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69-0927—4
10
T8511G,R MICROELECTRONIC HEAT PUMP THERMOSTATS
Symptom Possible Cause Action
Heating will not
come on.
Thermostat minimum off time is
activated.
Wait up to five minutes for the system to respond.
(Continued)
System selection is not set to
Heat.
Set system selection to Heat.
O/B terminal configured
incorrectly
a
.
Check Installer Setup mode number 29 and reconfigure
correctly.
O or B terminal miswired
a
. Check system description to determine whether changeover
should be energized in heat (B) or cool (O). Rewire if
necessary.
Cooling will not
come on.
No power to the thermostat. • 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.
Thermostat minimum off time is
activated.
• Wait up to five minutes for the system to respond.
• Enter Installer Setup mode number 33. Reconfigure
minimum off time (if required).
System selection is not set to
Cool.
Set system selection to Cool.
O/B terminal configured
incorrectly
a
.
Check Installer Setup mode number 29 and reconfigure
correctly.
O or B terminal miswired
a
. Check system description to determine whether changeover
should be energized in heat (B) or cool (O). Rewire if
necessary.
System On
indicator is lit, but
no heat is being
delivered.
Heating equipment is not
operating.
Verify operation of heating equipment in self-test.
TROUBLESHOOTING GUIDE (Continued)
a
Available on select models.