Honeywell T8501 Installation Instructions Manual page 11

Symptom Possible Cause
Cooling will not No power to the thermostat.
come on.
Thermostat minimum off time is
activated.
System selection is not set to
Cool.
System on indicator Fan operation set for 00
is displayed, but no (conventional heat) when it
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
setpoint.
Heating equipment is not
operating.
Outdoor tempera- Option not activated.
a
ture not displayed
Outdoor Outdoor sensor is connected
temperature incorrectly.
a
display is incorrect
Wrong sensor.
a
Select Models
Table 5. Troubleshooting Guide. (Continued)
• 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 power switch on the HVAC 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 number 33. Reconfigure minimum off
time (if required).
Set system selection to Cool.
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 self-test.
Enter Installer Setup 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.
11
T8501 MICROELECTRONIC THERMOSTATS
Action
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