Page 36
XP21
Table 12. Compressor Fault and Alarm LED Codes and Related icomfortt Thermostat Alert Codes
NOTE See notes 1 and 2 in table below for duration of fast / slow flashes and pause.
Heat Pump Control
LEDs
icomfortt
Thermostat
Display
Condition
Possible
Cause(s)
Solution
Clearing Sta-
tus
DS15
Yellow
DS13
Red
Off On
Moderate/
Critical
3
Alert
Code 400
Compressor
internal
overload trip
Thermostat
demand signal
Y1 is present, but
compressor not
running
1
Compressor protector is open.
Check for high head pressure
Check compressor supply voltage
2
Outdoor unit power disconnect is open.
3
Compressor circuit breaker or fuse(s) is open.
4
Broken wire or connector is not making contact.
5
Low or high pressure switch open if present in
the system.
6
Compressor contactor has failed to close.
Clears the error
after current is
sensed in the
run and start
winding for two
seconds, ser-
vice removed or
power reset.
1 flash
then
pause
Off
Critical Alert
Code 401 on
outdoor
controls
101796−01
through −04.
Moderate
Alert Code
401 on
101796−04
and later
Long run
time.
Compressor is
running extreme-
ly long run
cycles.
1
Low refrigerant charge.
2
Evaporator blower is not running.
Check blower relay coil and contacts
Check blower motor capacitor
Check blower motor for failure or blockage
Check evaporator blower wiring and connec-
tors
Check indoor blower control
Check thermostat wiring for open circuit
3
Evaporator coil is frozen.
Check for low suction pressure
Check for excessively low thermostat setting
Check evaporator airflow (coil blockages or re-
turn air filter)
Check ductwork or registers for blockage.
4
Faulty metering device.
Check TXV bulb installation (size, location and
contact)
Check if TXV/fixed orifice is stuck closed or de-
fective
5
Condenser coil is dirty
.
6
Liquid line restriction (filter drier blocked if pres-
ent)
.
7
Thermostat is malfunctioning
.
Check thermostat sub−base or wiring for short
circuit
Check thermostat installation (location and
level)
Clears the error
after 30 consec-
utive normal run
cycles, or after
power reset.
2 flashes
then
pause
Off
Critical Alert
Code 402
System
pressure trip
Indicates the
compressor
protector is open
or missing supply
power to the
compressor.
1
High head pressure.
Check high pressure switch if present in sys-
tem
Check if system is overcharged with refriger-
ant
Check for non−condensable in system
2
Condenser coil poor air circulation (dirty,
blocked, damaged).
3
Condenser fan is not running.
Check fan capacitor
Check fan wiring and connectors
Check fan motor for failure or blockage
4
Return air duct has substantial leakage.
Clears after four
consecutive
normal com-
pressor run
cycles, or after
power reset.
3 flashes
then
pause
Off
Moderate
Alert Code
403
Short cycling
Compressor is
running less than
three minutes.
1
Thermostat demand signal is intermittent.
2
Time delay relay or heat pump control is defec-
tive.
3
If high pressure switch is present, see flash code
2 information.
Clears after four
consecutive
normal com-
pressor run
cycles, or after
power reset.
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