T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS
TROUBLESHOOTING GUIDE
Table 6. Troubleshooting Guide.
Possible Cause
Symptom
Action
Display will not
come on.
Thermostat is not being
powered.
• Check for 24 Vac between R and C 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
Temperature
Room temperature display has Enter Installer Setup number 37 and reconfigure the display.
display is incorrect. been reconfigured.
Thermostat is configured for °F Enter Installer Setup number 14 and reconfigure the display.
or °C display.
Bad thermostat location.
Relocate the thermostat.
Temperature
The upper or lower temperature Check the temperature setpoints:
limits were reached. • Heating limits are 40 to 90°F (7 to 31°C).
• Cooling limits are 48 to 99°F (9 to 37°C).
settings will not
change. (Example:
Cannot set the
heating higher or
the cooling lower.)
The setpoint temperature range Check Installer Setup numbers 34 and 35 and reconfigure the
stops were configured.
setpoint stops.
Heating will not
come on.
No power to the thermostat.
• Check for 24 Vac between R and W 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 minimum off time is Wait up to five minutes for the system to respond.
activated.
System selection is not set to
Heat.
Set system selection to Heat.
Heating setpoint is below room Check heating setpoint. Set heating setpoint to desired
temperature.
temperature.
Cooling will not
come on.
No power to the thermostat.
• Check for 24 Vac between R or RC.
— 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 minimum off time is • Wait up to five minutes for the system to respond.
activated.
• Enter Installer Setup number 33. Reconfigure minimum off
time (if required).
System selection is not set to
Cool.
Set system selection to Cool.
Cool setpoint is above room
temperature.
Check cooling setpoint. Set cooling setpoint to desired
temperature.
11
69-1412—1