Trane 3VAV-PRC003 User Manual [EN]

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VariTrac™ Changeover Bypass VAV (Tracker System CB)

June 2004

VAV-PRC003-EN

Introduction ............................................................. 4

Comfort Made Simple ................................................................ 4

The Changeover Bypass VAV Comfort Advantage ....................... 4

VariTrac Product Enhancements ................................................. 4

Features and Benefits ........................................... 5–12

Overview ................................................................................... 6

Central Control Panel ................................................................. 7

Optional Operator Display .......................................................... 7

Communicating Bypass Controller ............................................. 8

Tracker System Integration ......................................................... 8

VariTrac Bypass Dampers ........................................................... 9

VariTrac Zone Dampers ............................................................ 10

Unit Control Module ................................................................ 10

Zone Sensors ...................................................................... 11–12

™ ® The following are trademarks or

registered trademarks of their respective

companies: Precedent, ReliaTel, Trace, Tracker,

VariTrac, VariTrane, Voyager.

Application Considerations ................................ 13–24

Introduction .............................................................................. 13

Zoning Considerations .............................................................. 13

Effective Changeover Bypass VAV System Design ................ 14–19

Pressure Dependent vs. Pressure Independent .......................... 20

Local Reheat Capabilities Using VariTrane VAV Units ............. 20–21

Bypass Damper Operation ........................................................ 22

Building Pressure Control ......................................................... 23

Application Tip Summary .......................................................... 24

Selection Procedures ......................................... 25–28

VariTrac Dampers ................................................................ 25–26

Service Model Numbers ........................................................... 27

Typical Bill of Materials ............................................................. 28

Electrical Data and Connections ......................... 29–34

Specifications ................................................... 35–38

Acoustics .......................................................... 39–40

Dimensions and Weights .................................... 41–46

Glossary ........................................................... 47–48

3VAV-PRC0 03-EN

Introduction

Comfort Made Simple

Trane has a long history of innovative leadership in variable air volume (VAV) technology. Trane introduced the:

• first fan-powered VAV unit

• first factory-commissioned DDC controller

• first preprogrammed VAV controller designed specifically for VAV applications

Trane is now the leading manufacturer of VAV terminal units and VAV-related products in the world.

The introduction of VariTrac™ in 1989 brought VAV controls expertise into the changeover bypass zoning market.

Trane is committed to continuous product improvement and now introduces a new generation of VariTrac controls. This latest generation retains the functionality of the original VariTrac system with exciting new enhancements, utilizing the best of today’s technology.

Figure 1. The VariTrac CCP maximizes system efficiency and reliability by coordinating the components of the changeover-bypass system

The Changeover Bypass VAV Comfort Advantage

Packaged unitary systems offer a popular and cost-effective method of supplying conditioned air to light commercial buildings. These systems commonly have a constant-volume fan with a fixed outside air damper and a single thermostat. While a constant volume system may meet the overall thermal requirements of the space, only a single thermostat is available. This system may be insufficient in multiplespace applications with independent thermal load requirements.

Changeover bypass systems use the practicality and cost effectiveness of constant volume unitary components like packaged rooftop units, split systems, or water-source heat pumps, and simply add dampers and a central control panel to coordinate the components. This allows up to 24 individual sensors (thermostats) for independent temperature control.

Figure 2. The VariTrac CCP with optional touch-screen interface simplifies system operation with intuitive icon-driven design

VariTrac Product Enhancements

Selected enhancements of the new VariTrac product are listed below.

• A new central control panel (CCP) with improved system temperature and pressure control functions

• An optional touch-screen operator display for the CCP with built-in time clock for easier system setup and control

• A communicating bypass controller allows duct pressure and duct temperature to communicate to the system via a twisted shielded wire pair, thus eliminating costly “home-run” wiring

• The next generation UCM zone controller allows CO sensor inputs

• A digital display zone sensor for simplified occupant control

Advanced Control Options

Some of the VariTrac intelligent system control features are listed below.

-based demand control ventilation

•CO

resets the position of the HVAC unit ventilation air damper when zone CO levels rise

• Zone-based HVAC unit control operates heating and cooling only when zone demand exists

• Discharge air control to avoid extreme supply air conditions and maximize equipment life and occupant comfort

• A simplified system-balancing process is available via PC software or the touch-screen interface

• Global zone temperature setpoint limits simplify startup, commissioning, and operator control

and occupancy

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Features and Benefits

Figure 3. VariTrac changeover-bypass VAV system components

Communicating Bypass Controller

HVAC Unit

Bypass Damper

VariTrac Central Control Panel with touchscreen interface

VariTrac Zone

Damper

VariTrac Central Control Panel (CCP)

The CCP is the system level controller which coordinates and monitors VariTrac system operation, including HVAC system supply

supply air temperature, all zone temperatures and setpoints, fan mode, economizer position (when paired with CO demand controlled ventilation), time-of-day scheduling, zone grouping logic, system override mode (after hours operation), and much more.

Rooftop

Split System

pressure and airflow, heating/cooling mode,

HVAC Unit

VariTrac changeover bypass systems operate with Trane and non-Trane products, including split systems, packaged rooftop units, and water-source heat pumps. These systems are generically referred to as HVAC (heating, ventilating, and air conditioning) units. When combined with a Trane packaged rooftop with ReliaTel™ controller, wiring, installation, and system startup efficiency is maximized by connecting with a simple twisted shielded wire pair.

Zone Sensor

Bypass Damper w/ Wire and Quick Connect

A round or rectangular damper ducted between the HVAC supply and return ducts. It

is easily connected via a “quick-connector” which provides quick and consistent field wiring. The bypass damper is modulated by the CCP to maintain required system

static pressure.

Communicating Bypass Controller

A single enclosure with duct temperature sensor,

static pressure sensor, and communicating

controller (UCM) which easily mounts on the

supply ductwork. The UCM provides power to

drive the bypass damper actuator.

Zone Sensor

Zone sensors (sometimes referred to as

thermostats) measure space temperature and

report it to the zone damper controller (UCM).

Five models are available to satisfy varied aesthetic and application preferences.

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WSHP

Features and Benefits

Overview

Changeover-bypass VAV is a comfort system developed for light commercial applications. A changeover-bypass VAV system responds to changing cooling or heating requirements by varying the quantity or volume of air delivered to each zone. Each zone has a thermostat for individual comfort control. An HVAC unit delivers a constant volume of air to the system. As the volume of air required by the zone changes, excess supply air is directed to the return duct via a bypass duct and damper. (See Figure 3 for typical system components.)

A changeover-bypass VAV system combines the comfort benefits of VAV with the cost effectiveness and simplicity of packaged, constantvolume unitary equipment.

How the System Works

A changeover-bypass VAV system commonly consists of an HVAC unit with a constant-volume supply fan, and direct-expansion (DX) cooling. This combined system has the ability to “change” to the heating mode or cooling mode, depending on individual zone comfort requirements. A heating coil or a gas-fired heater and an outside air damper are possible options.

temperature sensor in each zone

A communicates information to an electronic controller on the VAV terminal unit. The controller then modulates the zone damper open or closed, supplying heating or cooling air to the zone.

The HVAC unit delivers a constant volume of supply air to the system. In order to maintain duct static pressure, a bypass duct and damper are required to bypass (detour) air not required in the zones.

The VAV terminal unit controller communicates zone temperature information to a central control panel (CCP). The CCP also gathers information from the system, including duct static pressure and supply-air temperature. The CCP determines zone heating or cooling needs using voting (or polling) logic, then requests heating or cooling from the HVAC unit. The CCP directs the HVAC unit to provide ventilation air to high-occupancy areas (demand control ventilation) or freecooling when the outside air temperature falls below the temperature setpoint (economizer control).

Auto Changeover

“Auto changeover” refers to the ability of the system to automatically change between the heating and cooling modes.

In a changeover-bypass VAV system, the CCP determines whether the HVAC unit should heat or cool by polling the temperature of the individual zones. It then compares the zone temperatures to the space temperature setpoints. If the supply air does not meet the criteria for the heat or cool mode called for, the CCP sends a signal to the HVAC unit to change the system to the opposite mode.

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Features and Benefits

Central Control Panel

The VariTrac central control panel (CCP) serves as the central source of communications and decisionmaking between the individual zones and the HVAC unit. The CCP determines system heating and cooling modes and coordinates the system supply air temperature and static pressure to satisfy building thermal load conditions. Inputs to the CCP include 24VAC power and communication wiring to the zone dampers and bypass control.

Binary inputs consist of priority shutdown and occupied/unoccupied modes. Heating, cooling, and the HVAC unit fan on split systems and non-Trane HVAC units can be controlled through binary outputs on an accessory relay board. If a Trane rooftop air conditioner with factory-installed electronic controls is used, the CCP can control heating, cooling, and the fan with a twowire communication link tied to an interface board mounted in the rooftop. It can also display status information from the electronic controller in the rooftop. (See Figure 4.)

Figure 4. A screen representation from the central control panel illustrating system status

Figure 5. VariTrac central control panel

CCP Feature Summary

• Communicates with up to 24 VAV unit control modules (UCMs)

• Makes optimal heating and cooling decisions based on setpoint and temperature information received from individual zones

• Automatically calibrates all dampers, significantly reducing labor-intensive and costly field calibration

• Windows-based PC software simplifies setup and control

• Provides diagnostic information for all system components via the operator display or PC software

• Provides status and diagnostic information for Trane HVAC units equipped with Trane ReliaTel or UCP electronic controls

Figure 6. VariTrac central control panel with optional operator display

Optional Operator Display

The optional operator display is a backlit, liquid crystal display with touchscreen programming capability.

The operator can access system and zone status through the display and perform basic setup of zone VAV UCMs and CCP system operating parameters. The display allows an installer to commission a VariTrac system without using a PC. The operator display has a seven-day time clock for stand-alone scheduling capability.

Operator Display Feature Summary

• Backlit LCD touch-screen display for easy operator interface

• Combination of icon- and menu-based navigation provides intuitive operation

• Provides a level of control for the daily operator, and a second level for commissioning and service

• Three levels of security are available to protect system settings

• Seven-day time clock for stand-alone, time-of-day scheduling

VAV-PRC003-EN 7

Features and Benefits

Communicating Bypass Controller

The communicating bypass controller is a single control enclosure with the following integrated devices included:

• integrated UCM board

• static pressure sensor

• discharge air temperature sensor

The communicating bypass controller directly controls the bypass damper and communicates duct conditions to the central control panel via a simple twisted shielded wire pair.

Quick Connect

Minimizes field wiring labor and assures wiring consistency

Duct Temperature Sensor

The supply air temperature sensor allows the CCP to control heating and cooling stages to maintain the supply air temperature. Supply air temperature setpoints can be edited through the operator display or PC software.

Static Pressure Sensor

The static pressure sensor measures duct static pressure and positions the bypass damper(s) to maintain the static pressure setpoint.

Tracker System Integration

The VariTrac system can be fully integrated with the new family of Tracker building controls. A Tracker building management system can manage multiple VariTrac systems from a single control point.

Tracker System Summary

• Controls up to 10 VariTrac systems from a single Tracker panel for easy building operation

• LCD touch-screen operator display or Tracker PC software interface provides single-point building management by a local operator

Figure 8. Tracker System Architecture

• 365-day scheduling function and the flexibility of up to 10 schedules

• Assign all systems to a single schedule, if desired, for simplified schedule changes

• Exception scheduling feature for easy management of vacations and holidays

• Automatically adjusts for daylight savings time and leap year

• Remote communications capability via modem for system programming and control

Figure 7. Communicating bypass controller side view and 3-D view

Duct Temperature Sensor

Static Pressure Sensor

Quick Connect

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Up to 24

VariTrac or

VariTrane Dampers

Features and Benefits

VariTrac Bypass Dampers

Bypass dampers are noncommunicating VariTrac dampers and include an integrated fully-modulating 24 VAC electric actuator.

Field wiring errors are reduced with a quick-connect harness that plugs into the communicating bypass controller.

Dampers are nominally rated up to 1800–2400 fpm at 1.75" of static pressure, depending on size.

For damper performance information, see Table 2.

Round Bypass Damper Summary

• Round bypass dampers are available with inlet diameters 6, 8, 10, or 12 inches

• Heavy gage galvanized steel cylinder with rolled bend for high structural integrity and corrosive resistance

• Metal-to-metal blade seal provides tight shutoff for low leakage

• Aerodynamic blade design provides a constant torque for stable operation at high velocity

• Factory-installed, direct-coupled, fullymodulating 24 VAC actuator

• Rated up to 2400 fpm at 1.75" of static pressure

Rectangular Bypass Damper Summary

• Rectangular bypass dampers are available in sizes 14 x 12, 16 x 16, 20 x 20, and 30 x 20 inches

• Formed heavy gage galvanized steel frame, mechanically joined with linkage concealed in the side channel

• Air linkage is minimized with an opposed blade design with stainless steel side seals

• Damper casing is 16 inches long and constructed of heavy gage galvanized sheet metal with and outlet for easy installation

• Blades are six-inch nominal width, heavy gage galvanized steel

• A blade rotation stop feature prevents over-rotation of the blades in the fully open position

• Factory-installed, direct-coupled, fullymodulating 24 VAC actuator

• Rated up to 3000 fpm at 2" of static pressure

cleats on the inlet

VAV-PRC003-EN 9

Features and Benefits

VariTrac Zone Dampers

VariTrac zone dampers are fullymodulating, pressure-dependent VAV devices. The dampers control zone temperature by varying the volume of air flowing into a space. Each VariTrac damper has a control box with a VAV control board and actuator enclosed. The dampers are designed to operate in static pressures up to 1.75 in. wg.

Round Zone Damper

• Round dampers are available in 6, 8, 10, 12, 14, and 16 inch diameters

• Heavy gage galvanized steel cylinder with rolled bend for high structural integrity and corrosive resistance

• Metal-to-metal seal provides tight shutoff

• 90° blade rotation for a wide control range and stable operation

• Aerodynamic blade design provides constant torque for stable operation at high velocity

• Rated up to 2000 fpm at 1.75" of static pressure

Rectangular Zone Damper

• Rectangular dampers are available in sizes 8 x 12, 8 x 14, 8 x 16, 10 x 16, 10 x 20, and 14 x 18 inches

• Heavy gage G90 galvanized steel frame assembled by a mechanical joining process

• Single-ply, heavy gage G90 galvanized steel blades

• Linkage has high impact ABS gears, and is 3" nominal diameter

• Factory-installed 24 VAC direct-coupled actuator

• Rated up to 2400 fpm at 2" of static pressure

Unit Control Module

A unit control module (UCM) is the individual zone controller for the VariTrac air damper and is mounted on each zone damper. The unit controller continually monitors the zone temperature to maintain space temperature. The UCM varies the damper position as needed to meet zone setpoints and communicates current space requirements and system operating modes to the CCP.

The UCM can also control local heat. Local heat may be duct- or spacemounted, and can be staged electric, pulse-width modulating electric, and modulating or two-position staged hot water.

Figure 9. VariTrac rectangular and round zone dampers with UCMs

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Features and Benefits

Zone Sensors

Figure 10. DDC zone sensors Figure 11. DDC zone sensor with LCD

DDC Zone Sensor

The direct digital control (DDC) zone sensor is an uncomplicated, reliable electro-mechanical room sensor. No programming is required and most sensors contain an internal communications jack.

Models are available with combinations of features such as override (on-cancel) buttons and space-mounted setpoint.

Four sensor variations are available:

• Sensor only (no communications jack)

• Sensor with override buttons

• Sensor with temperature setpoint only

• Sensor with temperature setpoint and override buttons

DDC Zone Sensor with LCD

The DDC zone sensor with LCD (liquid crystal display or digital) is compatible with VariTrane VAV and VariTrac controllers.

Digital Zone Sensor Summary

• Displays setpoint adjustment and space temperature in °F or °C

• Simple, two-button control of space setpoint

• Setpoint control and room temperature display can be optionally disabled

• Includes button for timed override and a cancel feature for after-hours system operation

• An easily accessible communications jack is provided for Trane portable edit terminal devices

• Nonvolatile memory stores last programmed setpoints

• For field balancing, maximum and minimum airflow or position can be overridden from the sensor

VAV-PRC003-EN 11

Features and Benefits

Figure 12. Wall-mounted CO

Figure 13. Duct-mounted CO

Sensor

sensor

Wall- and duct-mounted carbon dioxide

) sensors are designed for

(CO

demand-controlled ventilation zone applications. The sensor is compatible with VariTrane VAV and VariTrac controllers. The Trane CO measure carbon dioxide in parts-per-

sensors

million (ppm) in occupied building spaces. Carbon dioxide measurements are used to identify under-ventilated building zones. Outdoor airflow increases beyond design ventilation rates if the CO

exceeds specified levels.

CO2 Zone Sensor Summary

• Use with the UCM CO2 input for demand control ventilation

Figure 14. Zone occupancy sensor

Zone Occupancy Sensor

The energy-saving zone occupancy sensor is ideal for zones having intermittent use during the occupied mode. The sensor sends a signal to the VAV controller upon detection of movement in the coverage area. The VAV system then changes the zone from occupied standby mode to occupied mode.

Occupancy Zone Sensor Summary

• Compatible with VariTrane VAV and VariTrac controllers

• Used with zone damper UCM for controlling the occupied standby function

• Ceiling-mount PIR occupancy sensor detects motion over an adjustable range up to 360 degrees

• Single detector covers up to 1200 square feet. For areas larger than 1200 square feet, multiple sensors can be wired in parallel

• Adjustable time delay avoids nuisance change of state on loss of detection

• Adjustable sensitivity

• SPDT isolated contacts connect to UCM input

Figure 15. Auxiliary temperature sensor

Auxiliary Temperature Sensor

The auxiliary temperature sensor is used with any UCM damper control. The sensor allows the operator to monitor duct temperature or air temperature leaving a reheat device at the zone damper. This sensor is used for automatic changeover of a UCM damper when not using a CCP. The auxiliary temperature sensor is ideal for remote monitoring and diagnostics from the CCP operator display.

Auxiliary Temperature Sensor Summary

• Thermistor sensing element 10,000 Ohms @ 77°F

• Wiring connection 8 feet, 18 awg

• Sleeving for wire leads is acrylic #5 awg grade C rated @ 155C

• Silicone-based NDIR sensor technology for long-term stability

• Measurement range of 2000 ppm CO input with an output of 0–10 Vdc

• Wall-mount transmitter is compact and aesthetic in appearance

• Optional zone return duct-mount transmitter is available

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Application Considerations

Introduction

The VariTrac system is a changeoverbypass VAV system. One fan supplies either warm air for heating or cool air for cooling. It is typically applied in small buildings which use unitary heating/cooling air conditioners. These buildings need the simplicity and low cost of unitary equipment, but more than one comfort control zone (one zone temperature sensor) for each air conditioner.

When is VariTrac a good HVAC system choice? To help answer this question, several important application concepts and considerations are discussed below.

Figure 16. System design affects occupancy comfort

Least

Energy Savings • Comfort • Flexibility

Most

Single Zone Building

One thermal and one comfort zone

Thermal Zoned Building

Multiple thermal zones

each with one

comfort zone

Thermal and

Comfort Zoned Building

Multiple thermal zones

each with multiple

comfort zones

Zoning Considerations

Consider the following two questions when evaluating your HVAC system design:

Will the building occupants be comfortable?

with a single-zone HVAC unit and one zone sensor provides comfort to occupants near the zone sensor. However, occupants in perimeter areas or interior rooms may be too hot or too cold.

Will comfort be consistent from room to room and area by area?

building is normally divided into thermal zones for increased comfort control and energy savings. Each thermal zone should have a dedicated HVAC unit. For optimum comfort, each thermal zone should be further divided into comfort zones.

Choosing the number and location of thermal and comfort zones is critical in planning an effective system. Some things to consider in the design process include:

• Geographic location

• Orientation of the building to the sun

• Prevailing winds

• Wall construction (glass, insulation, building materials)

• Building layout, design, occupancy and occupancy pattern throughout the day and year

• Activities in each zone

A system designed

Zoned unitary systems, such as changeover-bypass VAV, di vide thermal zones into smaller comfort zones. Each comfort zone has a damper and zone sensor that controls the amount of heated or cooled air delivered to the zone. A central system controller monitors the status of each zone damper and zone sensor. The controller then makes the decision to heat or cool for the HVAC unit.

Individual comfort zones served by a common HVAC unit (part of the same thermal zone) can require heating and cooling at the same time. In a

changeover-bypass VAV system, the unit alternately provides warm and cool air in an attempt to satisfy the needs of all comfort zones. This is effective if the simultaneous calls for heating and cooling exist for short time periods only. Wide temperature variations may occur if some comfort zones need heating for extended periods of time while others need cooling.

Some comfort zones require special consideration because of their use or location. An example is the foyer or reception area of an office building. These areas often have wide variations in thermal load because of glass (relative to other areas of the building) and frequently-opened exterior doors. Another example is an interior storage room with the need for ventilation but little or no heating or cooling. These zones can significantly influence efficient operation and comfort levels throughout the building.

Preferably, areas such as these are designed as separate thermal zones with dedicated HVAC units. However, this may be impractical or costly. Instead, use fan-powered variablevolume terminal units, or units with local reheat.

VAV-PRC003-EN 13

Application Considerations

Figure 17. Design process steps

Step 1. Define Occupant

Comfort Needs

Involves architect,

engineer(s), and building owner

Step 2. Define Thermal Zones

Involves engineers

and contractors

Step 3. Determine

Comfort Zones

Involves engineers,

contractors, and building owner

Step 4. Size Heating/

Cooling Equipment

Involves engineer(s) and contractors

Step 5. Size Zone and

Bypass Damper Units

Involves engineer(s) and contractors

Step 6. Design the Duct system

Involves engineer(s) and contractors

Step 7. Air Diffuser

Selection and Placement

Involves engineer(s) and contractors

Effective Changeover Bypass VAV System Design

Unitary zoning systems feature low first cost and quick, easy system design and equipment selection. The system is simple, but it is essential that key elements are considered during the design process.

This section offers a system design sequence and discusses application considerations that, when followed, help avoid system control and operational instabilities.

Suggested design steps for unitary zoning systems are summarized in Figure 17.

Step 1. Define occupant comfort needs

The design process begins by considering the needs of building occupants and intended building use.

y What is the intended use of the

building? Is the building usage primarily office space? Is there a manufacturing operation? Are there areas that have special requirements such as computer or electronic rooms, video/television production, training facilities, etc.?

y What physical activity level is

expected of the occupants? Seated occupants require different indoor temperatures for comfort than continuously moving occupants. An example may be a building with a mix of office space and light assembly or manufacturing.

y Where will the occupants be

located and at what times? Pay particular attention to areas with intermittent use, such as conference, training, and lunchrooms.

y How are the occupants expected

to dress? Give consideration to how the building occupants will dress. Will they dress in traditional business attire, such as long-sleeved shirts or blouses, ties, and jackets? Or, will they dress in

cooler, casual attire, such as golf shirts, light slacks, skirts, or shorts?

Gather as much usage information as possible before designing a system. This can be challenging, particularly when finishing out tenant spaces. However, usage information is crucial to the selection of heating and cooling equipment, building zoning, and duct layout.

Several publications provide guidance for properly assessing indoor space comfort. An example is ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) Standard 55, Thermal Environmental Conditions for Human Occupancy. This standard specifies the combinations of indoor space environments and personal factors (activity and clothing) that will produce thermal environmental conditions acceptable to 80 percent or more of the occupants within a space. Standard 55 addresses temperature, thermal radiation, humidity, and air speed.

ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality, is another source for occupant comfort and safety issues regarding indoor air quality. The standard recommends that relative humidity be maintained between 30 and 60 percent. This maximizes comfort and reduces the potential for microbial growth.

Step 2. Define the Thermal Zones

A thermal zone is an area with similar load profiles and occupant comfort requirements. A thermal zone can be a single room, an area, a group of rooms or an entire building. Defining the thermal zones within a building is crucial to designing a comfortable indoor environment. Each thermal zone is conditioned by a single heating and/ or cooling unit. The load of the thermal zone determines the size of the heating and cooling unit.

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Application Considerations

Cost vs. Comfort

First cost can be reduced by limiting the number of thermal zones. Unfortunately, this may impact the thermal flexibility of the system, and result in zone comfort issues. Let’s take a closer look at this important system decision known as “thermal zoning.”

Characteristics of a building which can influence thermal load are:

• Orientation of the building (North, South, East, West)

• Amount and thermal resistance (Rvalue) of glass (walls, skylights, etc.)

• Expected occupancy within the area

• Interior partitions and doors

• Varying loads from equipment or processes

Let’s examine a few building examples and discuss the zoning criteria of each.

Figure 18.

Building Example 1

Men's Restroom

Women's Restroom

illustrates a small, poorly insulated office on the left, and improved design on the right.

Building Example 1

(See Figure 18.)

Consider an existing single-story office building which is small, poorly insulated, with many large windows and few interior partitions. On a clear, cool spring day, the entire building is cool in the morning so heating is required. By afternoon, however, the south side of the building being influenced by the solar load, is warm and requires cooling. The north side remains shaded and continues to require heating. This situation results in a simultaneous requirement for heating and cooling for extended periods. Due to the varying loads throughout the building, controlling the building as a single thermal zone (with a single HVAC unit) cannot satisfy the comfort needs

Men's Restroom

of all areas. It also is not a good candidate for a zoning system because of the simultaneous need for heating and cooling.

A similar building with good insulation and fewer shaded windows, on the other hand, may be a good candidate for a single thermal zone with individual comfort zones. The reduction in wall glass reduces the solar effect on the building resulting in all areas of the building having similar load profiles throughout the day. In this case, the building has a single thermal zone and is a good candidate for one HVAC unit. Individual comfort zones (zone dampers) will be needed to assure comfortable conditions throughout the zone.

Women's Restroom

Thermostat

Poor Design Elements

• One thermostat for space

• Glass windows with no shading

• Minimal wall insulation

Glass windows

with no shading

VAV-PRC003-EN 15

Minimal wall

insulation

ThermostatT

Shaded

Windows

ThermostatT

Improved Design Elements

• Multiple zone thermostats

• Shaded windows

• Insulated walls

Insulated

Walls

ThermostatT

Application Considerations

Building Example 2

(See Figure 19.)

Consider a strip mall in the spring or fall with stores that face both east and west. In the morning, the east side of the building gets full sun and warms up while the west side is shaded and requires heating. In the afternoon, the east side of the building may need heat and the west side cooling. Because of the thermal load variation throughout the day, this building will not remain comfortable if designed with a single heating and cooling unit.

On the other hand, comfort in this building could be improved by dividing the building into two thermal zones (two HVAC units), one serving the east exposure and the other serving the west. Even with the two systems, individual occupant comfort is not necessarily assured. Interior partitioning, varying schedules and number of occupants within the thermal zone will drive differing amounts of heating and cooling. The issues related to comfort zoning are addressed in the next section.

Outside

Doors

Jewelry

Store

Pharmacy

Figure 19.

Poor Design Elements

• One thermostat for entire space

• One HVAC unit

Clothing

Store

Building Example 2

Coffee

Shop

Electronics

Store

Toy

Store

illustrates a poorly insulated store design (above) and an improved design (below)

Outside

Doors

Jewelry

Store

Coffee

Shop

Step 3. Define the Comfort Zones

A primary criteria for defining a thermal zone is that it will not require simultaneous heating and cooling. An HVAC unit with one fan is limited to supplying either heating or cooling. Most applications with larger thermal zones however will have varying thermal needs throughout the zone. These small variations can easily be addressed by properly defining comfort zones.

A comfort zone is an area within a thermal zone that is controlled by a zone damper. The amount of conditioned (heated or cooled) air entering the space varies. This is in response to a space thermostat. ASHRAE Standard 55 recommends limiting indoor temperature variations. Temperature variations of less than 2°F in 15 minutes or 4°F in an hour. Deviations from this recommendation will cause discomfort in 80 percent of the occupants. Zoning systems can greatly reduce temperature variations caused by shifting occupancy and solar load conditions in large thermal zones.

Improved Design Elements

• Two ther mal zones

• Two HVAC units

Electronics

Pharmacy

Clothing

Store

16 VAV-PRC003-EN

Store

Toy

Store

Application Considerations

Figure 20. Diversity example

Building Perimeter

Step 4. Sizing HVAC Equipment

Once the building heating and cooling loads are known and the thermal zones have been determined, the heating and cooling equipment can be selected. Each thermal zone requires a separate heating and cooling unit. As discussed earlier, unitary zoning systems typically use packaged DX rooftop units or DX split systems. These systems are offered as heating and cooling units or heat pumps.

When selecting the heating and cooling unit for a thermal zone, load diversity within the zone should be considered to minimize equipment size and therefore reduce system first cost and operating expense. Load diversity is defined as the ratio of the instantaneous peak loads (block load) to the sum of the peak loads within the thermal zone. In recognizing load diversity, the designer acknowledges that all areas of the thermal zone will not require maximum cooling or heating at the same time.

While using diversity may reduce the size of the HVAC unit, the zone ductwork, dampers, and diffusers must be sized for the individual zone peak loads. The main trunk duct may be sized based on the HVAC unit airflow.

Wedge Zone

Calculating thermal zone diversity:

1. Determine the instantaneous peak (or block) load for the thermal zone. This information is output from load analysis software such as Trane

TRACE

2. Calculate the sum of the peak loads for each of the comfort zones within the thermal zone.

3. The diversity factor is then calculated by dividing the instantaneous peak load value by the sum of the peak loads.

The heating and cooling equipment will never be called upon to provide more capacity than was determined by the instantaneous peak load value. Consequently, the equipment capacity can be reduced by the diversity factor.

Table 1. Diversity example

Zone Time Peak Load

Interior 3 p.m. in mid-July 7.5 tons North 5 p.m. in mid-July 3.0 tons East 9 a.m. in June 2.5 tons South 4 p.m. in November 4.0 tons West 5 p.m. in September 2.5 tons

Note: The sum of blocks loads = 17.5 tons and occurs at 5 p.m. in mid-July.

or manually calculated.

Diversity

Factor

Sum of Peak Loads 19.5 tons

Instantaneous

Peak Load

Sum of Peaks

Diversity = 17.5 = 90%

North Zone

Glass

Windows

VAV-PRC003-EN 17

West Zone

Interior Zone

South Zone

East Zone

______

19.5

Application Considerations

Step 5. Size Zone and Bypass Damper Units

Sizing zone damper is relatively straightforward. The volume of airflow (in cfm or L/s) for each comfort zone should be known from the load analysis. The designer must select the duct velocity to be used for the system. Recommended zone damper velocities are 1000 to 1600 feet per minute (fpm) when applied at the branch level. Sizing dampers in this range will minimize damper cost, reduce the risk of excessive noise, and ensure adequate zone modulation/temperature control.

Figure 21. Hand balancing dampers

Dampers located immediately adjacent to the zone or diffuser may need to be sized at a lower velocity to avoid sound and airflow delivery issues.

Bypass dampers are typically sized for 80 percent of HVAC unit airflow. Recommended velocities are 1600 to 2000 fpm. Bypass dampers should be located as close to the HVAC unit as possible. (See Bypass Damper Operation for additional details.)

Note: VariTrac systems are designed for HVAC unit static pressures up to

1.75" w.c.

Hand

Balancing

Damper

Var iTrac Damper

Step 6. Designing the Duct System

Low pressure, low velocity air distribution systems, such as zoned unitary systems, are usually designed using the equal friction method. Although static regain is the duct design method of choice for medium and high velocity variable air volume systems, the added complexity is difficult to justify with smaller unitary systems. In addition, the low operating velocity of most unitary systems makes the pressure available to “regain”, small and inconsequential.

With the equal friction method, ducts are sized for a constant pressure loss per given length of duct and fitting(s). Where low noise levels are especially critical, the system velocity can be reduced by enlarging the entering and leaving ductwork, damper unit or adding duct liner. A characteristic of the equal friction method that must be considered however, is that there is no natural provision for equalizing pressure drops in the branch sections. This results in each branch duct, and thus the damper units, having different entering static pressure and airflow characteristics.

A robust system and zone unit controller, like the Trane VariTrac system, will compensate for system static changes. The use of manual (or hand) balancing dampers in the branches will also ensure that airflow is appropriately distributed to each diffuser. (See Figure 21.) The overall effect is improved acoustical and system performance.

Supply

Duct

18 VAV-PRC003-EN

Application Considerations

Step 7. Air Diffuser Selection and Placement

Supply Diffusers

Many types of supply air diffusers are used in variable air volume systems. Performance, and ultimately space comfort, can vary greatly depending on the diffuser selected. Although constant-volume diffusers will provide air to the space at full cfm, as air volume delivered to the space decreases, so does performance. Linear slot diffusers are recommended for most VAV systems.

Linear supply air slot diffusers are designed to properly mix variable air delivery of both heated and cooled air. Linear slot diffusers supply conditioned air which “hugs” the ceiling rather than “dumps” air downward on the occupants. This airflow characteristic is known as the “coanda effect”. The throw and aspiration characteristics of slot diffusers help to evenly distribute the air throughout the room or space.

Locate linear slot diffusers in the center of the room with the discharge air pattern perpendicular to a perimeter wall. To maximize diffuser performance, placement in which air discharge patterns converge at right angles should be avoided. (See Diffuser section of the VariTrane catalog (VAVPRC008-EN) for additional diffuser placement and performance recommendations.)

The throw characteristics of diffusers is well-documented. Slot diffusers should be positioned so that the velocity of the air striking an obstruction (such as a wall or column) is 75 feet per minute (fpm) or less. If airstreams from two diffusers collide, the collision velocity should not exceed 150 fpm. Higher collision velocities result in uncomfortable drafts in the lower levels of the room.

In heating applications, linear slot diffusers must be placed to offset heat loss and prevent downdraft problems along perimeter walls. The following techniques have been proven by test and experience:

• When the average glass plus wall heat loss is less than 250 Btuh/linear foot, the slot diffuser may be located in the center of the room with one or more slots blowing toward the perimeter wall.

• With glass and wall heat loss between 250 and 450 Btuh/linear foot, diffusers should be positioned to blow toward the window and the perimeter wall with a collision velocity of 75 to 150 fpm. If using a continuous glass design, position diffusers every four feet.

• If heat loss exceeds 450 Btuh/linear foot, radiation or floor mounted heated air will be required to offset the high wall heat loss.

Figure 22. Proper return diffuser orientation

Return Diffusers

Slot-style return diffusers offer some acoustical advantages over perforated grille styles. Perforated drop-in grilles typically offer little attenuation effect and thus allow sound in the plenum to break out into the occupied space. This is a problem in areas near the unitary heating and cooling unit. Improved ceiling aesthetics is also an advantage of slot return diffusers in jobs where slot supply diffusers are used. Within the occupied space, they blend with the slot supply diffusers.

A general rule of thumb is for the return air openings to equal the total area of the supply openings. If the ceiling is not tight, such as a drop-in ceiling, the return openings can be reduced by up to 50% of the supply air openings.

To promote good air distribution, return diffusers should be positioned to minimize supply air short-circuiting to the return slot. The returns should be either perpendicular to the supply airflow or parallel and offset from the supply diffusers.

VAV-PRC003-EN 19

Application Considerations

Pressure Dependent vs. Pressure Independent

Pressure-Dependent

A pressure-dependent VAV control sequence uses the space temperature sensor to directly control the position of the zone damper. The actual airflow delivered to the space is a by-product of this damper position and the static pressure in the duct upstream of the zone damper.

Ventilation air is a fixed-damper position and must be measured and set during the commissioning process.

Pressure-Independent

A pressure-independent VAV control scheme directly controls the actual volume of primary air that flows to the space. An airflow-measuring device in the VAV terminal unit makes this possible. The position of the modulating device is not directly controlled and is a by-product of regulating the airflow through the unit. Because the airflow delivered to the space is directly controlled, it is independent of inlet static pressure.

Local Reheat Capabilities Using VariTrane VAV Units

VariTrane pressure independent VAV units are a simple way to upgrade the zone VAV capabilities on a VariTrac system. The main advantage is the ability to integrate units with either hot water or electric reheat. Here are application examples where VAV units may enhance your design:

Example 1

Series fan-powered VAV units

work well in conference rooms and training rooms. Series fan-powered units supply constant air volume to the space. This provides excellent air movement in the space regardless of the internal load requirements. Hot water or electric heat are integral to the unit and optionally available to temper the air at partial load conditions.

Figure 24. Series fan-powered VAV terminal unit

Example 2

Parallel fan powered units with local heat applied help solve

problems in difficult areas to control like lobbies and vestibules. The parallel fan provides local heat to an individual zone without relying on the main HVAC unit’s heat or supply fan. This allows greater flexibility for mixing zones on a VariTrac system.

VariTrane units with integral electric or hot water heat are available as:

• single-duct

• parallel fan-powered

• series fan-powered

Figure 25. Parallel fan-powered VAV terminal unit

Figure 23. Single-duct VAV unit is available with integral electric or hot water heat

20 VAV-PRC003-EN

Application Considerations

Local Reheat Capabilities Non-VAV Options

The Trane VariTrac Zone Controller has built-in capabilities and logic to control a number of reheat sources. The previous page discussed how a VariTrane VAV unit with reheat can solve application issues by providing local reheat.

Local Reheat

Let’s investigate a few other alternatives which will provide local reheat, and result in exceptional zone temperature control.

Local reheat is particularly important when an HVAC unit is in cooling mode. Cold air is delivered to all zones whether it is needed or not. Setting the minimum cooling position to zero may not be practical based on ventilation and/or general airflow requirements. In this case, local reheat options which can be controlled by the standard VariTrac zone controller include:

• hydronic wall fin or convector unit with either modulating or two position control. (See trane.com for a full line of wall fin and convector products.)

• electric wall fin with multi-stage control

• duct-mounted electric heater with multi-stage control

• duct-mounted hot water coil with either modulating or two-position control. (See trane.com for a full line of ductmounted water coils.)

Figure 26. Trane hydronic wall fin

This is ideal for spaces with large windows or perimeter heat losses which exceed 450 Btuh per linear foot. Trane wallfin is available with various grilles and paint options and can be pedestal or wall-mounted

Figure 27. Trane electric wall fin

VAV-PRC003-EN 21

Application

eturn

Heating and

Static Pressure

Considerations

Bypass Damper Operation

When zone dampers modulate airflow to the spaces, static pressure changes in the supply duct system. High pressure in a duct system creates excessive noise and causes poor comfort control. Low pressure results in insufficient airflow to the spaces.

The HVAC unit in a changeover bypass system is constant volume and does not modulate supply airflow. Changeover-bypass VAV systems support variable-air-volume operation in the zones by using a bypass duct with a motorized damper and a pressure-sensing device.

As duct pressure rises above the static pressure setpoint, the bypass damper begins to open. Conversely, when static pressure falls below the static pressure setpoint, the bypass damper begins to close until the static pressure setpoint is reached. The optimal static pressure setpoint is automatically determined

Proper operation requires consideration of all aspects of bypass design and location. The bypass dampers and ductwork should be sized and located according to the following general recommendations:

y Avoid turbulence by locating the

bypass two to three equivalent duct diameters downstream of the HVAC unit discharge.

y Locate the static pressure and supply

air sensors in the main supply duct upstream of the bypass.

y Locate the bypass before the zone

dampers (as close to the HVAC unit as possible) to avoid comfort or noise issues.

y Size the bypass damper to maintain the

minimum required airflow through the HVAC unit (usually 80 percent of the total design cfm)

y Provide adequate access for servicing

the damper.

upon system calibration.

Figure 28. Changeover bypass variable-air-volume system

Roofto Micro Contro

and Suppl Te mperature Sensor

Supply Air Duct

22 VAV-PRC003-EN

Bypass Damper

Ductwork

Return Air Duct

R Air Duct

Application Considerations

Building Pressure Control

Comfortable, efficient building operation requires that the air pressure inside the building be slightly higher than the atmospheric pressure outside of the building. That is, the building is at a “positive” pressure with respect to the outside environment. If the indoor pressure is too low (negative), the doors may be hard to open and cold air may leak in through construction cracks, causing drafts and cold floors. On the other hand, if the indoor pressure is too high, the doors may stand open and the supply air flow to the zones may decrease, decreasing comfort.

Fixed Outside Air Dampers

Achieving appropriate building pressure is simple in a system with a constant volume supply fan and fixed outdoor air damper. To maintain a slightly positive building pressure, size the exhaust fans to remove slightly less air than is introduced through the outdoor air damper.

Outside Economizer or DemandControlled Ventilation Systems

If the system resets the quantity of outdoor air in response to occupancy demands (demand-controlled ventilation), or uses an outdoor air economizer, undesirable changes in building pressure may result. As the quantity of outdoor air intake varies, the system must exhaust a similar quantity of air to avoid over or under pressurizing the building.

When using an economizer in a changeover-bypass VAV system under low cooling load conditions (reduced airflow to the zones), the bypass damper opens to maintain the static pressure setpoint and airflow through the supply fan. As the outside air damper opens to provide economizer cooling, the return air damper closes. In buildings with a ceiling plenum return, the bypass air dumps into the ceiling plenum since it can no longer return to the fan. The plenum pressure rises and plenum air enters the zones through the return air grilles.

In buildings that have a ducted return to the fan, bypass air pressurizes the return air duct. As the return air duct pressure rises, the air flows out of the building through the barometric relief damper in the rooftop unit. Excess bypass air flows into the zones through the return air grilles.

Using the following suggestions will help maintain building pressurization control:

• Use an exhaust fan with a modulated exhaust damper to remove air from the return air plenum or duct. Energize the exhaust fan as the outside air damper opens beyond the minimum position. Sense building static and maintain building air pressure at a slightly positive level by modulating the exhaust damper position.

Figure 29. Changeover bypass with an economizer. Without proper building pressurization, bypass air may be forced out of the return duct.

Economizer

Outdoor

Air Damper

Return

Damper

Return

Opening

• Use an exhaust fan with no exhaust damper. Energize the exhaust fan when the outdoor air damper opens beyond 25 percent to remove excess outside air from the building. This method is used with some rooftop units and is effective, affordable, and easy to install.

• Use a back draft damper to prevent airflow to the return air plenum or grilles. When bypass airflow pressurizes the return duct, the back draft damper closes. Pressure in the HVAC unit return air inlet rises, causing the rooftop barometric relief damper to open. This method is less effective because the rooftop barometric relief damper is sized for a portion of the total airflow, not 100 percent of airflow which may be seen in economizer mode. As the economizer drives to the maximum position, the building usually becomes over-pressurized.

Fan

Bypass

VAV-PRC003-EN 23

Application Tip Summary

Application Considerations

Tip 1. Use comfort zones

Units serving thermal zones can provide greater comfort by dividing the thermal zones into “comfort zones” using a changeover-bypass-VAV system.

Tip 2. Create thermal zones

Create thermal zones which minimize simultaneous heating and cooling requirements. This will avoid unnecessary changeover of the system and maximize comfort. As an example, a computer room would be a poor candidate for one comfort zone of a changeover-bypass-VAV system because it will rarely, if ever, require heating.

Tip 3. Use local heat

Zones which vary thermally by requiring more heat than the other zones or require heat when the HVAC unit is in cooling mode should use local heat. Local heat in the form of VariTrane VAV units with electric or hot water heat, or wallfin, or convectors, or ductmounted coils. The standard VariTrac controller is capable of controlling the heat based on zone temperature demands.

Tip 4. Place dampers properly

The bypass damper should be ducted between the supply and the return of the unit as close to the unit as possible, and should be sized to handle 80% of the total system CFM.

Tip 5. Control building pressure

It may be necessary to provide a modulating means to control building pressure, especially when economizers or demand-controlled ventilation are used in conjunction with a changeoverbypass-VAV system.

Tip 6. Use fan-powered VAV boxes

Consider using fan-powered VAV boxes to provide local heat or to enhance comfort levels in some of your zones. Conference rooms, or zones with high wall heat loss are ideal for either series or parallel units.

24 VAV-PRC003-EN

Selection Procedures

VariTrac Dampers

VariTrac dampers are typically installed on VariTrac changeover bypass variable air volume (VAV) systems. VariTrac is ideal when applied to buildings which use unitary HVAC units. The damper units have controls, which vary air volume and maintain appropriate duct static pressure in the system to make sure that all zones receive the right amount of airflow.

Trane offers four VariTrac dampers:

• Round zone dampers with DDC controls

• Rectangular zone dampers with DDC controls

• Round bypass dampers

• Rectangular bypass dampers

Figure 30. Round and rectangular zone and bypass dampers

Zone Damper Selection Procedures

Refer to the sizing chart in Table 2 for zone dampers. Follow down the first column in the table for the desired velocity. Then follow across for the cfm (air volume) of a given VariTrac damper based on that velocity.

Note: If the cfm exceeds the damper range, increase the damper size.

Minimum airflow damper position should be set to10 percent in heating or cooling when a zone duct temperature sensor is used for stand-alone control. In addition, when controlling ductmounted electric reheat coils, cooling minimum airflow should meet the heating unit manufacturer’s guidelines. (See Application Considerations, Maximum System Effectiveness for more details.)

Bypass Damper Selection Procedures

To determine the cfm capacity required for a bypass damper, calculate 80 percent of the cfm capacity of the heating/cooling unit.

Example: If the rooftop capacity is 1200 cfm, the bypass damper should be sized for 1200 x .8 = 960 cfm.

To determine the size of the damper, locate the recommended velocity and cfm for the bypass damper.

Since a 10" round bypass damper at 1800 fpm provides 980 cfm, a 10" damper at 960 cfm would be slightly less than 1800 fpm, but still within the 1600 to 2000 fpm recommended velocity. A 10" bypass damper is selected.

VAV-PRC003-EN 25

Table 2. Damper sizing charts

Selection Procedures

Round Zone Damper

Capacity (cfm), Dimensions, and Weights

Size 6" 8" 10" 12" 14" 16"

600 120 210 330 470 640 840

800 160 280 435 630 855 1115

1000 200 350 545 785 1070 1395

1200 235 420 655 940 1280 1675

Velocity (fpm)

140 0 275 490 765 1100 150 0 1955

1600 315 560 875 1255 1710 2235

Length 12" 12" 16" 16" 20" 20"

Ship Wt 11 lbs 12 lbs 17 lbs 18 lbs 27 lbs 31 lbs

Rectangular Zone Damper

Capacity (cfm), Dimensions, Blades, and Weights

Size 8 x 12 8 x 14 8 x 16 10 x 16 10 x 20 14 x 18

600 398 464 531 663 829 1045

800 531 619 707 884 1105 1393

1000 663 774 884 1105 1382 1741

1200 796 928 1061 1326 1658 2089

Velocity (fpm)

1400 928 1083 1238 1547 1934 2437

1600 1061 1238 1415 1769 2211 2785

Blades 2 2 2 3 3 4

Ship Wt 8 lbs 10 lbs 12 lbs 14 lbs 16 lbs 18 lbs

Round Bypass Damper

Capacity (cfm), Dimensions, Blades, and Weights

Size 6" 8" 10" 12"

600 120 210 330 470

Recommended

800 160 280 435 630

1000 200 350 545 785

1200 235 420 655 940

1400 275 490 765 1100

1600 315 560 875 1255

Velocity (fpm)

1800 350 630 980 1415

200 0 390 700 1090 1570

Length 12" 12" 16" 16"

Ship Wt 11 lbs 12 lbs 17 lbs 18 lbs

Rectangular Bypass Damper

Capacity (cfm), Dimensions, Blades, and Weights

Size 14 x 12 16 x 16 20 x 20 30 x 20

600 696 1061 1658 2487

Recommended

800 928 1415 2211 3316

1000 1161 1769 2763 4145

1200 1393 2122 3316 4974

1400 1625 2476 3869 5803

1600 1857 2830 4421 6632

Velocity (fpm)

1800 2089 3183 4974 7461

2000 2321 3537 5527 8290

Blades 2333

Ship Wt 16 lbs 21 lbs 29 lbs 40 lbs

Recommended

Notes:

1. Recommended velocity for zone dampers is between 1000 and 1600 fpm. Use good standard design practices (such as location of duct).

2. Recommended velocity for bypass damper is between 1600 and 2000 fpm.

26 VAV-PRC003-EN

Selection Procedures

Service Model Numbers

VADA 0 6 A 0 0 P0

1234 56 7 891011

Digits 1, 2, 3, 4 – Product Type

VADA = VariTrac Air Damper

VARA = Rectangular Air Damper

Digits 5, 6 – VariTrac Damper Size

06 = 6" Damper

08 = 8" Damper

10 = 10" Damper

12 = 12" Damper

14 = 14" Damper

16 = 16" Damper

1R = 14 x 12 bypass damper

2R = 16 x 16 bypass damper

3R = 20 x 20 bypass damper

4R = 30 x 20 bypass damper

5R = 8 x 12 zone damper

6R = 8 x 14 zone damper

7R = 8 x 16 zone damper

8R = 10 x 16 zone damper

9R = 10 x 20 zone damper

AR = 14 x 18 zone damper

Digit 7 – Controls (all factory downloaded and verified)

A = Bypass with actuator

B = Damper only control (Changeover)

C = Damper plus up to 3 stages of

Electric

D = Damper plus 1-stage Normally-

open hot water

E = Damper plus 1-stage Normally-

closed hot water

F = Not used

G = No controls (Actuator Only)

H = Not used

J = Bypass for rectangular damper

with actuator

Digits 8, 9, 10, 11

00P0 = Design sequence

VAV-PRC003-EN 27

Table 3. Typical VariTrac changeover-bypass VAV system components

Selection Procedures

Typical Bill of Materials

Device Name Function in System Number Required

Central control panel

w/optional operator display

Communicating bypass

controller

Bypass damper(s) Supply air duct volume control to maintain

VariTrac dampers Varies air volume to the space to control comfort One per comfort zone

Zone sensors Sends space temperature and setpoint

CCP power supply 24V power for the central control panel The CCP must have a dedicated 24V

Zone damper power supply(s) 24V power for the zone dampers Power supplies may be shared; each

Trane rooftop communications

interface

Optional relay board Provides 24V control of any non-communicating

Controls the HVAC system and provides local operator interface

Sends supply duct temperature and pressure to the central control panel

appropriate static pressure in the duct

information to the zone damper controller

Allows the CCP and Trane rooftop controller to communicate with each other via simple twisted shielded wire pair

HVAC unit

One per HVAC unit/VariTrac system (thermal zone)

One per VariTrac system

One or two per system as needed to bypass from supply to return airstream

One per comfort zone (DDC sensor w/ LCD requires 4 VA)

power supply

zone requires 10VA (plus the load of optional outputs)

One per controlled Trane rooftop with ReliaTel controller

One per controlled noncommunicating HVAC unit

Figure 31. Typical components in a changeover-bypass VAV system

A & J

28 VAV-PRC003-EN

ransf

UCM

Figure 32. Central control panel field wiring

Electrical Data and Connections

lta

Line v

24 Vac

Termination Boar

omm4

Legen

omm4

omm

Comm5 UCMTrack

ormer

Figure not

Termination resistor

Tw isted pair, shielded wire

per Trane specifications

Shield termination

Contact points

Earth ground

Shield ground

Splice

Comm4 link

Comm5 link

Figure Notes:

1 All customer wiring must be in accordance with national, state, and local electrical codes.

2 Trane recommends a dedicated transformer for 24 Vac power.

3 Do not apply voltage to the priority shutdown and occupancy inputs.

4 Example of Comm5 communication link wiring. See product-specific literature for Comm5 wire connection details.

VAV-PRC003-EN 29

Figure 33. Relay board wiring

TB1

Relay Board TB2

GY1Y2W1W2/0AUXNO

NOT USED

24 VAC CLASS 2 COOL UNIT

24 VAC CLASS 2 HEAT UNIT

COOL 1

COOL 2

HEAT 1

HEAT 2

SUPPLY FAN

SPARE OUTSIDE AIR

HEAT/COOL

OR ICS

2 HEAT/2COOL HEAT PUMP

REV VALVE

AUX HEAT

COMP 2

COMP 1

Electrical Data and Connections

Figure 34. Typical relay board wiring

30 VAV-PRC003-EN

Relay Board TB2

GY1Y2W1

W2/0

TB1

HVAC Unit

24V Terminal Strip

Electrical Data and Connections

Figure 35. UCM Comm Link Wiring

Var iTrac

Te r mination Board TB2

rt Po

tic

re u

Sta

Press

TB1–1

24V

TB1–2

GND

TB4–1

BIP

ACT

Assembly Address #33

J10

J11

Communication Sensor/Bypass Control

TB1–1

24V

TB1–2

GND

TB4–1

BIP

ACT

J10

J11

VOUT

D.D.C.\U.C.M.

CONTROL BOARD

SWITCH

ADDRESS

D.D.C.\U.C.M.

CONTROL BOARD

SWITCH

ADDRESS

–

PRESS

re u s

nsduce ra

Pres

GND

TB3–6

TB3–5

A/CO2

TB3–3

SET

TB3–2

GND

TB3–1

ZONE

GRNYEL

–

TB2–6

TB2–5

–

TB2–4

TB2–3

–

TB2–2

TB2–1

GND

TB3–6

TB3–5

A/CO2

TB3–3

SET

TB3–2

GND

TB3–1

ZONE

GRNYEL

–

TB2–6

TB2–5

–

TB2–4

TB2–3

–

TB2–2

TB2–1

COMM 4

–

r so

ly p p u

Sen . p

Air S

e T

131415

Splice

COMM 5

Figure Notes:

Shield must be spliced with other

communication link shields.

Shield must be cut back and taped.

Notes:

The UCM order in this drawing is for demonstration purposes only.

No specific order is required on the Comm link.

PRESS

TB3–6

GND

TB3–5

A/CO2

TB3–3

CONTROL BOARD

SWITCH

SET

TB3–2

GND

TB3–1

ZONE

GRNYEL

–

TB2–6

TB2–5

–

TB2–4

TB2–3

–

TB2–2

TB2–1

3 through 24

To Zone Dampers

Legend

Twisted pair, shielded wire

per Trane specifications

Shielded ground

Figure note

TB1–1

24V

TB1–2

GND

TB4–1

BIP

ACT

D.D.C.\U.C.M.

Zone UCM Address #2 Zone UCM Address #1

J10

J11

ADDRESS

VAV-PRC003-EN 31

Electrical Data

and Connections

Figure 36. Communicating bypass controller wiring

CW CCW OPEN COM

ACTUATOR

HOT

ACTUATOR

TO NEC CLASS 2

24V TRANSFORMER

LOAD 8 VA

(WITHOUT ACTUATOR)

{

SPARE

CONNECTOR

J10

TB2–3

OUT

D.D.C.\U.C.M.

CONTROL BOARD

–

TB2–5

TB2–4

OUT

J11

ADDRESS

SWITCH

––

TB2–2

TB2–1

{

SHIELDED

TWISTED PAIR

COMMUNICATIONS

WIRING

TB2–6

W–HOT

BK–OPEN

R–CLOSE

BIP

ACT

YEL GRN

TB4–1

24VGND

TB1–1

TB1–2

TB2–6

TB3–2

TB3–3

TB3–1

A/CO2SETGNDZONE

AIR SUPPLY TEMP SENSOR

COMMUNICATING SENSOR/BYPASS

TB3–5

TB3–6

GND

24VAC

CONTROL BOX

PRESSURE

HIGH

PRESS

PRESSURE

TRANSDUCER

STATIC

PORT

VOUT

–

FEMALE PLUG END

OF BYPASS SENSOR

ASSEMBLY CABLE

MALE PLUG END

LOCATED ON DDC\UCM

CONTROL BOARD

D.D.C.\U.C.M.

CONTROL BOARD

ACT

32 VAV-PRC003-EN

Figure 37. UCM Wiring

OPTIONAL FIELD INSTALLED

AUX TEMP SENSOR

OPTIONAL FIELD INSTALLED

CO2 SENSOR

OPTIONAL FIELD INSTALLED

OFF WATER VALVE

OPTIONAL FIELD INSTALLED

PROPORTIONAL WATER VALVE

OPTIONAL FIELD INSTALLED

OCCUPANCY SENSOR

OPTIONAL FIELD INSTALLED

ELECTRIC HEATER

R (HOT)

O (COMMON)

GR (NC CONTACT) BK (RETURN)

OPTIONAL FIELD INSTALLED

OCCUPANCY SENSOR

TO J11

TO J10

TO J9

TO J8

OPTIONAL FIELD INSTALLED

TO J8

TO J9

TO J10

OPTIONAL FIELD INSTALLED

PROPORTIONAL WATER VALVE

TO J9

TO J8

OPTIONAL FIELD INSTALLED

ONON–OFF WATER VALVE

CO2

SENSOR

OPTIONAL FIELD INSTALLED

TB3–5

(TB1–1) 24VAC

(TB4–1) BIP (TB1–1) 24VAC (TB1–2) GND

NOT CONNECTED

3RD STG.

2ND STG. 1ST STG.

HOT

ELECTRIC HEATER

W (HOT)

BK (CLOSE)

R (OPEN)

WALL

DUCT

MOUNTED

(TB1–1) 24V

24V

(TB3–6) GND

GND

(TB3–5) A/CO2

OUT

CO2 SENSOR

OPTIONAL FIELD INSTALLED

AUX TEMP SENSOR

HEATER STAGE CONTACTOR(S)

24 VAC, 12 VA

MAX/COIL

PROP. WATER

VALV

24VAC

12 VA MAX

ON–OFF

WATER VALVE

24VAC

12 VA MAX

TB3–6

Electrical Data and Connections

24 VAC 60 HZ

NEC CLASS–2

CONTROL CIRCUIT

}

G W

}

DAMPER

ACTUATOR

WIRING

J11

J10

ADDRESS

SWITCH

–

TB2–1

TB2–2

TB2–3

OUT

SHIELDED

TWISTED PAIR

COMMUNICATIONS

WIRING

NOTES:

2. ¼" quick connect required for all field connection.

3. Zone sensor terminals 4 and 5 require shielded twisted pair wiring for communications jack equipped zone sensor options

ACT

J7J8J9

D.D.C. \ U.CM.

CONTROL BOARD

–

YEL

TB2–4

TB2–5

TB2–6

OUT

}

Factory Wiring Field Wiring Optional or Alternate Wiring

TB4–1

GRN

TB3–1

TB1–2

TB3–3

TB3–2

SETGNDZONE

24VGNDBIP

TB1–1

TB3–6

TB3–5

A/CO2

GND

CONTROL BOARD

PRESS

D.D.C. \ U.CM.

TB3–2

TB3–3

TB3–1

TB1–2

TB1–1

INSTALLED DIGITAL ZONE SENSOR

TB2–6

INSTALLED DIGITAL ZONE SENSOR

TB2–5

221 3 2

DIGITAL

ZONE SENSOR

OPTIONAL FIELD

TB2–5

TB3–2

TB3–3

45233.1

ZONE SENSOR

W/ COMM. JACK

REMOTE MTD.

OPTIONAL FIELD

TB2–6

TB3TB2TB1

TB3–1

4. No additional wiring required for night setback override (on/cancel).

5. The optional binary input connects between TB4–1 (BIP) and 24VAC (HOT) from transformer. The binary input can be reconfigured as an occupancy input via the communications interface.

6. As shipped, the aux input is configured as an AUX input. The AUX input can be reconfigured as a CO2 sensor input via the communications interface.

7. S terminal not to be used with this applications.

8. If unit mounted transformer is not provided, polarity from unit to unit must be maintained to prevent permanent damage to control board. If one leg of 24VAC supply is grounded, then ground leg must be connected to TB1–2.

9. Shields of communication wiring should be tied together and insulated.

VAV-PRC003-EN 33

Figure 38. DDC zone sensor with LCD

Digital Sensor

Board

Digital Sensor

Terminal Connection Chart

Sensor

UCM

TB1–1 TB1–1

TB1–2

TB2–1

TB2–2

TB2–3

TB3–1

TB3–2

TB1–2

TB3–1

TB3–2

TB3–3

TB2–5

TB2–6

Field Wire

Color Code

Signal Common

Communications

Electrical Data and Connections

TB1–1

24V

–2–2

GND

J11

J10

TB2–1

Temperature

–2

Setpoint

TB3–1

+ (High)

–2

– (Low)

–2

ADDRESS

SWITCH

TB2–1

TB2–2

CONTROL BOARD

–+–+

TB2–3

TB2–4

TB2–5

ACT

D.D.C.\U.C.M.

–

GRNYEL

TB2–6

TB4–1

TB1–2

GNDBIP

TB3–1

GNDZONE

TB1–1

24V

TB3–2

TB3–3

TB3–5

PRESS

TB3–6

GNDA/CO2SET

Optional

Field Mounted

Aux. Temp. Sensor

Figure 39. DDC zone sensor wiring

J11

J10

ADDRESS

SWITCH

CONTROL BOARD

–+–+

TB2–1

TB2–2

TB2–3

TB2–4

TB2–5

Mechanical Sensor

Terminal Connection Chart

Sensor

UCM

Field Wire

Color Code

TB1–1 TB3–1

TB1–2

TB1–4

TB1–5

TB3–2

TB2–5

TB2–6

Night Setback

Override Option

PB1

Adjustable

Setpoint Option

Comm 1

Communications

Jack

Sensor

Warm er

Cooler

Communications (Optional)

TB1–1

Temperature

–2

Signal Common

–3

Setpoint

–4

+ (High)

– (Low)

–5

34 VAV-PRC003-EN

ACT

D.D.C.\U.C.M.

–+

TB2–6

GRNYEL

TB4–1

TB1–1

TB1–2

24V

GNDBIP

PRESS

TB3–1

GNDZONE

TB3–2

TB3–3

TB3–5

TB3–6

GNDA/CO2SET

Field Mounted

Aux. Temp. Sensor

Figure Notes:

Shield must be spliced with other

communication link shields

Shield must be cut back and taped

at sensor.

Optional

Specifications

Figure 40. VariTrac DDC zone

sensors

Table 4. Zone sensor options

Zone Sensor Options Required Wires

Number of

Sensor only (no communications jack available) 2 Sensor with adjustable setpoint 3 Sensor with night setback override and cancel buttons 2 Sensor with adjustable setpoint and night setback

override and cancel buttons 3 Sensor with digital display and adjustable setpoint and

night setback override and cancel buttons 5

Notes:

Most sensors have a communication jack available as an option. If these jacks are used, they must be wired to the UCM using an approved two-conductor, shielded cable. The communication jacks do not need to be wired for the system to operate properly.

Three wires are required for sensor connections. Two wires are required for 24-Vac power connection.

VAV-PRC003-EN 35

Specifications

Figure 41. VariTrac central control

panel components

Figure 42. VariTrac UCM round damper

Table 5. VariTrac control panel specifications

Power Requirements 20–30 Vac, 60 Hz, single-phase, 30 VA minimum. Class 2 transformer

Operating Environment 32°–122°F (0°–50°C), 10–90% relative humidity, non-condensing Storage Environment -40°F–122°F (-40°–85°C), 5–95% relative humidity, non-condensing Control Enclosure NEMA 1 resin enclosure, plenum rated Mounting Mount directly on wall surface or mount on recessed 4" x 4"

Weight 2.5 lbs. (1.13 kg) Communication Link Wiring Communication link wiring must be Level 4 22-AWG twisted shielded

Binary Input Voltage (provided by VariTrac CCP): 10–14 Vdc

UL Approval The VariTrac Central Control Panel is UL approved. Memory Backup Upon a power loss, all operator-edited data stored in the VariTrac Central

required.

(101.6 mm x 101.6 mm) conduit box.

pair wire with stranded tinned copper conductors. Maximum total wire length is 3,500 ft (1066.8 m). Wire must meet Trane specifications.

Current (provided by VariTrac CCP): 10–14 mA Note: Only “dry” contacts may be attached to binary inputs.

Control Panel is maintained permanently.

Table 6. UCM damper specifications

Power Requirements 20–30 Vac, 60Hz, single-phase 10 VA minimum (plus load of optional heat

Operating Environment 32°–120°F (0°–49°C). 10–90% relative humidity, non-condensing Storage Environment -50°–20 0°F (-46°–93°C). 5–95% relative humidity, non-condensing Control Enclosure NEMA 1 metal enclosure, plenum rated Communication Link Wiring Communication link wiring must be Level 4 22-AWG twisted shielded

outputs). Class 2 transformer required.

pair wire with stranded tinned copper conductors. Maximum total wire is 3,500 ft (1066.8 m). Wire must meet Trane specifications.

36 VAV-PRC003-EN

Specifications

Figure 43. Communicating bypass

controller

Figure 44. Zone occupancy sensor

Table 7. Communicating bypass control assembly specifications

Power Requirements 20–30 Vac, 60Hz, single-phase 15 VA minimum. Class 2 transformer

required.

pair wire with stranded tinned copper conductors. Maximum total wire is 3,500 ft (1066.8 m). Wire must meet Trane specifications.

Table 8. Zone occupancy sensor specifications

Power Supply 24 Vac or 24 Vdc, ±10% Maximum VA Load 0.88 VA @ 24 Vac, 0.722 VA @ 24 Vdc Isolated Relay Rating 1 A @ 24 Vac or 24 Vdc Operating Temperature 32°–131°F (0°–55°C) Storage Temperature -22°–176°F (-30°–80°C) Humidity Range 0–95% non-condensing Effective Coverage Area 1200 sq. ft (365.8 m) Effective Coverage Radius 22 ft (6.7 m) Housing Material ABS plastic

Ideal for zones with intermittent occupancy like conference rooms). When occupied, the zone reverts to unoccupied setpoints to save energy.

VAV-PRC003-EN 37

Specifications

Figure 45. DDC zone sensor with

digital display

Figure 46. CO

duct sensor

Table 9. Digital zone sensor specifications

Thermistor Resistance Rating 10kW at 77° (25°C) Accuracy at 77°F (25°C) 0.4°F (0.2°C) Setpoint Resistance Rating 500 Ohms at 70°F (21.2°F) Display Zone Temperature Range 40°–99°F (10° to 35°C) Display Setpoint Range 50°–90°F (10° to 32°C) Operating Temperature 0°–120°F (–18° to 49°C) Storage Temperature –20°–130°F (–29° to 54°C) Humidity Range 5–95% non-condensing Power Supply 24 VAC Maximum VA Load 4 VA Housing Material Rigid vinyl

Table 10. CO2 sensor specifications

Duct Wall

Dimensions 3 1/8" × 3 1/8" × 7 3/4" 4 1/4" × 3 1/8" × 1 7/16" Operating Temperature 23°–113°F (–5°–45°C) 59°–95°F (15°–35°C) Accuracy at 77°F (25°C) < ± (30 ppm CO2 + 3% of reading) < ± (40 ppm CO2 + 3% of reading) Measuring Range 0-2000 parts per million (ppm) Recommended Calibration Interval 5 years Response Time 1 minute (0–63%) Storage Temperature –4°–158°F (–20°–70°C) Humidity Range 0 to 85% relative humidity (RH)

Figure 47. CO2 wall sensor

38 VAV-PRC003-EN

Output Signal (jumper selectable) 4-20 mA, 0-20 mA, 0-10 VDC Resolution of Analog Outputs 10 ppm CO2 Power Supply Nominal 24 VAC Power Consumption <5 VA Housing Material ABS plastic

Acoustics

Acoustics are tricky to define for specific jobsites. To provide an acoustical overview of a typical office system with mineral glass fiber dropped ceiling, ARI standard 885-98 has generated the transfer functions in Table 11.

Sound power data was collected in accordance with ARI Standard 880. Applying the transfer function for sound reduction due to office furnishings, materials, etc. generated the NC data which follows. This is a reference document only provided to address general acoustical issues. What you will find is that the sound in the occupied spaces generated by the VariTrac dampers is minimal when compared to the main HVAC unit sound generation.

Table 11. Acoustical transfer functions

ARI 885-98 Discharge Transfer Function Assumptions

Octave Band

Small Box -24 -28 -39 -53 -59 -40 (<300 cfm) Medium Box -27 -29 240 -51 -53 -39 (<300–700 cfm) Large Box -29 -30 -41 -51 -52 -39 (>700 cfm)

Note: Add to terminal unit sound power to determine discharge sound pressure in the space.

234567

ARI 885-98 Radiated Transfer Function Assumptions

Octave Band

Type 2 Mineral -18 -19 -20 -26 -31 -36 Fiber Insulation

234567

Some general ideas to minimize acoustical issues:

• pay close attention to location of the HVAC unit. This will typically set the overall acoustical quality of your job.

• locate VariTrac dampers outside the occupied space.

• internally lined ductwork can be used to reduce the discharge sound generated by the HVAC unit.

• install flex duct with minimal sagging, and turns.

• locate balancing dampers as far from the diffuser as possible to limit airborne noise.

Note: VariTrac dampers do not carry the ARI seal.

Table 12. Radiated sound data

NC Based on 885-98 Mineral Tile

Size Radiated NC Size

6 in. 3 3 470

8 in. 2 6 840 10 in. 2 5 1310 12 in. 26 1885 14 in. 29 2140 16 in. 21 2515

NC based on maximum rated airflow conditions.

VAV-PRC003-EN 39

Table 13. Discharge sound data

Acoustics

Size CFM ISP NC

Discharge

6 in. 375 0.25 — 6 in. 375 0.5 — 6 in. 375 1 1 8 6 in. 375 2 2 2

6 in. 300 0.25 6 in. 300 0.5 — 6 in. 300 1 — 6 in. 300 2 19

6 in. 225 0.25 — 6 in. 225 0.5 — 6 in. 225 1 — 6 in. 225 2 1 6

6 in. 150 0.25 — 6 in. 150 0.5 — 6 in. 150 1 — 6 in. 150 2 1 6

6 in. 75 0.25 — 6 in. 75 0.5 — 6 in. 75 1 — 6 in. 75 2 16

6 in. 38 0.25 — 6 in. 38 0.5 — 6 in. 38 1 — 6 in. 38 2 15

8 in. 656 0.25 — 8 in. 656 0.5 1 6 8 in. 656 1 2 4 8 in. 656 2 3 0

8 in. 525 0.25 — 8 in. 525 0.5 — 8 in. 525 1 2 0 8 in. 525 2 2 5

8 in. 394 0.25 — 8 in. 394 0.5 — 8 in. 394 1 1 6 8 in. 394 2 2 2

8 in. 263 0.25 — 8 in. 263 0.5 — 8 in. 263 1 — 8 in. 263 2 2 3

8 in. 131 0.25 — 8 in. 131 0.5 — 8 in. 131 1 1 5 8 in. 131 2 2 4

8 in. 66 0.25 — 8 in. 66 0.5 — 8 in. 66 1 — 8 in. 66 2 20

Size CFM ISP NC

Discharge

10 in. 1031 0.25 —

10 in. 1031 0. 5 15 10 in. 1031 1 2 1 10 in. 1031 2 2 7

10 in. 825 0.25 — 10 in. 8 25 0.5 — 10 in. 8 25 1 1 7 10 in. 8 25 2 2 2

10 in. 619 0.25 — 10 in. 619 0.5 — 10 in. 619 1 — 10 in. 619 2 2 0

10 in. 413 0.25 — 10 in. 4 13 0.5 — 10 in. 4 13 1 — 10 in. 4 13 2 19

10 in. 206 0.25 — 10 in. 2 06 0.5 — 10 in. 2 06 1 — 10 in. 2 06 2 19

10 in. 103 0.25 — 10 in. 103 0.5 — 10 in. 103 1 — 10 in. 103 2 1 8

12 in. 1500 0.25 — 12 in. 1500 0.5 15 12 in. 1500 1 21 12 in. 1500 2 29

12 in. 1200 0.25 — 12 in. 1200 0.5 — 12 in. 1200 1 17 12 in. 1200 2 25

12 in. 900 0.25 — 12 in. 9 00 0.5 — 12 in. 9 00 1 — 12 in. 9 00 2 2 2

12 in. 600 0.25 — 12 in. 6 00 0.5 — 12 in. 6 00 1 — 12 in. 6 00 2 2 1

12 in. 300 0.25 — 12 in. 3 00 0.5 — 12 in. 3 00 1 — 12 in. 3 00 2 2 0

12 in. 150 0.25 — 12 in. 1 50 0.5 — 12 in. 1 50 1 — 12 in. 1 50 2 19

Size CFM ISP NC

Discharge

14 in. 2000 0.25 —

14 in. 2000 0.5 17 14 in. 2000 1 24 14 in. 2000 2 30

14 in. 1600 0.25 — 14 in. 1600 0.5 — 14 in. 1600 1 19 14 in. 1600 2 26

14 in. 1200 0.25 — 14 in. 1200 0.5 — 14 in. 1200 1 15 14 in. 1200 2 23

14 in. 800 0.25 — 14 in. 8 00 0.5 — 14 in. 8 00 1 — 14 in. 8 00 2 2 3

14 in. 400 0.25 — 14 in. 4 00 0.5 — 14 in. 4 00 1 — 14 in. 4 00 2 2 3

14 in. 200 0.25 — 14 in. 2 00 0.5 — 14 in. 2 00 1 — 14 in. 2 00 2 2 0

16 in. 2625 0.25 — 16 in. 2625 0.5 17 16 in. 2625 1 25 16 in. 2625 2 32

16 in. 2100 0.25 — 16 in. 2100 0.5 — 16 in. 2100 1 2 3 16 in. 2100 2 2 9

16 in. 1575 0.25 — 16 in. 1575 0.5 — 16 in. 1575 1 22 16 in. 1575 2 27

16 in. 1050 0.25 — 16 in. 1050 0.5 — 16 in. 1050 1 — 16 in. 1050 2 2 2

16 in. 525 0.25 — 16 in. 5 25 0.5 — 16 in. 5 25 1 — 16 in. 5 25 2 2 3

16 in. 263 0.25 — 16 in. 2 63 0.5 — 16 in. 2 63 1 — 16 in. 2 63 2 2 3

Note: NC data based on ARI 885-98 Acoustical transfer functions in Table 11.

40 VAV-PRC003-EN

Dimensions and Weights

Figure 48. Central control panel dimensions

Top view

8.75 in. (22.38 cm)

10.25 in. (26.04 cm)

Front view

2.75 in. (6.99 cm)

Side view

Bottom view

Note:

1. Central control panel weight is 2.5 lbs.

VAV-PRC003-EN 41

Dimensions and Weights

Figure 49. Communicating bypass control dimensions

Mounting holes See back view for dimensions

4 5/16"

6 3/4"

3 3/8"

3 7/8"

0.300"

1.00"

Back View

1.00"

7/8" knockout 1/2" conduit Customer entry

Notes:

Weight 3 1/4 lbs Operating Temp 32˚ to 140˚ Humidity 5 to 95% (non-condensing) Mounting Method Metal screws

4 1/4"

Duct Static Pressure Sensor

Duct Temp Sensor

1 15/16"

3 5/16"

Side View

42 VAV-PRC003-EN

Dimensions and Weights

Figure 50. Round zone and bypass damper dimensions

Airflow

3.625"

8.875"

Damper

Size

10"

12"

14"

16"

Center of Bead

6.375"

8.375"

10.375"

12.375"

14.375"

16.375"

Controls Area

2.00"

12.00"

16.00"

20.00"

4.375"

0.50"

Duct Temp Sensor (Optional)

N/A on Bypass Control

11.125"

13.125"

15.125"

17.125"

19.125"

21.125"

Nominal

CFM

300

500

800

1100

1600

2000

Weight

6 lbs

7 lbs

8 lbs

9 lbs

11 lbs

12 lbs

6.625"

DIA

2.125"

VAV-PRC003-EN 43

Dimensions and Weights

Figure 51. Rectangular zone damper dimensions

16.00" Ref.

Seam

Slip & Drive Connection

Dimensions

8.00"

10.00"

14.00"

12.00"

14.00"

16.00"

20.00"

18.00"

6.00" Ref.

Frame

Blades

Gear Blade Pin

Damper Frame Data

16-gage galvanized steel 16-gage galvanized steel

All blades are 3.19" nominal width and 8" maximum

ABS plastic

3/8" rolled steel, zinc plated

44 VAV-PRC003-EN

Dimensions and Weights

Figure 52 Rectangular bypass damper dimensions

Hub

1.20"

1.10"

.70"

Actuator Dimensions

Dimensions

14" 12"

16"

20"

30"

16"

20"

16" Ref

Seam

Air Flo

Actuator

Wiring Red

CCW

White

COM

Black

Damper Frame Data

Fram e

Blades

Linkage Blade Pin Blade Pin Extension

Bearings

Blade Seals

Side Seals Cable Weight

13 gage galvanized steel

16 gage galvanized steel; blades are 6" nominal width and 8" maximum

1/8" rolled steel, zinc plated

3/8" square steel, zinc plated

7/16" diameter, 7" long Included with all dampers

Self-lubricating acetol

None

10"

CCP Close

Com

Open

Seam

Factory Installed Cable Provided

Actuator

VAV-PRC003-EN 45

Dimensions and Weights

Figure 53. Occupancy Sensor

3.60"

Front View

Figure 54. CO2 Sensor dimensions

3.125"

4.25"

Figure 55. Digital Zone Sensor

2.8

1.44"

1.1

1.0

˚F

˚C

MAX

UNOCC SETPOINT OVERRIDE

2.50"

4.5

Side View

1.90"

CANCEL

46 VAV-PRC003-EN

Glossary

ABS gears – Gears formed of a

lightweight plastic known for its toughness, impact strength, and dimensional stability.

Back draft damper – A one-way airflow damper in a parallel fan powered unit prevents primary flow from exiting the plenem inlet.

Binary input – A two-position signal indicating on/off status.

Binary output – A control output that is either on or off.

Built-in time clock – The occupancy timer included in the CCP operator display.

Bypass damper – The motorized damper ducted between the system supply and return ducts used to control static pressure in changeover bypass VAV systems.

Central control panel (CCP) – The system level control device in a Trane changeover bypass or delivered VAV system that gathers data from zone controllers and operates the HVAC unit to maintain the correct air flow and temperature.

Changeover-bypass VAV – A control that provides variable air volume functionality to a constant volume air handling system.

sensor – An analog sensor that

detects and measures carbon dioxide sensor to determine occupancy level.

Commissioning – The process of starting up and verifying correct operation of a building system.

Conditioned air – Air that is heated, cooled, humidified, or dehumidified to maintain comfort in an interior space.

Constant volume – An air distribution system that varies the temperature of a fixed volume of air to maintain space comfort.

Delivered VAV – A self configuring system providing true pressure independent VAV control to smaller building applications. Delivered VAV requires a CCP with operator display, a

Commercial Voyager VAV rooftop unit and VariTrane VAV boxes.

Demand control ventilation – A method of maintaining indoor air quality through intelligent ventilation based on occupancy. The quantity of ventilation is controlled based on indoor CO2 levels, which correlate to occupancy levels. Demand controlled ventilation saves money by reducing ventilation during periods of low occupancy.

Direct-expansion (DX) – When the refrigerant in the system is either condensed or evaporated directly by the medium being heated or cooled.

Discharge air (DA) – Air discharged from the air handler into the ducts.

Discharge air control – An air handling system that provides fixed temperature air (either fixed or variable volume). Other control devices vary the actual volume of air delivered to the space to maintain occupant comfort.

Economizer – A damper arrangement and automatic control system that allows a heating, ventilation and air conditioning (HVAC) system to supply up to 100 percent outside air to satisfy cooling demands, even if additional mechanical cooling is required

Exception schedule – A one time only time of day schedule in a system that is removed automatically after use

Free cooling – Outdoor air introduced to a system under correct conditions to provided cooling to a space. Also see also “Economizer”

HVAC Unit – An air moving device that conditions air. An HVAC unit may provide cooling, or heating and cooling. Typical HVAC units include packaged rooftop units, split systems, and water source heat pumps.

LCD – Liquid crystal display

NDIR – Non-dispersive infrared

technology

Negative pressure – The condition that exists when more air is exhausted from a space than is supplied.

Non-volatile memory – System memory that retains programming with no battery or capacitor back up required

Normally closed (NC) – Electrical contacts that are closed (current flows) in the de-energized condition

Normally open (NO) – Electrical contacts that are open (no current flows) in the de-energized condition

Occupancy sensor – A binary sensor that transmits a signal upon detection of movement in the coverage area

Outdoor air (OA) – This is fresh air drawn in to provide space ventilation. Also see ‘Ventilation air”

Outdoor air damper – The damper that draws fresh air into the air handling system for ventilation. Also referred to as the ventilation or fresh air damper

Override – A manual or automatic action taken to bypass normal operation

Packaged unitary system – An air handling system with all the major components contained in a single cabinet or installed in a single location

PIR – Passive infrared sensing technology (used in occupancy and motion detection sensors)

Polling – The method a VariTrac CCP uses to determine the need for heating or cooling from the air handling system by examining the zone requirements

Positive pressure – The condition that exists when more air is supplied to a space than is exhausted.

Pressure-dependent VAV control – A VAV unit with airflow quantity dependent upon static pressure. There is no zone flow sensor in pressure dependent VAV boxes.

Pressure-independent VAV control – A VAV unit with airflow

quantity independent of duct static pressure. Actual airflow to the space is measured and controlled by an airflow sensor in the pressure independent VAV box.

VAV-PRC003-EN 47

Glossary

Priority shutdown – An immediate

shutdown of the fan and heating or cooling stages in a VariTrac changeover bypass or Delivered VAV system caused by either the loss of critical system information or an external priority shutdown input

Pulse-width modulating reheat – Reheat that operates duct mounted electric coils on a 0-100% duty cycle in response to increased space heating demand.

Reheat device – A source of heat located downstream from a control device such as a VAV box to add heat to air entering a space to provide occupant comfort

ReliaTel (RTRM) – The latest generation Trane factory mounted unitary controller.

Return air (RA) – Air returned to the air handler from the conditioned space, to be reconditioned.

Setpoint – The desired room temperature to be achieved and maintained by an HVAC system.

Setpoint limit – An electronic or manual constraint imposed on a setpoint to prevent misadjustment

SPDT – A relay with of one set of normally-open, normally-closed contacts

Staged electric reheat – Reheat that operates one or more duct mounted electric coils in a series in response to increased space heating demand.

Staged (or perimeter) hot water reheat – Reheat that operates duct-

mounted hot water or space-mounted electric or hot water reheat coils in response to increased space heating demand

Static pressure – The difference between the air pressure on the inside of the duct and outside of the duct. Static pressure is an indicator of how much pressure the fans are creating and how effective they will be at distributing the supply air through the ducts.

Supply air (SA) – air which blows out of the air handler into the ducts. See also “Discharge air (DA)”

Terminal unit – HVAC equipment that provides comfort directly to a space.

Thermal requirements – The heating or cooling load requirements for a specific area or space in a building. Care must be taken to not control areas with different thermal requirements from one air handling system

Touch-screen operator display – The LCD panel mounted onto a VariTrac CCP to allow direct user interface and time of day programming for the system

Unit control module UCM – A Trane microelectronic circuit board that controls individual HVAC equipment. May link to an Integrated Comfort System

Unitary – one or more factory-made assemblies which normally include an evaporator or cooling coil, an air moving device, and a compressor and condenser combination

Variable air volume (VAV) – an air handling system that varies the volume (amount) of constant temperature air to a space to control comfort

VariTrac – The Trane changeover bypass VAV system

VariTrane – The Trane pressure independent VAV box

VAV box – The damper or air valve (plus associated controller) that controls the zone air volume in a VAV system. Also see “Variable air volume”

Ventilation air – The outdoor air drawn into the HVAC unit to provide fresh air to the space. Also see “Outdoor air (OA)”

Voting – See “Polling”

Zone sensor – The device that

measures a variable (usually temperature) in a space and sends it to a controller. Commonly referred to as a thermostat.

48 VAV-PRC003-EN

VAV-PRC003-EN 49

50 VAV-PRC003-EN

VAV-PRC003-EN 51

Trane A business of American Standard Companies www.trane.com

Literature Order Number VAV-PRC003-EN

File Number PL-TD-VAV-000-PRC003-EN-0604

Supersedes VAV-DS-12

Stocking Location La Crosse

For more information contact your local district office or email 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.

Trane 3VAV-PRC003 User Manual [EN]

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Introduction

Features and Benefits

Application Considerations

Selection Procedures

Electrical Data and Connections

Specifications

Acoustics

Dimensions and Weights

Glossary