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TB7220 COMMERCIALPRO™ PROGRAMMABLE THERMOSTAT
63-2635—03 22
TROUBLESHOOTING (TABLE 11)
Table 11. Troubleshooting.
Symptom Possible Cause Action
Display does not come on. Thermostat is not being powered. Check for 24 Vac between C and Rc.
Check that AAA batteries are installed correctly
and are good.
Temperature settings do not
change.
The upper or lower temperature limits were
reached.
Check temperature setpoints.
Check ISU 0600 and 0610; modify as needed.
The keypad is fully locked. Check ISU 0670 to change keypad locked
options.
Heating or cooling does not come
on.
Thermostat minimum off-time is activated. Wait up to five minutes for the system to respond.
System selection is not set to Heat or Cool. Set system Selection to correct position.
System type Selection is incorrect. Check ISU 0170 and make sure correct System
type is chosen.
Thermostat is calling for Heat
(Heat on) or Cool (Cool on) but
no heating or cooling is running.
Heating or cooling equipment is not
operating.
Check wiring.
Check ISU 0170 and make sure correct system
type is chosen.
Verify operation of equipment in System Test
mode.
Heat does not turn on (Heat On is
solid in the display).
Heating equipment failure. Check for 24 Vac at the equipment on the
secondary side of the transformer between power
and common. If voltage is not present, check the
heating equipment to find the cause of the
problem.
Check for 24 Vac between the heat terminal (W)
and transformer common. If 24 Vac is present, the
thermostat is functional. Check the heating
equipment to find the cause of the problem.
Loose or broken wire connection between
thermostat and heating equipment.
Check for 24 Vac between the heat terminal (W)
and transformer common. If voltage is not
present, check wire connection (loose or broken)
between the thermostat and the heating
equipment.
Cooling does not turn on (Cool
On is solid in the display).
Cooling equipment failure. Check for 24 Vac at the equipment on the
secondary side of the transformer between power
and common. If voltage is not present, check the
cooling equipment to find the cause of the
problem.
Check for 24 Vac between the cool terminal (Y)
and transformer common. If 24 Vac is present, the
thermostat is functional. Check the cooling
equipment to find the cause of the problem.
Loose or broken wire connection between
thermostat and cooling equipment.
Check for 24 Vac between the cool terminal (Y)
and transformer common. If voltage is not
present, check the wire connection (loose or
broken) between the thermostat and the cooling
equipment.
Fan does not turn on in a call for
heat (electric furnace).
Fan Control in Heating is set to Gas or Oil
Furnace (Setting 0180).
Set Fan Control in Heating to Electric Furnace
(Setting 0180).
Heat pump puts out cool air in the
heat mode and warm air in the
cool mode.
Changeover Valve (ISU 0190) is not
configured to match the changeover
required by the installed heat pump.
Set Changeover Valve (ISU 0190) to match the
changeover required by the installed heat pump.
Both the heating and cooling
equipment are running at the
same time.
The heating equipment is not a heat pump
but the System Type (ISU 0170) is set to
Heat Pump.
Set System Type (ISU 0170) to match the
installed heating and/or cooling equipment.
Heating and cooling wires are shorted
together.
Separate the shorted heating and cooling wires.