Comfort Stat CDT901 - Manual (Page 92)

CDT900 Series Touchscreen Programmable Thermostata
Fig. 32. L terminal switch to R (power)
side of system transformer.
1.Choose correct heat pump application in
Installer Setup Number 0170.
2.Choose Fossil Fuel Option as the
backup heat source in Installer Setup
Number 0200.
3.Choose No External Fossil Fuel Kit
Option is control- ling back up heat in
Installer Setup Number 0210.
4.Choose Outdoor Temperature Sensor
for Heat PumpTemperature Lockouts
Option in Installer Setup Num- ber 0340.
5.Choose appropriate Balance Point
Temperature in Installer Setup Number
0350.
OPERATION IN HEAT MODE ABOVE BALANCE
POINT (OUTDOOR TEMPERATURE)
When the outdoor temperature is above
the selected Balance Point Temperature
(ISU 0350), only the compressor operates
and the fan (G terminal) energizes when
the thermostat calls for heat. See Fig. 33.
BALANCE
POINT
OUT
D
OO
R
TEMP
ERA
T
U
R
E
COMPRESSOR ONLY
FOSSIL FUEL ONLY
Fig. 33. Dual Fuel Heat Pump Operation in
Heat mode with
OPERATION IN HEAT MODE BELOW BALANCE
POINT (OUTDOOR TEMPERATURE)
When the outdoor temperature is below the
selected Balance Point Temperature (ISU
0350), only the Fossil Fuel (auxiliary heat)
operates and the fan (G terminal) does not
energize when the thermostat calls for heat
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