Troubleshooting Guide - Honeywell T8511 Manual

T8501 AND T8511 DELUXE ELECTRONIC THERMOSTATS
TROUBLESHOOTING GUIDE (continued)
Symptom
Heating will not come on.
Cooling will not come on.
System On indicator is lit,
but no heat is being
delivered.
Outdoor temperature
not displayed (select
models)
Outdoor temperature
display is incorrect (select
models)
68-0162—1
Possible Cause
No power to the • Check that C terminal is connected to the system transformer.
thermostat. • Check for 24 Vac between C and R or RH terminals.
— If missing 24 Vac:
— If 24 Vac is present, proceed with troubleshooting.
Thermostat minimum off Wait up to five minutes for the system to respond.
time is activated.
System selection is not Set system selection to Heat.
set to Heat.
O/B terminal configured Check Installer Setup number 29 and reconfigure correctly.
incorrectly (select
models).
O or B terminal Check system description to determine whether changeover should be
miswired (select energized in heat (B) or cool (O). Rewire if necessary.
models).
No power to the • Check that C terminal is connected to the system transformer.
thermostat. • Check for 24 Vac between C and R or RC and Y terminals.
— If missing 24 Vac:
— If 24 Vac is present, proceed with troubleshooting.
Thermostat minimum off • Wait up to five minutes for the system to respond.
time is activated. • Enter Installer Setup mode number 33. Reconfigure minimum off
System selection is not Set system selection to Cool.
set to Cool.
O/B terminal configured Check Installer Setup number 29 and reconfigure correctly.
incorrectly (select
models).
O or B terminal Check system description to determine whether changeover should be
miswired (select energized in heat (B) or cool (O). Rewire if necessary.
models).
Heating equipment is Verify operation of heating equipment in system test.
not operating.
Option not activated. Enter Installer Setup number 24 and set to 01. Thermostat must have
OT terminals and a C7089B1000 installed.
Outdoor sensor is Refer to C7089B1000 installation instructions and check wiring
connected incorrectly. between the thermostat and sensor.
Wrong sensor. Replace sensor with C7089B1000 sensor.
— 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.
— 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.
time (if required).
14
Action