TB8220U COMMERCIAL VISIONPRO™ PROGRAMMABLE THERMOSTAT
62-3070—07
14
Table 7. 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 Installer Setup Numbers 0600 and
0610; modify as needed.
The keypad is fully locked.
Check Installer Setup Number 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 not set to Heat or
Cool.
Set system Selection to correct position.
System type Selection is incorrect.
Check Installer Setup Number 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 Installer Setup Number 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.
Heat pump puts out cool air in
the heat mode and warm air in
the cool mode.
Changeover Valve (Installer Setup
Number 0190) is not configured to
match the changeover required by the
installed heat pump.
Set Changeover Valve (Installer Setup
Number 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 (Installer
Setup Number 0170) is set to Heat
Pump.
Set System Type (Installer Setup Number
0170) to match the installed heating and/or
cooling equipment.
Heating and cooling wires are shorted
together.
Separate the shorted heating and cooling
wires.
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.
