communicated  
Occupancy  
Fan speed  
Any value  
Active minimum setpoint  
0% (closed)  
setpoint  
Any value  
Unoccupied  
Occupied  
Valid  
Any value  
BAS-communicated  
Occupied bypass  
Occupied standby  
Occupied  
Invalid  
Low  
Occupied low fan minimum  
Occupied bypass  
Occupied standby  
Occupied  
Occupied bypass  
Invalid  
Invalid  
Medium/high  
Medium/high  
Occupied minimum  
Occupied standby  
Occupied standby minimum  
Table 10. Relationship between outdoor temperature sensors and damper position  
Modulating outdoor air damper position  
Outdoor air temperature  
Occupied or occupied  
Occupied standby  
bypass  
Unoccupied  
No or invalid outdoor air  
temperature  
Open to occupied  
minimum position  
Open to occupied standby  
minimum position  
Closed  
Closed  
Failed outdoor air sensor  
Open to occupied  
minimum position  
Open to occupied standby  
minimum position  
Outdoor air temperature  
present and economizing  
possible1  
Economizing; damper  
controlled between  
occupied minimum  
position and 100%  
Economizing; damper  
controlled between  
occupied standby  
minimum position and  
100%  
Open and economizing  
during unit operation; oth-  
erwise closed  
Outdoor air temperature  
present and economizing  
not possible1  
Open to occupied mini-  
mum position  
Open to occupied standby  
minimum position  
Closed  
1
For an explanation of the economizing feature, see “Economizing (free cooling)” on page 45.  
44  
CNT-SVX07C-EN  
 
   
Modulating outdoor/return air dampers  
ASHRAE Cycle 1 conformance  
Tracer ZN521 applications with an outside air damper support ASHRAE  
Cycle 1 conformance. ASHRAE Cycle 1 operation admits 100% outdoor  
air at all times except during a warm-up cycle. A tri-state modulating  
damper actuator is required for this operation. For Tracer ZN521  
ASHRAE Cycle 1 conformance, configure the minimum position of the  
economizer setpoint to 100% open during occupied periods. If the zone  
temperature drops 3°F (1.7°C) below the active zone temperature set-  
point, the Tracer ZN521 closes the outdoor air damper regardless of the  
minimum position setpoint.  
ASHRAE Cycle 2 conformance  
Tracer ZN521 controller applications with modulating outside air damper  
support ASHRAE Cycle 2 conformance. ASHRAE Cycle 2 operation  
allows the modulating outdoor air damper to completely close when the  
zone temperature drops 3°F (1.7°C) or more below the active zone temper-  
ature setpoint. If the zone temperature rises to within 2°F (1.2°C) of the  
active setpoint, the damper opens to the occupied or occupied standby  
minimum damper positions. If the zone temperature is between 2°F and  
3°F (1.2°C and 1.7°C) below the active zone temperature setpoint, the  
damper modulates between the minimum position and closed.  
If the discharge air temperature is between the discharge air tempera-  
ture low limit and the discharge air temperature low setpoint, the  
damper modulates between the minimum position and closed. If this situ-  
ation is concurrent with ASHRAE Cycle 2 operation, the lesser of the two  
setpoints will determine the actual damper position.  
Economizing (free cooling)  
Cooling with outdoor air, when the temperature is low enough to make  
this possible, is referred to as economizing or free cooling. Tracer ZN521  
controller applications with modulating outside air damper support econ-  
omizing. The modulating outdoor air damper provides the first source of  
cooling for the Tracer ZN521. The controller initiates economizing if the  
outdoor air temperature is below the economizer enable point (config-  
urable using the Rover service tool). If economizing is initiated, the con-  
troller modulates the outdoor air damper (between the active minimum  
damper position and 100%) to control the amount of outdoor air cooling  
capacity. When the outdoor air temperature rises 5°F (2.8°C) above the  
economizer enable point, the controller disables economizing and moves  
the outdoor air damper back to its predetermined minimum position  
based on the current occupancy mode or communicated minimum outdoor  
air damper position. If an outdoor air temperature value is not present,  
economizing is disabled.  
CNT-SVX07C-EN  
45  
 
           
Chapter 5 Sequence of operations  
Two-position control of a modulating  
outdoor air damper  
The Tracer ZN521 does not support a two-position outdoor air damper  
actuator. However, a modulating outdoor/return air damper actuator can  
be used for two-position control. Two-position control can be accomplished  
by not providing an outdoor air temperature (neither hard-wired nor com-  
municated) to the controller, and by setting the damper minimum posi-  
tion (using the Rover service tool) to the desired value (typically, 100%).  
Face-and-bypass damper operation  
The Tracer ZN521 can control a face-and-bypass damper to modulate a  
percentage of air to the face of the coil(s) and around (bypass) the coil(s) to  
maintain zone comfort. For two-pipe changeover applications, if the con-  
troller requests heating and hot water is available, the face-and-bypass  
damper modulates to the face position. If the controller requests heating  
and hot water is not available, the face-and-bypass damper remains in  
the bypass position, and water sampling may be initiated (see “Entering  
changeover applications, both heat and cool capacity are assumed to be  
available.  
Face-and-bypass, isolation-valve operation  
A Tracer ZN521 with a face-and-bypass damper controls on/off isolation  
valve(s) to prevent unwanted water flow through the coil(s) when no air-  
flow is passing over the coil (100% bypass). In two-pipe applications, the  
isolation valve stops water flow, preventing radiant heat (heating mode)  
and excessive condensate (cooling mode) from the coil. In four-pipe appli-  
cations, the isolation valves are used to prevent simultaneous heating  
and cooling.  
The heating or cooling isolation valve opens whenever capacity is  
requested (>0%) as the face-and-bypass damper begins to modulate  
toward the coil face. The isolation valve closes when capacity returns to  
0%.  
DX cooling operation  
The Tracer ZN521 supports one stage of direct expansion (DX) compres-  
sor operation for cooling only.  
Note:  
The controller does not use the DX compressor and economizing  
simultaneously. Not doing so prevents short cycling from occur-  
ring if the entering air temperature is too low for the evapora-  
tor coil to operate as designed.  
46  
CNT-SVX07C-EN  
 
               
Electric heat operation  
Electric heat operation  
The Tracer ZN521 supports both single-stage and two-stage electric heat.  
Electric heat is cycled on and off to maintain the discharge air tempera-  
ture at the active heating setpoint. Two-pipe changeover units with elec-  
tric heat use the electric heat only when hot water is not available. The  
use of both electric and hydronic heat is not supported.  
Baseboard heat operation  
When configured for baseboard heat output, the controller turns on base-  
board heat at 2.2°F (1.2°C) below the active heating setpoint, and turns  
off baseboard heat at 0.8°F (0.4°C) below the active heating setpoint. The  
range for activating the baseboard heat cannot be adjusted; however, the  
heating setpoint is configurable using the Rover service tool.  
Baseboard heating is used most effectively when the discharge air tem-  
perature control high limit is set below 100°F (56°C). If this is done, the  
unit heat will maintain the temperature on light load days and the base-  
board heat will be enabled to maintain the temperature on heavier load  
days.  
Dehumidification  
The Tracer ZN521 supports a dehumidification feature. Dehumidification  
is possible if the following are present:  
Mechanical cooling is available  
The heating capacity is located in the reheat position  
A zone humidity sensor is connected at AI4, or a relative humidity  
(RH) value is transmitted to the controller by a BAS.  
The Space RH Setpoint is valid (configurable using the Rover service  
tool)  
Dehumidification is enabled using the Rover service tool  
The controller initiates dehumidification if the zone humidity exceeds the  
humidity setpoint. The controller continues to dehumidify until the  
sensed humidity falls below the setpoint minus the relative humidity off-  
set.  
The controller uses cooling and heating capacities simultaneously to  
dehumidify the space. While dehumidifying, the controller maintains the  
zone temperature at the active setpoint.  
Note:  
Dehumidification is not available for face-and-bypass applica-  
tions, and cannot be used if the unit is in the unoccupied mode.  
Dehumidification disables the economizing function.  
CNT-SVX07C-EN  
47  
 
             
Chapter 5 Sequence of operations  
Peer-to-peer communication  
Tracer ZN521 zone controllers have the ability to share data with other  
LonTalk-based controllers. Multiple controllers can be bound as peers,  
using the Rover service tool, to share:  
Setpoint  
Zone temperature  
Heating/cooling mode  
Fan status  
Unit capacity control  
Shared data is communicated from one controller to any other controller  
that is bound to it as a peer. Applications having more than one unit serv-  
ing a single zone can benefit by using this feature; it allows multiple units  
to share a single zone temperature sensor and prevents multiple units  
from simultaneously heating and cooling.  
Unit protection strategies  
The following strategies are initiated when specific conditions exist in  
order to protect the unit or building from damage:  
Smart reset  
Low-coil-temperature protection  
Condensate overflow  
Fan status  
Fan off delay  
Filter-maintenance timer  
Freeze avoidance  
Freeze protection (discharge air temperature low limit)  
48  
CNT-SVX07C-EN  
 
       
Unit protection strategies  
Smart reset  
The Tracer ZN521 will automatically restart a unit that is locked-out as a  
result of a Low Coil Temp Detection (BI1) diagnostic. Referred to as  
“smart reset,” this automatic restart will occur 30 minutes after the diag-  
nostic occurs. If the unit is successfully restarted, the diagnostic is  
cleared. If the unit undergoes another Low Coil Temp Detection diagnos-  
tic within a 24-hour period, the unit will be locked out until it is manually  
reset. (For more information on manual resetting, see “Manual (latching)  
Low-coil-temperature protection  
above.  
Condensate overflow  
Fan status  
The fan status is based on the status of the binary output(s) dedicated to  
fan control. The fan status is reported as high, medium, or low whenever  
the corresponding binary output is energized. The fan status is reported  
as off whenever none of the fan binary outputs are energized.  
Additionally, a fan-status switch can be connected to BI4 to monitor the  
status of the fan for belt-driven or direct-driven units. The fan status  
switch provides feedback to the controller. If the fan is not operating when  
the controller has the fan controlled to on, the controller will generate a  
Low AirFlow—Fan Failure diagnostic.  
If the controller energizes the fan output for 1 minute, and the fan status  
switch indicates no fan operation, the controller performs a unit shut-  
down and generates a Low AirFlow—Fan Failure diagnostic. If the fan  
has been operating normally for one minute, but the fan status switch  
indicates no fan operation, the same diagnostic is generated. This manual  
diagnostic discontinues unit operation until the diagnostic has been  
cleared from the controller. If a diagnostic reset is sent to the controller  
and the fan condition still exists, the controller attempts to run the fan for  
1 minutes before generating another diagnostic and performing a unit  
shutdown.  
Fan off delay  
After heating has been controlled off, the Tracer ZN521 keeps the fan  
energized for an additional 30 seconds. The purpose of this feature is to  
remove residual heat from the heating source.  
CNT-SVX07C-EN  
49  
 
                     
Chapter 5 Sequence of operations  
Filter-maintenance timer  
The filter-maintenance timer tracks the amount of time (in hours) that  
the fan is enabled. The Maintenance Required Timer Setpoint (config-  
urable using the Rover service tool) is used to set the amount of time until  
maintenance (typically, a filter change) is needed. If the setpoint is config-  
ured to zero, the filter-maintenance timer is disabled.  
The controller compares the fan-run time to Maintenance Required Timer  
Setpoint. Once the setpoint is reached, the controller generates a Mainte-  
nance Required diagnostic. When the diagnostic is cleared, the controller  
resets the filter-maintenance timer to zero, and the timer begins accumu-  
lating fan-run time again.  
Freeze avoidance  
Freeze avoidance is used for low ambient temperature protection. It is ini-  
tiated only when the fan is off. The controller enters the freeze-avoidance  
mode when the outdoor air temperature is below the Freeze Avoidance  
Setpoint (configurable using the Rover service tool). The controller dis-  
ables freeze avoidance when the outdoor air temperature rises 3°F (1.7°C)  
above the Freeze Avoidance Setpoint.  
When the controller is in freeze-avoidance mode:  
Valves are driven open to allow water to flow through the coil  
Fan is off  
Face-and-bypass damper (when present) is at full bypass  
Economizing is disabled  
The outdoor/return air damper is closed  
DX cooling is off  
Electric heat stages are off  
Freeze protection (discharge air temperature low limit)  
The controller monitors the discharge air temperature with a 10 kther-  
mistor wired to analog input AI2. The freeze-protection operation is initi-  
ated whenever the discharge air temperature falls below the Discharge  
Air Temperature Low Limit. The Discharge Air Temperature Low Limit  
is configurable using the Rover service tool. During freeze protection, the  
controller increases the heating capacity or decreases the cooling capacity  
in order to raise the discharge air temperature above the low limit. If the  
discharge air temperature remains below the low limit for 3 minutes, the  
controller generates a Discharge Air Temp Limit diagnostic. See Table 16  
on page 59 for the effects of this diagnostic on outputs.  
50  
CNT-SVX07C-EN  
 
                 
Chapter 6  
Status indicators for  
operation and  
communication  
This chapter describes the operation and communication status indica-  
tors on the Tracer ZN521 controller, including:  
A description of the location and function of the Test button and Ser-  
vice pin button and the light-emitting diodes (LEDs) located on the  
controller  
A complete list of the diagnostics that can occur, their effect on con-  
troller outputs, and an explanation of how diagnostics are cleared and  
the device restored to normal operation  
Test button  
The Test button is used to perform the manual output test (see “Manual  
output test” on page 52), which verifies that the controller output devices  
are operating properly. It is located on the Tracer ZN521 circuit board as  
shown in Figure 19. You must remove the cover to access the Test button.  
Figure 19. Tracer ZN521 zone controller circuit board  
Green (status)  
LED  
Test button  
Neuron ID label  
Red (service) LED  
Service pin button  
Yellow  
(communication)  
LED  
CNT-SVX07C-EN  
51  
 
               
Chapter 6 Status indicators for operation and communication  
Manual output test  
The manual output test sequentially turns on and off all binary outputs  
to verify their operation. The test overrides normal operation of the con-  
troller, which is suspended while the test is being performed.  
Use the manual output test to:  
Verify output wiring and operation  
Force the water valve(s) open to balance the hydronic system  
Clear diagnostics and restore normal operation (although not a pri-  
mary function of the manual output test)  
The manual output test is performed either by repeatedly pressing the  
Test button to proceed through the test sequence or by using the Rover  
service tool. Table 11 on page 53 lists the outputs for non-face-and-bypass  
unit configurations in the sequence in which they are verified; Table 12  
on page 55 lists the outputs for face-and-bypass unit configurations in the  
sequence in which they are verified.  
The procedure is as follows:  
1. Press and hold the Test button for 3 to 4 seconds, then release it to  
start the test mode. The green (status) LED goes off when you press  
the Test button, and then it blinks (as described in Table 14 on  
page 57) when the Test button is released to indicate that the control-  
ler is in manual test mode.  
2. Press the Test button (no more than once per second) to advance  
through the test sequence. Table 11 and Table 12 show the resulting  
activities of the binary outputs.  
Note:  
The outputs are not subject to minimum on or off times during  
the test sequence.  
52  
CNT-SVX07C-EN  
 
       
Manual output test  
a t d h a r e o b e  
2 ) B a s  
c i r n e 1 ) G  
o s e , c e l r p d a r m o o t r d u a O i  
n
, o p e e r  
d a r m p r o a i t d u o O  
e 2 a t g , s a t h i e c r t c  
2 ) E l e  
o s e c l e , l v a i n t g v 1 ) H e a  
e 1 a t g , s a t h i e c r t c  
3 ) E l e  
i t i o n p - o h o s e w a 2 ) T  
o e p , e l v a i n t g v 1 ) H e a  
e v l a v t  
n
e s o c l l v a e v ,  
r e v o e g a n h c n g / C o o l i  
o s r s e  
e v l a v e r  
D ) X 3 c o m p r  
n a g h e c o v  
l i n g /  
i t i o n p - o c o o s w o 2 ) T  
n e p o l v a e v ,  
r
o v e g e n a c / h g n i l o o C ) 1  
w o l n F a  
t
h a u s 2 ) E x  
d i u m n a m e 1 ) F  
h n i a g F h  
d s e e s p r i s n o t b u t s t e T  
s e m t f i e r b o m N u  
CNT-SVX07C-EN  
53  
 
 
Chapter 6 Status indicators for operation and communication  
a t d h a r e o b e  
2 ) B a s  
c i r n e 1 ) G  
o s e , c l e r p d a r m o o t r d u a O i  
n
, o p e e r  
d a r m p r o a i t d u o O  
e 2 a t g , s a t h i e c r t c  
2 ) E l e  
o s e c l e , l v a i n t g v 1 ) H e a  
e 1 a t g , s a t h i e c r t c  
3 ) E l e  
i t i o n p - o h o s e w a 2 ) T  
o e p , e l v a i n t g v 1 ) H e a  
e v l a v t  
n
e s o c l l v a e v ,  
n a g h e c o / v g n i l o o C  
e r  
o s r s e D ) X 3 c o m p r  
e v l a v e r  
n a g h e c o v  
i t i o n p - o c o o s w o 2 ) T  
l i n g /  
n e p o l v a e v ,  
o v e g e n a c / h g n i l o o C ) 1  
r
w o l n F a  
t
h a u s 2 ) E x  
d i u m n a m e 1 ) F  
h n i a g F h  
d s e e s p r i s n o t b u t s t e T  
s e m t f i e r b o m N u  
54  
CNT-SVX07C-EN  
 
Manual output test  
Table 12. Manual output test sequence for face-and-bypass configurations (two-position isolation valves  
only)  
Step Result  
BOP1  
BOP2  
BOP3  
BOP4  
BOP5  
BOP6  
BOP7  
BOP8  
BOP9  
BO  
1
Begins test  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
On/Close  
Off  
On/Close  
Off  
mode1  
Fan high2  
2
3
On/High  
Off  
Off  
Off  
Off  
On/Open  
On/Open  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Fan  
medium3  
Off  
1) On/Med  
2) Off  
Fan low4  
4
5
Off  
Off  
Off  
On/Low  
Off  
On/Open  
On/Open  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Main open,  
DX on  
On/High  
Off  
On/Open  
6
7
Main close,  
DX off, aux  
open  
On/High  
On/High  
Off  
Off  
Off  
Off  
Off  
On/Open  
On/Open  
On/Open  
On/Open  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Aux open,  
EH1 on,  
exhaust  
fan5  
1) Off  
2) On  
8
Aux close,  
damper  
open  
On/High  
On/High  
On/High  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
Off  
On/Close  
On/Close  
On/Close  
On/Open  
Off  
Off  
Off  
Off  
On  
9
Outdoor air  
damper  
close  
On/Close  
Off  
10  
Generic/  
baseboard  
heat  
energized6  
Off  
11: Exit5  
1
The controller turns off all fan and electric heat outputs and drives all dampers and valves closed.  
The controller attempts to clear all diagnostics.  
2
3
If configured for a 3-speed fan, the medium fan speed output will energize at step 3. If configured for a 2-speed fan, the fan remains on high  
at step 3.  
4
If configured for a 3-speed fan, the medium fan speed output energizes at step 4. If configured for a 2-speed fan, the low fan speed output en  
at step 4. If configured for a 1-speed fan, the fan remains on high speed at step 4.  
5
6
If the unit is configured for a 1- or 2-speed fan, the exhaust fan output energizes on step 7. The exhaust fan output is shared with medium fan  
After step 10, the manual output test performs an exit, which initiates a reset to restore the controller to normal operation.  
CNT-SVX07C-EN  
55  
 
 
Chapter 6 Status indicators for operation and communication  
Service pin button  
The Service pin button is located as shown in Figure 19 on page 51. The  
Service pin button is used to:  
Identify a device (see “Identifying a device” in the Rover Installation/  
Operation/Programming guide (EMTX-SVX01A-EN)  
Add a device to the active group (see “Adding a device” in EMTX-  
SVX01A-EN)  
Verify PCMCIA communications (see “Verifying PCMCIA communi-  
cations” in EMTX-SVX01A-EN)  
Make the green (status) LED “wink” to verify that the controller is  
communicating on the link (see Table 14 on page 57 and “Setting the  
Auto-wink option” in EMTX-SVX01A-EN)  
Interpreting LEDs  
The red (service) LED on the Tracer ZN521 controller (see Figure 19 on  
page 51) indicates whether the controller is capable of operating normally  
(see Table 13).  
Table 13. Red LED: Service indicator  
LED activity  
Explanation  
LED is off continuously when power  
is applied to the controller.  
The controller is operating normally.  
LED is on continuously when power  
is applied to the controller.  
The controller is not working prop-  
erly, or someone is pressing the Ser-  
vice pin button.  
LED flashes once every second.  
The controller is not executing the  
application software because the net-  
work connections and addressing  
have been removed.1  
1
Restore the controller to normal operation using the Rover service tool. Refer to  
EMTX-SVX01A-EN for more information.  
56  
CNT-SVX07C-EN  
 
                   
Interpreting LEDs  
The green (status) LED on the Tracer ZN521 controller (see Figure 19 on  
page 51) indicates whether the controller has power applied to it and if  
the controller is in manual test mode (see Table 14).  
Table 14. Green LED: Status indicator  
LED activity  
Explanation  
LED is on continuously.  
Power is on (normal operation).  
LED blinks (one recurring blink).  
Manual output test mode is being  
performed and no diagnostics are  
present.  
LED blinks (blinks twice as a recur-  
ring sequence).  
Manual output test mode is being  
performed and one or more diag-  
nostics are present.  
LED blinks (1/4 second on,  
1/4 second off for 10 seconds).  
The Auto-wink option is activated,  
and the controller is  
communicating.1  
LED is off continuously.  
Either the power is off,  
the controller has malfunctioned, or  
the Test button is being pressed.  
1
By sending a request from the Rover service tool, you can request the controllers  
green LED to blink (“wink”), a notification that the controller received the signal  
and is communicating.  
The yellow (communications) LED on the Tracer ZN521 controller (see  
Figure 19 on page 51) indicate the controller’s communication status (see  
Table 15. Yellow LED: Communications indicator  
LED activity  
Explanation  
LED is off continuously  
The controller is not detecting any  
communication (normal for stand-  
alone applications).  
LED blinks.  
The controller detects communica-  
tion (normal for communicating  
applications, including data sharing).  
LED is on continuously.  
Problem with communication link  
wiring (possible need for termination  
resistor), or controller failure (caused  
by power surge, lightning strike, etc.)  
CNT-SVX07C-EN  
57  
 
       
Chapter 6 Status indicators for operation and communication  
Diagnostics  
Diagnostics are informational messages that indicate the operational sta-  
tus of the controller. In response to most diagnostics, the controller  
attempts to protect the equipment by enabling or disabling, or opening or  
closing, specific outputs. Other diagnostics provide information about the  
status of the controller, but have no effect on outputs. Diagnostics are  
reported in the order in which they occur. Multiple diagnostics can be  
present simultaneously. Diagnostic messages are viewed using the Rover  
service tool or through a BAS.  
Types of diagnostics  
Diagnostics are categorized according to the type of clearing method each  
uses and the type of information each provides.  
The four categories are:  
Manual (latching)  
Automatic (nonlatching)  
Smart reset  
Informational  
Note:  
Clearing diagnostics refers to deleting diagnostics from the  
software; it does not affect the problem that generated the mes-  
sage. For help with diagnosing a problem, see Chapter 7, “Trou-  
Manual (latching) diagnostics  
Manual diagnostics (also referred to as latching) cause the unit to shut  
down. Manual diagnostics can be cleared from the controller in one of the  
following ways:  
By using the Rover service tool (see “Resetting a diagnostic” in  
EMTX-SVX01A-EN, Rover Installation/Operation/and Program-  
ming guide).  
Through a building automation system (see product literature)  
By initiating a manual output test at the controller (see “Manual out-  
By cycling power to the controller. When the 24 Vac power to the con-  
troller is cycled off and then on again, a power-up sequence occurs.  
By turning the zone sensor fan switch to OFF and then back to any  
other setting. (This feature will be available beginning with controller  
software version 2.10.)  
Automatic (nonlatching) diagnostics  
Automatic diagnostics clear automatically when the problem that gener-  
ated the diagnostic is solved.  
58  
CNT-SVX07C-EN  
 
                 
Diagnostics  
Smart reset diagnostics  
After the controller detects the first smart reset diagnostic, the unit waits  
30 minutes before initiating the smart reset function. If another diagnos-  
tic of this type occurs again within 24 hours after an automatic clearing,  
you must clear the diagnostic manually by using any of the ways shown  
Informational diagnostics  
Informational diagnostics provide information about the status of the  
controller. They do not affect machine operation. They can be cleared from  
the controller using any of the ways shown for “Manual (latching) diag-  
Table of diagnostics  
Table 16 The tables present each diagnostic that can be generated by the  
Tracer ZN521, its effect on outputs (consequences), and its type.  
Note:  
The generic binary output is unaffected by diagnostics.  
Table 16. Diagnostics  
Diagnostic  
Diagnostic  
Probable cause  
Consequences  
Fan unaffected  
Valves unaffected  
Electric heat unaffected  
type  
Maintenance Required  
Fan run hours exceed the  
time set to indicate filter  
change  
Informational  
Face and bypass damper unaffected  
Condensate Overflow  
The drain pan is full of  
water  
Fan off  
Valves closed  
Manual  
Outdoor air damper closed  
Face and bypass damper bypass  
DX/electric heat off  
Baseboard heat off  
Low Coil Temp Detection  
Low Airflow—Fan Failure  
The leaving fluid temper- Fan off  
Smart reset/  
Manual  
ature may be close to  
freezing  
Valves open  
Outdoor air damper closed  
Face and bypass damper bypass  
DX/electric heat off  
Baseboard heat off  
The fan drive belt, con-  
tactor, or motor has  
failed.  
Fan off  
Valves closed  
Outdoor air damper closed  
Face and bypass damper bypass  
DX/electric heat off  
Baseboard heat off  
Manual  
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59  
 
                         
Chapter 6 Status indicators for operation and communication  
Table 16. Diagnostics (Continued)  
Diagnostic  
type  
Diagnostic  
Probable cause  
Consequences  
Space Temperature Failure  
Invalid or missing value  
for zone temperature  
Fan off  
Valves closed  
Outdoor air damper closed  
Face and bypass damper bypass  
DX/electric heat off  
Automatic  
Automatic  
Automatic  
Automatic  
Automatic  
Baseboard heat off  
Entering Water Temp Failure Invalid or missing value  
for zone temperature  
Fan unaffected (enabled)  
Valves unaffected  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX/electric heat unaffected  
Baseboard heat off  
Discharge Air Temp Limit  
Discharge Air Temp Failure  
Outdoor Air Temp Failure  
Discharge air tempera-  
ture has fallen below the  
Discharge Air Tempera-  
ture Low Limit  
Fan off  
Valves open  
Outdoor air damper closed  
Face and bypass damper bypass  
DX/electric heat off  
Baseboard heat off  
Invalid or missing value  
for discharge air temper-  
ature  
Fan off  
Valves closed  
Outdoor air damper closed  
Face and bypass damper bypass  
DX cooling/electric heat off  
Baseboard heat off  
Invalid or missing value  
for outdoor air tempera-  
ture  
Fan unaffected  
Valved unaffected  
Outdoor air damper minimum  
position  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
Humidity Input Failure  
Invalid or missing value  
for relative humidity  
Fan unaffected  
Valves unaffected  
Automatic  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
Dehumidification sequence off  
CO Sensor Failure  
Invalid or missing value  
Fan unaffected  
Informational  
2
for CO  
Valves unaffected  
2
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
60  
CNT-SVX07C-EN  
 
           
Diagnostics  
Table 16. Diagnostics (Continued)  
Diagnostic  
Diagnostic  
type  
Probable cause  
Consequences  
Fan unaffected  
Generic AIP Failure  
Invalid or missing value  
for generic analog input  
Informational  
Automatic  
Automatic  
Informational  
Manual  
Valves unaffected  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
Local Fan Mode Failure  
Local Setpoint Failure  
Invalid or missing fan-  
speed switch (reverts to  
default fan speed)  
Fan unaffected  
Valves unaffected  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
Invalid or missing value  
Fan unaffected  
for zone temperature set- Valves unaffected  
point (reverts to default  
setpoint)  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
Generic Temperature Failure Invalid or missing  
Fan unaffected  
Valves unaffected  
Outdoor air damper unaffected  
Face and bypass damper unaffected  
DX cooling/electric heat unaffected  
Baseboard heat unaffected  
generic temperature  
value  
Invalid Unit Configuration  
Software is configured  
improperly  
Fan off  
Valves off  
Outdoor air damper closed  
Face and bypass damper closed  
DX cooling/electric heat off  
Baseboard heat off  
Normal  
On start-up  
Fan unaffected  
Automatic  
Valves unaffected  
Electric heat unaffected  
Compressors unaffected  
Damper unaffected  
CNT-SVX07C-EN  
61  
 
           
Chapter 6 Status indicators for operation and communication  
62  
CNT-SVX07C-EN  
 
Chapter 7  
Troubleshooting  
Use Table 17 through Table 22 to assist you in diagnosing any of the fol-  
lowing operational problems that you might encounter with the Tracer  
ZN521 zone controller:  
Fan does not energize (Table 17)  
Valves remain closed (Table 18 on page 64)  
Valves remain open (Table 19 on page 65)  
Compressors are not running (Table 20 on page 65)  
Electric heat does not energize (Table 20 on page 65)  
An outdoor air damper stays closed (Table 21 on page 66)  
An outdoor air damper stays open (Table 22 on page 66)  
Table 17. Fan does not energize  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the fan relays and contacts must be  
present and correct for normal fan operation. Refer to applicable wiring diagram.  
Failed end device  
Normal operation  
The fan motor and relay must be checked to ensure proper operation.  
The fan will turn off when the controller receives a communicated off signal, when the  
fan-speed switch is set to OFF, when specific diagnostics are generated, or when the  
default fan speed is set to Off and the fan is operating in the Auto mode. If the controller  
is in unoccupied mode, the fan cycles between off and the highest fan speed.  
No power to the con-  
troller  
If the controller does not have power, the unit fan does not operate. For the Tracer ZN521  
controller to operate normally, it must have an input voltage of 24 Vac. If the green LED is  
off continuously, the controller does not have sufficient power or has failed.  
Power-up control-wait  
If power-up control-wait is enabled (non-zero time), the controller remains off until one of  
two conditions occurs:  
1) The controller exits power-up control-wait after it receives communicated information.  
2) The controller exits power-up control-wait after the power-up control-wait time expires.  
Diagnostic present  
Unit configuration  
Several diagnostics affect fan operation. For information about these diagnostics, see  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, the fans may  
not work correctly.  
Manual output test  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the unit fan may not be on. Refer to the “Manual output test” on page 52.  
Random start  
observed  
After power-up, the controller always observes a random start from 5 to 30 seconds. The  
controller remains off until the random start time expires.  
CNT-SVX07C-EN  
63  
 
           
Chapter 7 Troubleshooting  
Table 17. Fan does not energize (Continued)  
Probable cause  
Explanation  
Cycling fan operation/  
continuous  
The controller operates the fan continuously when in the occupied, occupied standby, or  
occupied bypass mode. When the controller is in the unoccupied mode, the fan is cycled  
between high speed and off with capacity.  
Unoccupied operation  
Even if the controller is configured for continuous fan operation, the fan normally cycles  
with capacity during unoccupied mode. While unoccupied, the fan cycles on or off with  
heating/cooling to provide varying amounts of heating or cooling to the space.  
Fan mode off  
If a local fan mode switch determines the fan operation, the off position controls the fan  
off.  
Requested mode off  
You can communicate a desired operating mode (such as off, heat, and cool) to the con-  
troller. If off is communicated to the controller, the unit controls the fan off. There is no  
heating or cooling.  
Table 18. Valves remain closed  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the valve(s) must be present and correct  
for normal valve operation. Refer to applicable wiring diagram.  
Failed end device  
The valves must be checked to ensure proper operation.  
No power to the con-  
troller  
If the controller does not have power, the unit valve(s) will not operate. For the Tracer  
ZN521 controller to operate normally, you must apply an input voltage of 24 Vac. If the  
green LED is off continuously, the controller does not have sufficient power or has failed.  
Power-up control-wait  
If power-up control-wait is enabled (non-zero time), the controller remains off until one of  
two conditions occurs:  
1) The controller exits power-up control-wait after it receives communicated information.  
2) The controller exits power-up control-wait after the power-up control-wait time expires.  
Diagnostic present  
Several diagnostics affect valve operation. For information about these diagnostics, see  
Normal operation  
Unit configuration  
The controller opens and closes the valves to meet the unit capacity requirements.  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, the valves  
may not work correctly.  
Manual output test  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the valves may not be open. Refer to the “Manual output test” on page 52.  
Random start  
observed  
After power-up, the controller always observes a random start from 5 to 30 seconds. The  
controller remains off until the random start time expires.  
Requested mode off  
You can communicate a desired operating mode (such as off, heat, and cool) to the con-  
troller. If off is communicated to the controller, the unit controls the fan off. There is no  
heating or cooling.  
Entering water  
temperature  
sampling logic  
The controller includes entering water temperature sampling logic, which is automati-  
cally initiated during 2-pipe and 4-pipe changeover if the entering water temperature is  
either too cool or too hot for the desired heating or cooling. (See AI1: Entering water  
Valve configuration  
Make sure the valves are correctly configured, using the Rover service tool, as normally  
open or normally closed as dictated by the application.  
64  
CNT-SVX07C-EN  
 
   
Troubleshooting  
Table 19. Valves remain open  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the valve(s) must be present and correct  
for normal valve operation. Refer to applicable wiring diagram.  
Failed end device  
Normal operation  
Manual output test  
The valves must be checked to ensure proper operations.  
The controller opens and closes the valves to meet the unit capacity requirements.  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the values may not be open. refer to the “Manual output test” on page 52.  
Diagnostic present  
Unit configuration  
Several diagnostics affect valve operation. For information about these diagnostics, see  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, the valves may  
not work correctly.  
Entering water  
temperature  
sampling logic  
The controller includes entering water temperature sampling logic, which is automatically  
initiated during 2-pipe and 4-pipe changeover if the entering water temperature is either  
too cool or too hot for the desired heating or cooling. (See AI1: Entering water tempera-  
Valve configuration  
Freeze avoidance  
Make sure the valves are correctly configured, using the Rover service tool, as normally  
open or normally closed as dictated by the application.  
When the fan is off with no demand for capacity (0%) and the outdoor air temperature is  
below the freeze avoidance setpoint, the controller opens the water valves (100%) to pre-  
vent coil freezing. This includes unoccupied mode when there is no call for capacity or  
any other time the fan is off.  
Table 20. DX or electric heat does not energize  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the end devices must be present and cor-  
rect for normal operation. Refer to applicable wiring diagram.  
Failed end device  
Check the control contactors or the electric heat element, including any auxiliary safety  
interlocks, to ensure proper operation.  
No power to the  
controller  
If the controller does not have power, heat outputs do not operate. For the Tracer ZN521  
controller to operate normally, you must apply an input voltage of 24 Vac. If the green  
LED is off continuously, the controller does not have sufficient power or has failed.  
Diagnostic present  
Normal operation  
Several diagnostics affect DX and electric heat operation. For information about these  
The controller controls compressor or electric heat outputs as needed to meet the unit  
capacity requirements.  
Unit  
configuration  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, DX or electric  
heat may not operate correctly.  
Manual output test  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the DX or electric heat outputs may be off. Refer to the “Manual output test”  
CNT-SVX07C-EN  
65  
 
     
Chapter 7 Troubleshooting  
Table 20. DX or electric heat does not energize (Continued)  
Probable cause  
Explanation  
Requested mode off  
You can communicate a desired operating mode (such as off, heat, and cool) to the con-  
troller. If off is communicated to the controller, the unit shuts off the compressor or elec-  
tric heat.  
Freeze avoidance  
When the fan is off with no demand for capacity (0%) and the outdoor air temperature is  
below the freeze avoidance setpoint, the controller disables compressors and electric  
heat outputs (100%) to prevent coil freezing. This includes unoccupied mode when there  
is no call for capacity or any other time the fan is off.  
Table 21. Outdoor air damper remains closed  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the outdoor air damper must be present  
and correct for normal outdoor air damper operation. Refer to applicable wiring diagram.  
Failed end device  
Check damper actuator to ensure proper operation.  
No power to the  
controller  
If the controller does not have power, the outdoor air damper does not operate. For the  
Tracer ZN521 controller to operate normally, you must apply an input voltage of 24 Vac. If  
the green LED is off continuously, the controller does not have sufficient power or has  
failed.  
Diagnostic present  
Several diagnostics affect outdoor air damper operation. For information about these  
Normal  
operation  
The controller opens and closes the outdoor air damper based on the controller’s occu-  
pancy mode and fan status. Normally, the outdoor air damper is open during occupied  
mode when the fan is running and closed during unoccupied mode.  
Unit configuration  
Manual output test  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, the outdoor air  
damper may not work correctly.  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the outdoor air damper may not be open. Refer to the “Manual output test” on  
Warm-up and cool-  
down sequence  
The controller includes both a morning warm-up and cool-down sequence to keep the  
outdoor air damper closed during the transition from unoccupied to occupied. This is an  
attempt to bring the space under control as quickly as possible.  
Requested mode off  
You can communicate a desired operating mode (such as off, heat, or cool) to the control-  
ler. If off is communicated to the controller, the unit closes the outdoor air damper.  
Table 22. Outdoor air damper remains open  
Probable cause  
Explanation  
Unit wiring  
The wiring between the controller outputs and the outdoor air damper must be present  
and correct for normal outdoor air damper operation. Refer to applicable wiring diagram.  
Failed end device  
Check damper actuator to ensure proper operation.  
66  
CNT-SVX07C-EN  
 
     
Troubleshooting  
Table 22. Outdoor air damper remains open (Continued)  
Probable cause  
Explanation  
Normal  
operation  
The controller opens and closes the outdoor air damper based on the controller’s occu-  
pancy mode and fan status. Normally, the outdoor air damper is open during occupied  
mode when the fan is running and closed during unoccupied mode. (See “Modulating  
Unit  
configuration  
The controller must be properly configured based on the actual installed end devices and  
application. If the unit configuration does not match the actual end device, the outdoor air  
damper may not work correctly.  
Manual output test  
The controller includes a manual output test sequence you can use to verify output oper-  
ation and associated output wiring. However, based on the current step in the test  
sequence, the outdoor air damper may be open. Refer to the “Manual output test” on  
CNT-SVX07C-EN  
67  
 
 
Chapter 7 Troubleshooting  
68  
CNT-SVX07C-EN  
 
Index  
Numerics  
B
Baseboard heat  
A
BI1 (Low-coil-temperature  
Actuators  
Addressing  
AI1 (Entering water temperature),  
AI4 configured for CO2  
C
AI4 configured for RH  
CE, see Agency listing/compliance  
CO2  
Condensate overflow  
ASHRAE Cycle 1  
ASHRAE Cycle 2  
Configuration options  
AI3 (Outdoor air temperature or  
AI4 (Generic, CO2 measurement, or  
CNT-SVX07C-EN  
39  
 
 
Index  
G
Generic  
Discharge air temperature  
Discharge air temperature low limit,  
Generic temperature failure  
D
Dampers  
DX cooling  
H
Humidity  
E
Electric heat  
I
Device addressing for BAS  
Entering water temperature  
Diagnostics  
Invalid unit configuration  
F
L
Fan  
LEDs  
Interpreting yellow  
Local fan mode input failure  
Fan status  
LonTalk communication  
Free cooling, see Economizing  
LonTalk protocol, see LonTalk  
communication  
40  
CNT-SVX07C-EN  
 
Index  
Low-coil-temperature detection  
P
M
Modulating outdoor/return air  
Modulating valves  
protection strategies  
Mounting  
R
Two-position damper control,  
Two-position valve operation,  
43  
Rover service tool  
N
Verifying LonTalk  
Verifying PCMCIA  
Neuron IDs  
Smart reset  
S
Specifications  
Sensor  
LonTalk communication wiring  
O
Occupancy  
Sensors  
Discharge air temperature low  
Status indicators for operation and  
communication  
Outdoor air damper  
Outdoor air temperature  
Yellow (communication) LEDs,  
57  
CNT-SVX07C-EN  
41  
 
Index  
Switching devices  
V
Z
Valves  
Zone humidity  
Zone temperature  
Zone temperature failure  
T
Temperature sensors  
W
Water and duct temperature  
Troubleshooting  
Wiring  
Electric heat unit with DX  
U
UL, see Agency listing/compliance  
Four-pipe heating/cooling unit  
Four-pipe heating/cooling unit  
33  
Four-pipe hydronic heating/  
Two-pipe heating unit with DX  
Two-pipe heating/cooling unit  
32  
Two-pipe hydronic heating/  
changeover, 25  
Unit protection strategies  
Discharge air temperature low  
Low-coil-temperature  
Two-pipe hydronic-cooling unit,  
Two-pipe hydronic-heating unit,  
42  
CNT-SVX07C-EN  
 
 
Literature Order Number  
File Number  
CNT-SVX07C-EN  
SV-ES-BAS-CNT-SVX-07C-EN 0405  
CNT-SVX07B-EN October 2001  
Inland  
Supersedes  
Trane  
Stocking Location  
A business of American Standard Companies  
For more information contact your local Trane  
office or e-mail us at comfort@trane.com  
Trane has a policy of continuous product and product data improvement and reserves the right to  
change design and specifications without notice. Only qualified technicians should perform the installa-  
tion and servicing of equipment referred to in this publication.  
 

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