Honeywell DMULTISTAGE T8524C Installation Instructions Manual page 9

TROUBLESHOOTING GUIDE (Continued)
Symptom
Heating will not No power to the thermostat.
come on.
Heating will not Thermostat minimum off time is
come on. activated.
System selection is not set to
Heat.
Heating setpoint is below room
temperature.
Cooling will not No power to the thermostat.
come on.
Thermostat minimum off time is
activated.
System selection is not set to
Cool.
Cooling setpoint is above room
temperature.
Heating or cooling Heat or cool circuit is opening
comes on up or becoming high
momentarily and impedance.
shuts off
System On Fan operation set for 00
indicator is lit, but (conventional heat) when it
no heat is being should be set for 01 (electric
delivered. heat).
Conventional heating
equipment turns on the fan
when the furnace has
warmed up to a setpoint.
Heating equipment is not
operating.
Outdoor Option not activated.
temperature
a
not displayed
Outdoor sensor is connected
Outdoor
incorrectly.
temperature
a
display is incorrect
Wrong sensor.
a
Available on select models.
T8524C,D MULTISTAGE MICROELECTRONIC THERMOSTATS
Possible Cause
• Check that C terminal is connected to the system
transformer.
• Check for 24 Vac between C and R or RH terminals.
— If missing 24 Vac:
— check if the circuit breaker is tripped—reset the
circuit breaker.
— check if the system fuse is blown—replace the fuse.
— check if the system switch at the equipment is in the
Off position—set to On position.
— check wiring between thermostat and HVAC
equipment—replace any broken wires and tighten
any loose connections.
— If 24 Vac is present, proceed with troubleshooting.
Wait up to five minutes for the system to respond.
Set system selection to Heat.
Check heating setpoint. Set heating setpoint to desired
temperature.
• Check that C terminal is connected to the system
transformer.
• Check for 24 Vac between C and R or RC and Y terminals.
— If missing 24 Vac:
— check if the circuit breaker is tripped—reset the
circuit breaker.
— check if the system fuse is blown—replace the fuse.
— check if the system switch at the equipment is in the
Off position—set to the On position.
— check wiring between thermostat and HVAC
equipment—replace any broken wires and tighten
any loose connections.
— If 24 Vac is present, proceed with troubleshooting.
• Wait up to five minutes for the system to respond.
• Enter Installer Setup mode number 33. Reconfigure
minimum off time (if required).
Set system selection to Cool.
Check cooling setpoint. Set cooling setpoint to desired
temperature.
Add resistor in parallel with load or install interface relay.
Enter Installer Setup mode number 02 and reconfigure the fan
operation.
Wait a minute after seeing the On indicator and then check the
registers.
Verify operation of heating equipment in system test.
Enter Installer Setup mode number 24 and set to 01.
Thermostat must have OT terminals and a C7089B1000
installed.
Refer to C7089B1000 installation instructions and check wiring
between the thermostat and sensor.
Replace sensor with C7089B1000 sensor.
9
Action
69-1055-1