1
System Controller
Leaving Air Sensor
Zone Damper
Zone Thermostat
Bypass Damper
Damper
Transformer
1
2
3
4
5
6
*The DigiTract 4 was designed for both residential and
commercial applications of 4 or less zones. The full
spectrum of supply dampers can be applied, from low
pressure; medium pressure; and heavy duty; round and
rectangular.
Fused 24V Transformer
D
IGITRACT 4
System Controller
73
73
73
73
5
2
3
1
4
6
ZONE 4
ZONE 3
ZONE 2
ZONE 1
LAT
INTRODUCTION
The Digitract 4 zoning system enables up to four room thermostats to control a single HVAC system. This permits superior
building temperature control over a standard single thermostat. Any generic thermostat may be used on this control
system. When using digital thermostats, they must have “C” terminal for common or be battery powered. Both Programma-
ble and Non-Programmable thermostats can be used. This system is designed to be installed and serviced by qualified
licensed professionals.
SYSTEM DESCRIPTION
The Digitract 4 zoning system consists of 2-stage system controller
with built-in capacity control (leaving air sensor), zone dampers,
field suppled zone thermostats, bypass damper and damper trans
-
former.
The
System Controller
is the heart of the Digitract 4 zoning system.
It monitors the leaving air temperature, zone thermostats and
controls the HVAC system and zone dampers. See page 6-10 for
further information.
The
Leaving Air Sensor (LAT)
is part of the staging and capacity
control feature of the system controller. It is a sensor placed in the
supply air of the HVAC system. The sensor monitors the supply air
temperature of the HVAC system and sends this information to the
system controller. The system controller uses this information to
stage and temporarily cycle the HVAC system off if the leaving air
gets too hot in heat mode or too cold in cool mode. For heat
pumps, this input is also used to control the auxiliary heat. See
Capacity Controller section on page 11, for further information.
Balance Point
is used for fossil fuel applications when an FOAS is
applied. The balance point feature will lock out compressor and
enable gas furnace when outside air temperature drops below BP
(balance point) setting.
The
Zone Dampers
are air valves placed in the forced air duct work
for each zone. They are controlled by the system controller. While
ostats not calling will close and zone dampers for the zones
calling will remain open. Conditioned air is only directed to the
zones needing it. See pages 13-17 for further information.
The
Zone Thermostats
monitor the room temperature of each
zone and compare it to the heat and cool setpoints stored in
them. If the room temperature drops below the heat setpoint, the
zone thermostat makes a heat call telling the system controller
that zone needs heating. If the room temperature rises above the
cool setpoint, that thermostat makes a cool call telling the system
controller that zone needs cooling. Two-stage thermostats are not
required with the Digitract 4 system. The system controller will
cycle staging and auxiliary strip heat base on leaving air tempera-
ture and time.
The
Bypass Damper
is a pressure relief valve placed between the
supply and return ducts of the forced air duct work. As zone
dampers start closing, the bypass damper will open and divert
some of the supply air to the return. This prvents a pressure build-
up in the supply duct which can cause fan cavitation, excessive air
velocities, and excessive zone damper blow-by. See pages 17-22
for further information.
Damper Transformer
is wired to TR1 and TR2 on the system
controller and powers the zone dampers only. Requires an in-line
fuse. See Damper Transformer section, page 23.
