TB6575/TB8575 DIGITAL FAN COIL THERMOSTATS
17
62-0311—05
TROUBLESHOOTING
Table 8 provides troubleshooting information.
Table 8. Troubleshooting.
Symptom Possible
Cause
Action
Display does not
come on.
Thermostat is not being
powered.
For TB6575A/B, check for 120/240 Vac between L and N.
For TB8575A, check for 24 Vac between R and C.
Temperature settings
do not change.
The upper or lower
temperature limits were
reached.
Check the temperature setpoints for heating and cooling (Installer
Setup codes 16 and 17 respectively). Modify as needed.
The keypad is fully locked. Change keypad locked options (Installer Setup code #18).
Heating or cooling
does not come on.
System Type selection not
set to Heat or Cool or the
selection is incorrect.
Set the Installer Setup code #2 (System Type) to the correct value
to match the installed heating and/or cooling equipment. Verify
operation of wiring and equipment in Installer Test mode.
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 that the Installer Setup code #2 (System
Type) value matches the installed heating and/or cooling
equipment. Verify operation of equipment in Installer Test mode.
Heat does not turn on
(Heat On is solid in
the display).
Heating equipment failure. For TB6575A/B:
1.
Check for 120/240 Vac at the equipment between power and
common, (terminals L and N).
2.
Check for 120/240 Vac between the heat (W) and common
(N) terminals. If 120/240 Vac is present, the thermostat is
functional.
For TB8575A:
1.
Check for 24 Vac at the equipment on the secondary side of
the transformer between power and common (terminals R
and C).
2.
Check for 24 Vac between the heat terminal (W) and trans-
former common. If 24 Vac is present, the thermostat is func-
tional.
If voltage is present, check the heating equipment to find the cause
of the problem.
Loose connection or
broken wire between
thermostat and heating
equipment.
For TB6575A/B:
Check for 120/240 Vac between the heat (W) and common (N)
terminals.
For TB8575A:
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.
Both the heating and
cooling equipment are
running at the same
time.
Incorrect System Type
selected.
Check that the Installer Setup code #2 (System Type) value
matches the installed heating and/or cooling equipment.
Heating and cooling wires
are shorted together.
Separate the shorted heating and cooling wires.