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4 VAV-PRC003-EN
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
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
2
and occupancy
sensor inputs
• A digital display zone sensor for
simplified occupant control
VariTrac Product
Enhancements
Advanced Control Options
Some of the VariTrac intelligent system
control features are listed below.
•CO
2
-based demand control ventilation
resets the position of the HVAC unit
ventilation air damper when zone CO
2
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
Figure 2. The VariTrac CCP with
optional touch-screen interface
simplifies system operation with
intuitive icon-driven design
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 multiple-
space 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.
Introduction