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TROUBLESHOOTING
Table 8 provides troubleshooting information.
Symptom
Display does not
come on.
Temperature settings
do not change.
Heating or cooling
does not come on.
Thermostat is calling
for Heat (Heat on) or
Cool (Cool on) but no
heating or cooling is
running.
Heat does not turn on
(Heat On is solid in
the display).
Both the heating and
cooling equipment are
running at the same
time.
Table 8. Troubleshooting.
Possible Cause
Thermostat is not being
powered.
The upper or lower
temperature limits were
reached.
The keypad is fully locked. Change keypad locked options (Installer Setup code #18).
System Type selection not
set to Heat or Cool or the
selection is incorrect.
Heating or cooling
equipment is not
operating.
Heating equipment failure. For TB6575A/B:
Loose connection or
broken wire between
thermostat and heating
equipment.
Incorrect System Type
selected.
Heating and cooling wires
are shorted together.
TB6575/TB8575 DIGITAL FAN COIL THERMOSTATS
For TB6575A/B, check for 120/240 Vac between L and N.
For TB8575A, check for 24 Vac between R and C.
Check the temperature setpoints for heating and cooling (Installer
Setup codes 16 and 17 respectively). Modify as needed.
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.
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.
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.
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.
Check that the Installer Setup code #2 (System Type) value
matches the installed heating and/or cooling equipment.
Separate the shorted heating and cooling wires.
17
Action
62-0311—05
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