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Troubleshooting
Symptom
Temperature display
seems inaccurate
"Locked" appears on LCD
and heating or cooling will
not operate.
Heating or cooling runs in
dead band.
SMT‐770 has no display
Reversing valve remains
energised after heating or
cooling has stopped.
Spanner Symbol flashes on
LCD
E.Heat or E.Heating is
shown on LCD without
manually selecting it.
44 | P a g e
Suspected Fault
Air from the wall cavity may be leaking into the
rear of the thermostat / sensor enclosure.
The internally fitted temperature sensor is
folded back inside the Chameleon and not being
exposed to the room air temperature.
External heat or cool source such as lamps,
televisions or drafts from open doors affecting
the accuracy of sensor.
Sensor calibration may setting are incorrect
This is not a fault.
Outside air temp to high to require heating
Outside air temp to low to require cooling.
SMT‐770 incorrectly set to HP mode.
(SMT‐770 keeps reversing valve energised after
heating / cooling has stopped to limit
decompression noise from AC system.)
Minimum run period has not yet expired. Words
"Heating" or "Cooling flash in the LCD
Compressor and reversing valve wiring crossed
in HP mode (sw2=on)
Power failure or faulty SMT‐770
This is not a fault
This is not a fault
Commissioning mode enabled.
This is not a fault.
Suggested remedy
Plug holes in wall with tape to prevent leaks
Carefully move the room temperature
sensor bead so that it is just behind the
sensor opening in the case.
Move lamps, vents or other sources of
abnormal temperature away from sensors
Adjust C1=XX value in installer mode to
correct perceived sensor inaccuracy. Page19
The Ho=XX &/or Co=XX value is inhibiting
heating or cooling calls. Change these values
in the installer menu, details on page 19.
Set SW2=OFF and retest heating & cooling
operation.
Sw7 sets minimum run period from 2 or 6
minutes.
Check W1 & Y1, Y2 for correct connections.
Check for 24VAC on the 24 & 24C terminals
The reversing valve remains energised after
the heating/cooling has stopped to limit de‐
compression hiss. Reversing valve will de‐
energise within 2 hours of the last call.
Exit commissioning mode before handover
to user. See page 21
LBP reached, outside air too cold for reliable
HP operation. Set LBP with the LB=XX value
in the installer menu, details on page 19
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