69-0927—4
9
T8511G,R MICROELECTRONIC HEAT PUMP THERMOSTATS
M4867

5. Press the increase ▲ key again to display the

EEPROM identification code.

(Example: 222 = EEPROM ID 222)

6. Press and hold the increase ▲ and decrease ▼

keys together, until the room temperature is

displayed, to exit the system-test. The system-test

times out after five minutes without any key presses.

CHECKOUT

Outdoor Temperature Sensor

(Where Applicable)

Allow the outdoor temperature sensor to soak in the

outdoor air for a minimum of five minutes before taking a

reading. With an accurate thermometer (±1°F [±0.5°C]),

measure the temperature at the sensor location, allowing

time for the thermometer to stabilize before reading. Match

the thermometer reading to the outdoor temperature

display at the thermostat.

Symptom Possible Cause Action
Display will not
come on. Thermostat is not being
powered. • 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 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.
Thermostat microprocessor is
locked up. Remove the thermostat from the wallplate for 2 minutes. After
2 minutes, replace the thermostat on the wallplate.
Temperature
display is incorrect. Room temperature display has
been reconfigured. Enter Installer Setup mode number 37 and reconfigure the
display.
Thermostat is configured for °F
or °C display
a
.Enter Installer Setup mode number 14 and reconfigure the
display.
Bad thermostat location. Relocate the thermostat.
Temperature
settings will not
change. (Example:
Cannot set the
The upper or lower temperature
limits were reached.
Check the temperature setpoints:
• Heating limits are 40 to 90°F (4.5 to 32°C)
• T8511R cooling limits are 45 to 99°F (7 to 35°C) and
T8511G cooling limits are 48 to 99°F
heating higher or
the cooling lower.) The setpoint temperature range
stops were configured. Check Installer Setup mode numbers 34 and 35 and
reconfigure the setpoint stops.
Heating 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 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.
TROUBLESHOOTING GUIDE
aAvailable on select models.
(Continued)