VISIONPRO® IAQ TOTAL HOME COMFORT SYSTEM
68-0287—1 22
Heat Pump Emergency Heat LED Indication
The thermostat uses a red LED indicator that lights when the
thermostat is in the Emergency Heat mode. The LED is located
in the upper right corner of the thermostat. It is visible only
when on.
Heat Pump Temperature Lockouts

Dual Fuel Heat Pump and Outdoor Temperature

Sensor

In this operation, there is no external fossil fuel kit (dual fuel kit)
installed; the thermostat controls this function.
1. Choose correct heat pump application in Installer Setup
Number 0172.
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 Pump
Temperature Lockouts in Installer Setup Number 0342.
5. Choose appropriate Balance Point Temperature in
Installer Setup Number 0350.
Dual Fuel Heat Pump Control

Balance Point Only (ISU345 = 0)

NOTE: System must have an outdoor temperature sensor.
When the outdoor temperature is above the selected balance
point temperature, only the compressor operates and the fan
(G terminal) energizes when the thermostat calls for heat. See
Fig. 30. When the outdoor temperature is below the selected
balance point temperature, only the fossil fuel (auxiliary heat)
operates and the fan (G terminal) does not energize when the
thermostat calls for heat.
Fig. 30. Dual Fuel Heat Pump Operation in Heat mode with
Balance Point Set.

Balance Point Plus 2° Droop (ISU345 = 1)

The fossil fuel will turn on when the outdoor temperature is
above the balance point if the room temperature droops
approximately 2 degrees below the temperature setting, and
the compressor will be disabled.

Balance Point/Auxiliary Heat Lockout Plus 2° Droop

(ISU 345 = 2)

When the outdoor temperature is above the Auxiliary Heat
Lockout Temperature only the compressor operates; below the
balance point temperature (setup function 0360) only the fossil
fuel operates. Between the balance point temperature and
auxiliary heat lockout temperature the compressor will operate.
However, the fossil fuel will turn on if the room temperature
droops approximately 2°F below the temperature setting,
compressor will be disabled.
Fig. 31. Balance Point with Auxiliary Lockout Temperature.
AUXILIARY LOCKOUT FOR ELECTRIC HEAT BACKUP
Heat Pump systems with electric heat backup can select a
compressor lockout temperature (function 0350) and/or
auxiliary heat lockout temperature (function 0360). When the
outdoor temperature is below the compressor lockout
temperature, only the auxiliary heat operates. When the
outdoor temperature is between the compressor and auxiliary
lockout temperatures, both the compressor and auxiliary heat
can operate.
NOTE: System must have an outdoor temperature sensor.

Heat Pump with Electric Auxiliary (Backup) Heat and

Outdoor Temperature Sensor

1. Choose correct heat pump application in Installer Setup
Number 0172.
2. Choose Electric as Auxiliary (Backup) Heat Source in
Installer Setup Number 0200.
3. Choose Outdoor Temperature Sensor in Installer
Setup Number 0342.
4. Choose Compressor Lockout Temperature in Installer
Setup Number 0350.
5. Choose Auxiliary Lockout Temperature in Installer
Setup Number 0360.
NOTE: There is a 5°F deadband between the Compressor
and Auxiliary Heat Lockout Temperatures.

Operation in Heat Mode

When the outdoor temperature is below the Compressor
Lockout Temperature, only the Auxiliary Heat operates.
When the outdoor temperature is above the Auxiliary Lockout
Temperature, only the Compressor operates. See Fig. 32.
30
M22441
BALANCE
POINT
COMPRESSOR ONLY
FOSSIL FUEL ONLY
OUTDOOR TEMPERATURE
50
35
OUTDOOR TEMPERATURE
BALANCE
POINT
AUX.
LOCKOUT
COMPRESSOR ONLY
COMPRESSOR+2 °F
DROOP UPSTAGE TO
FURNACE
FURNACE ONLY
M23497