Lennox Signature XP21 Series Installation And Service Procedure page 36

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
icomfortt
LEDs
Thermostat
DS15 DS13
Display
Yellow Red
Moderate/
Off On Critical
Code 400
Critical Alert
Code 401 on
outdoor
controls
101796−01
1 flash
through −04.
then
Off
pause
Moderate
Alert Code
401 on
101796−04
and later
2 flashes
Critical Alert
then Off
Code 402
pause
3 flashes Moderate
then Alert Code
Off
pause 403
XP21
Possible
Condition
Cause(s)
Thermostat
Compressor
demand signal
3
Alert internal Y1 is present, but
overload trip
compressor not
running
Compressor is
Long run running extreme-
time.
ly long run
cycles.
Indicates the
compressor
System
protector is open
pressure trip
or missing supply
power to the
compressor.
Compressor is
running less than
Short cycling
three minutes.
Solution
1
Compressor protector is open.
S
Check for high head pressure
S
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.
1
Low refrigerant charge.
2
Evaporator blower is not running.
S
Check blower relay coil and contacts
S
Check blower motor capacitor
S
Check blower motor for failure or blockage
S
Check evaporator blower wiring and connec-
tors
S
Check indoor blower control
S
Check thermostat wiring for open circuit
3
Evaporator coil is frozen.
S
Check for low suction pressure
S
Check for excessively low thermostat setting
S
Check evaporator airflow (coil blockages or re-
turn air filter)
S
Check ductwork or registers for blockage.
4
Faulty metering device.
S
Check TXV bulb installation (size, location and
contact)
S
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
S
Check thermostat sub−base or wiring for short
circuit
S
Check thermostat installation (location and
level)
1
High head pressure.
S
Check high pressure switch if present in sys-
tem
S
Check if system is overcharged with refriger-
ant
S
Check for non−condensable in system
2
Condenser coil poor air circulation (dirty,
blocked, damaged).
3
Condenser fan is not running.
S
Check fan capacitor
S
Check fan wiring and connectors
S
Check fan motor for failure or blockage
4
Return air duct has substantial leakage.
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.
Page 36
Clearing Sta-
tus
Clears the error
after current is
sensed in the
run and start
winding for two
seconds, ser-
vice removed or
power reset.
Clears the error
after 30 consec-
utive normal run
cycles, or after
power reset.
.
Clears after four
consecutive
normal com-
pressor run
cycles, or after
power reset.
Clears after four
consecutive
normal com-
pressor run
cycles, or after
power reset.