Trane VariTrac Changeover Bypass VAV Systems Thermostat User Manual


VAV Systems  
Order No.: VAV-SLM002-EN  
Date: March 2002  
The VariTrac History  
Trane brought their expertise in variable air volume (VAV) controls into  
the changeover-bypass zoning market with the introduction of VariTrac in  
1989. The concept of changeover-bypass zoning brings the flexibility  
and comfort of VAV systems into the light commercial unitary market, at  
an affordable price.  
The first generation of VariTrac was a 16-zone pressure dependent  
system. The zone dampers featured the same electronic zone controller  
Trane developed for its VAV boxes, operating in the pressure dependent  
mode. The heart of the system was the Comfort Manager™; a panel  
which was designed to manage the HVAC unit, bypass damper  
functions, and changeover decisions. The functional concept of this  
original system continues to be the backbone of today’s zoning system.  
In the early 90s, two important enhancements were added to the system:  
Trane’s new Comm 4 communications link for the damper controllers  
The ability to directly communicate with Trane’s new Voyager UCP  
electronic rooftop unit controls  
In 1995, Trane introduced the second generation of VariTrac. This  
generation featured the central control panel (CCP) as the functional  
replacement for Comfort Manager. The new panel featured a resin  
enclosure, optional relay board for 24 VAC unit control, and the move to  
static pressure for bypass control. Improved changeover control was  
added to the operating system, and the zone damper controls were  
upgraded to UCM Version 3.  
Now, in 2002, Trane introduces the next generation of VariTrac controls  
which includes all the great features of the original VariTrac system, plus  
new features and enhancements. The enhancements are designed to  
make this generation of VariTrac the simplest changeover-bypass zoning  
system to install, commission, and service of any light commercial  
controls system available today.  
The History of VariTrac................................................. 2  
Introduction................................................................... 4  
Why Changeover Bypass VAV ............................ 4  
The Delivered Systems Concept.......................... 5  
Feature and Benefits..................................................... 6  
Product Changes at a Glance .............................. 6  
Hardware Overview.............................................. 7  
VariTrac Function Overview................................. 8  
Application Considerations ....................................... 10  
Customers Identification............................................ 11  
Building Owners ................................................. 11  
Consulting Engineers ......................................... 11  
Contractors......................................................... 12  
Trane Sales Offices............................................ 12  
Selling VariTrac Systems ........................................... 13  
Competition................................................................. 13  
Why Changeover-Bypass VAV  
Packaged unitary systems offer one of today’s most popular and cost-  
effective methods for supplying conditioned air to small commercial  
buildings. The unitary machine most commonly used has a constant  
volume fan with a fixed outside air damper and a single thermostat.  
While this may meet the thermal requirements of the space, it may not  
meet all the comfort requirements of the space using a single thermostat  
for control.  
Changeover-bypass VAV is a design solution for this problem. As the  
name implies, these systems deliver a varying volume of air to multiple  
zones, each with its own thermostat, while still utilizing a unitary machine  
with a constant volume fan. Changeover-bypass-VAV combines the  
comfort benefits of VAV with the cost effectiveness of packaged unitary  
The light commercial HVAC marketplace is known for its high level of  
competition. Knowing how to position Trane’s zoning products against  
the competition is critical. Over the past couple of years, Trane has  
added “value” items to its standard product package. In many instances,  
competitors must resort to add-ons or upgraded systems to achieve  
similar operating results or benefits obtained by Trane products.  
Learning how to leverage both Trane’s value over the competition and  
defend against perceived competitor advantage is vital to the company’s  
light commercial business and obtaining increased market share.  
This marketing guide is designed to help sales personnel prepare for  
effective selling of the redesigned VariTrac changeover-bypass zoning  
By utilizing an existing product to new product comparison, Trane’s  
advantage in areas such as value, flexibility, and integrated controls will  
be explained. This enables the sales force to arm themselves with  
superior product knowledge of Trane’s zoning systems and their  
The Delivered Systems Concept  
Delivered products represent approximately eighty percent of the light  
commercial building market. The term delivered product refers to the  
relationship between the manufacturer and the contractor. The  
relationship is often limited to the sale and delivery of the product. The  
contractor takes full responsibility for installation and service. Delivered  
products contrast with applied products, for which the relationship  
between manufacturer and contractor extends to product selection,  
installation, commissioning, programming, and on-going service support.  
Opportunities for Trane to participate in the light commercial market for  
delivered products have never been as plentiful as they are today. The  
relationships that you foster and maintain with your contractors are  
essential to your success in increasing your VariTrac market share.  
Training your contractors to become self-sufficient in selling, applying,  
installing, and servicing VariTrac systems requires that you invest time to  
train them. The potential return on your investment is well worth the  
time. This relationship, in which you represent Trane as both supplier  
and educator, is your business opportunity.  
Features and Benefits  
The primary advantage of Trane’s zoning systems is that they are  
completely integrated systems with Trane’s unitary equipment. Another  
benefit is that these systems are so simple to install, operate and  
service, that contractors and installers can take advantage of the  
delivered concept versus the applied world of design, engineering, and  
programming. For more information, refer to the table below which  
describes and compares the features and benefits of Trane’s newest  
changeover-bypass VAV offering to the existing product.  
Product Changes at a Glance  
VariTrac II  
New VariTrac III  
CCP with 3 piece enclosure design and optional Operator Display  
Optional relay board with installation kit  
Quick snap-in optional relay board with easy to wire terminal strip  
Duct mounted pressure and temperature sensors hard  
wired back to the CCP  
Communicating sensor assembly including a UCM 4 with integral  
temperature and pressure sensor, and output to the bypass damper(s)  
Bypass damper hardwired back to the CCP  
Bypass damper with factory installed wiring harness for plug-in connection  
to communicating sensor assembly  
16 zones  
24 zones  
Zone dampers with UCM 3 boards  
Zone dampers with UCM 4 boards with:  
Zone occupancy sensor input  
Zone CO2 sensor input  
Round zone damper sizes:  
Added new rectangular zone dampers in sizes:  
8x12, 8x14, 8x16, 10x16, 10x20, 14x18  
6”, 8”, 10”, 12”, 14”, and 16”  
Comm 4 communications to the zone dampers  
Comm 3 communications to Tracker  
Same Comm 4 communications to the zone dampers for reliable  
operation and backward compatibility  
Supports Comm 5 communications to the new Tracker Version 10 panel  
PC edit terminal required for interfacing with the  
system (HyperTerminal)  
Optional touch-screen operator display with built in 7-day time clock .  
Windows based PC software.  
Round bypass damper sizes:  
Bypass dampers now come with factory installed wiring harness for plug-  
in connection to communicating sensor assembly  
6”, 8”, 10”, and 12”  
Rectangular bypass damper sizes:  
14x12, 16x16, 20x20, 30x20  
Manual analog zone sensors only  
Not applicable  
Digital display zone temperature sensor  
Zone occupancy sensor  
Not applicable  
Zone CO2 sensor  
Duct mount CO2 sensor  
Pressure independent boxes  
Add local heat  
Ability to use pressure independent boxes  
Ability to add local heat  
Hardware Overview  
Central Control Panel Enclosure  
The new VariTrac Central Control Panel (CCP) has a three-piece  
enclosure for simplified installation. All wiring is done on large, easily  
accessible terminal strips located in the wall mount base plate. The  
electronics are located in the middle section, which is snapped onto the  
base plate after mounting. The top section is either a blank face plate, or  
the optional operator display.  
Central Control Panel Operator Display  
The optional operator display (OD) is a back-lit liquid crystal display with  
touch-screen programming capability. Through the display you can  
access system status and zone status, and do basic set-up of the zone  
UCMs and the CCP system operating parameters. It is designed to give  
an installer the ability to commission a VariTrac system without requiring  
a PC. Additionally, the OD has a seven-day time clock built in to provide  
stand alone scheduling capability of the VariTrac system. Zones may be  
divided into four groups, each with its own schedule if desired. If there is  
no Tracker system on the job, the CCP must be ordered with a display.  
If Tracker is available, the CCP may have a blank cover plate installed  
instead of an OD. All set-up information for the CCP may then be  
accessed from the Tracker.  
Central Control Panel Optional Relay Board  
The new relay board does not require any mounting hardware or time  
consuming installation. It simply snaps into place. The terminal strip is  
now internally jumpered, so it may be wired directly to an HVAC unit low  
voltage terminal strip using the same terminal designations as an  
industry standard thermostat subbase.  
Communicating Sensor/Bypass Control Assembly  
The VariTrac duct sensors have been combined with a UCM into one  
factory-wired assembly, so it now resides on the Comm 4 link along with  
the zone dampers and Voyager/Precedent™ rooftop unit. The bypass  
damper is also wired to this assembly. This eliminates the multiple  
conductors and terminations between the CCP, the duct sensors and the  
bypass damper, where most installation errors occurred.  
Bypass Damper Installation Harness  
All bypass dampers will now be shipped with a 12-foot plenum-rated  
wiring harness attached to the damper at the factory. The harness has a  
polarized plug on the end which is plugged into the communicating  
sensor assembly control board. This eliminates bypass damper wiring  
errors during installation.  
Digital Display Zone Sensor  
The new digital display zone sensor has the look and functionality of the  
standard Trane zone sensor, but includes an LCD digital display of the  
space temperature and setpoint adjustment in degrees F or C. The  
sensor has ON and CANCEL buttons, and a communications jack which  
can be accessed without removing the cover. The sensor requires 24  
volts, and may share a power supply with UCM.  
Zone Occupancy Sensor  
The new zone occupancy sensor is a ceiling-mount infrared motion  
detector to be used with VariTrac zone damper UCM for controlling the  
occupied zone standby function. It can detect motion over a 360 degree  
range (adjustable) for up to a 1200 square foot area. It has SPDT  
isolated contacts for connection to the UCM occupancy input. The  
sensor requires 24 volts, and may share a power supply with UCM.  
Zone CO2 Sensor  
The zone CO2 sensor is a compact transmitter for use with the VariTrac  
UCM CO2 input for doing demand control ventilation. The sensor is a  
available in either wall- or duct-mount enclosures. The sensor requires  
24 volts, and may share a power supply with UCM.  
VariTrac PC Software  
Advanced set-up functions in VariTrac are now done with a new  
Windows®-based, graphical PC software program. Connection between  
the PC and the CCP is done with a standard serial port cable connection.  
VariTrac Function Overview  
Increased Zone Count  
The new VariTrac system now support 24 zones instead of 16. The  
zones may be VariTrac dampers, or any type of VariTrane VAV box  
including fan-powered boxes or boxes with factory-installed local heat.  
Automatic Configuration and Start-up  
The VariTrac system performs automatic configuration on start-up by  
locating all zone dampers or VAV boxes on the communications link and  
creating a database of zones, complete with default names. VariTrac  
takes control of all the zone dampers and calibrates them. It then  
calibrates the bypass system, establishes its own static pressure  
setpoint, and begins heating/cooling operation.  
Discharge Air Control  
VariTrac now does discharge air control. When there is a demand for  
heating or cooling from a zone, the CCP will control the discharge air  
temperature to the discharge air setpoint default (55°F cooling, 110°F  
heating), using as many stages as necessary. This allows VariTrac to do  
true capacity control under part-load conditions, and better manage the  
load created by increased ventilation air requirements.  
Supply Air Tempering  
It is now possible to enable the Supply Air Tempering function in a  
Voyager via the CCP. This allows the Voyager to cycle a stage of heat  
on and off to warm up the supply air stream and better manage the load  
created by increased ventilation air requirements.  
CO2 Based Demand Control Ventilation  
CO2 sensors many now be connected to VariTrac zone UCMs. Up to  
one sensor per zone on the system may be applied. The CCP Demand  
Control Ventilation configuration screen allows you to set a minimum  
ventilation damper position for the Voyager/Precedent unit, and a  
maximum ventilation damper position. You also configure a normal CO2  
setting and an alarm CO2 setting. As the CO2 rises between the normal  
setpoint and the alarm setpoint, the CCP resets the damper position to  
increase ventilation. The CCP can be configured to gather CO2  
measurements from one specific sensor, or to gather information from all  
the sensors on the system and select the highest value.  
Zone Occupied Standby Function  
A VariTrac UCM can now have an occupancy sensor connected to it,  
and can be configured to perform an occupied standby function. This  
mode is available whenever the VariTrac system is in the occupied  
mode. The zone will be in standby using its unoccupied setpoints if  
motion is not detected by the zone occupancy sensor. When motion is  
detected in the space, the UCM shifts to its occupied setpoints, and will  
remain that way until 30 minutes (adjustable) after motion ceases.  
System Balance Mode  
A VariTrac system can be placed in the balance mode from the operator  
display or the PC software using a single button selection. In this mode,  
the CCP automatically prepares the VariTrac system for balancing by  
starting the supply fan, disabling heating and cooling, closing the bypass  
damper, and opening all zone dampers to their maximum position. The  
system can then be balanced as a single zone system using mechanical  
hand balancing dampers.  
Global Sensor Setpoint Limit Set-up  
If the zone setpoint thumbwheels are enabled, their functional range  
should be limited to about a 5 degree span to avoid nuisance  
changeover. This requires you to access each individual UCM and  
manually adjust the limits. The new VariTrac CCP allows you to create a  
single set of limits, and then broadcast them to all the zones on the  
system at one time by pushing a single button.  
Application Considerations for  
A building with varying loads due to occupancy, time-of-day, or other  
special needs is a likely candidate for a changeover-bypass VAV system.  
Also, any structure required to meet the higher ventilation requirements  
associated with ASHRAE Standard 62 is a prime target. These  
applications include:  
Offices and small manufacturing buildings – Varying occupancy  
places varying demands on the HVAC system.  
Schools – Heightened concerns about indoor air quality (IAQ) affect  
both new and existing applications.  
Strip malls, movie theaters, health clubs – Variable vacancy and  
special needs for conditioned air apply in these buildings.  
Clinics, nursing homes, small hospitals – These buildings can be  
multi-purpose and almost always have special requirements for  
conditioned air.  
Customer Identification  
In technical sales, it is important to understand the answer to a  
fundamental question: Who needs this product and why?  
Ideal customers for VariTrac changeover-bypass VAV systems include:  
customers with buildings having significant variable occupancy  
(schools, office buildings, etc.)  
customers with buildings that want better tenant comfort, at a  
reasonable price  
building owners or facility managers that receive constant complaints  
about hot or cold areas in their building  
customers with buildings operating in locations requiring compliance  
with IAQ codes and standards.  
customers that value Trane’s ability to bring a simple, pre-  
engineered, integrated solution to the job  
Regardless of the customer, Trane’s message to the marketplace is that  
it is the entire packaged comfort system that matters, not the parts and  
pieces of one manufacturer over another.  
Building Owners  
Most building owners readily understand the concept of “total cost of  
ownership.” They are concerned not only with the first cost of their  
building’s HVAC system, but also with the on-going operating costs  
associated with that equipment. Trane’s changeover-bypass VAV  
system can reduce both first cost and the on-going operating costs  
normally associated with a larger, more complex system.  
Consulting Engineers  
With the increasingly rapid changes in technology, engineers are  
pressed to keep up with the more complex building codes and standards,  
let alone, the control systems that must adhere to these measures. With  
Trane’s changeover-bypass VAV, the systems are simple, yet they  
address customers’ concerns regarding the latest issues with IAQ.  
Local, state, and federal building codes increasingly set forth  
requirements that are associated with adherence to ASHRAE 62 to  
assure that IAQ is a design requirement, especially for new construction.  
As a result, consulting engineers are looking for proven ways to address  
the IAQ issue.  
The first cost benefits associated with Trane’s changeover-bypass-VAV  
systems are important to contractors because:  
at the top of their list is a “delivered” system that requires very little  
programming, virtually no engineering, and is simple to install,  
operate, and service  
auto-configuring saves hours over having to locate and match  
terminal units in the field to the software in the main controller  
a one-step balance mode saves hours over the traditional method of  
balancing a VAV system  
an integrated bypass sensor assembly that does not require running  
wires back to the central controller will reduce wiring errors in the  
Trane Sales Force  
The Trane sales force has the opportunity to sell both equipment and  
controls in one integrated package. Trane provides a complete solution.  
This one-stop shopping capability is backed by the considerable  
resources that Trane offers on all of its products.  
Selling Changeover-Bypass-VAV  
Trane’s largest competitor for selling VAV zoning systems is Trane! We  
sell more rooftops with programmable thermostats than our competitors  
do selling their VAV zoning systems. In other words, even though we  
have a formidable competitor with Carrier’s VVT system, we would and  
could hold a similar share in the marketplace by selling Trane’s VariTrac  
over single units with programmable stats without even worrying about  
our competition.  
The most effective way to sell Trane’s zoning systems against the  
competition is based on system simplicity, auto-configuration, an  
integrated system, and the new digital display. In addition, many other  
new features and functions have been added. Refer to the table on page  
6 for more information.  
Finally, we need to capitalize on our contractor relationships. In many  
areas of the country we have not begun to call on these light commercial  
contractors, or maintain the relationships that exist today. The key to  
success is to take full advantage of the delivered products that are now  
available, call on and educate your contractors, then sit back and take  
VAV zoning controls are available from a variety of sources, however,  
most of them do not offer an integrated package with the equipment.  
Many of these companies do not offer a pre-engineered package that  
comes as a standard offering. Instead they supply parts or pieces of the  
whole system. There is significant risk in working with these companies  
up-front and after installation. Coordinating mechanical and electronic  
builds between multiple suppliers is difficult and it is possible that these  
suppliers will not be able to respond to service or reliability issues.  
Trane is the leading system controls supplier on new equipment, and  
holds the leading share of the new construction controls market. Trane  
has made significant effort to become the premier integrated systems  
leader, and the competition is not even close.  
Literature Order Number  
March 2002  
An American Standard Company  
Stocking Location  
For more information contact your local district  
office or e-mail us at  
Since Trane has a policy of continuous product and product data improvement, it reserves the right to  
change design and specifications without notice.  

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