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Symptom Cause
Thermostat does not call for heat
Minimum-off times. Change the mode to OFF first, then change the mode to
HEAT and make a call for heat.
Heating does not come on at all
RH terminal not connected – see wiring diagrams.
Heating equipment power not on.
Auxiliary Heat does not come on
High Balance point limit – set balance point higher than outdoor temperature
or disconnect outdoor temperature sensor during system checkout.
Furnace plenum sensor keeps fan on – normal.
Fan stays on after heat call
Blower Extension for humidifier operation. Verify that the message
"HUMIDIFYING" appears at the message center, alternating with the time
and date and any other currently active messages.
Fan comes on before heat starts, or
Change position of ELEC/GAS dip switch – ELEC for electric heat systems
Fan does not come on with heat
(fan on with heat call) or to GAS for fossil fuel systems where the fan is
controlled internally by the heating equipment.
Cooling comes on instead of heat
Reversing valve wiring.
Miswiring – check wire colors at thermostat and HVAC equipment.
Takes longer than 4 minutes for auxiliary SINGLE/MULTI dip switch set incorrectly – set to SINGLE for single-stage
heat to come on after compressor heat. compressor systems.
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TROUBLESHOOTING – HEATING OPERATION