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Table 10. Alert Codes and Troubleshooting
Alert Code Priority
Condition
Applicable System
Component(s)
Alert Text Component or System Operational State
and Troubleshooting Tip
How to clear the alert code
380
Moderate /
Critical
EIM
Interlock relay failure
(IFC or AHC mode
on ly).
√ Interlock relay is energized, but input is not sensed after three
seconds.
√ There will be no heating or cooling due to this alert code – moderate
condition.
√ De-energize interlock relay and energize after ve minutes if
demand is still present – critical condi tion.
Automatically clears after
fault recovered.
381
Moderate /
Critical
EIM
Interlock relay stuck
(IFC or AHC modes
only)
√ Interlock relay continuously sensed (with relay o).
√ There is no heating and cooling operation – moderate condition.
√ After 10 minutes if event still exist it will be escalated – critical
condition.
Automatically clears 30
seconds after fault clears
382 Moderate EIM
Relay W1 failure
(IFC and AHC modes
only)
W1 relay is energized but input is not sensed after three seconds.
Automatically clears when
W1 relay input is sensed.
418 Moderate
EIM and Lennox
communicating outdoor unit
There is a faulty W
output circuit.
√ W terminal is energized while in cooling mode.
√ Possible cause may be a stuck closed relay on the control, or
something external to the control that is energizing W terminal when
it should not be ener gized.
√ Disconnect any wiring from the W terminal.
√ If 24VAC is still on the terminal, then it is a stuck relay.
√ If 24VAC disappears, then there is a need to check any of the wires
hooked up to the W terminal.
Automatically clears after
fault signal is re moved.
419 Critical
EIM and Lennox
communicating outdoor unit
The W output has re
ported more than ve
errors
√ The system will shut down the outdoor unit.
√ The W output (alert code 418) on the outdoor unit has reported more
than ve strikes.
√ Disconnect thermostat wire from W and verify there is no 24VAC on
the W.
√ If 24VAC is present, replace the outdoor control.
Automatically clears after
power recycled.
420 Critical
Lennox communicating Air
handler or EIM
The heat pump defrost
cycle has taken more
than 20 minutes to
complete
√ Defrost cycle lasts longer than 20 minutes.
√ Check heat pump operation.
√ This is applicable only in communicating indoor unit with non-
communicating heat pump.
Automatically clears when
W1 signal is re moved.
421 Critical
EIM and Lennox
communicating outdoor unit
The W output terminal
on the outdoor unit is
not wired correctly.
Voltage sensed on W output terminal when Y1 out is deactivated.
Automatically clears once
volt age is not sense on
output for pow er cycled.
594
Moderate /
Critical
EIM
Pre-coil discharge air
temperature sensor
problem (DFM mode
only). Advances from
moderate to critical af-
ter ten (10) minutes.
√ Interlock relay energized, but input not sensed after three seconds.
√ No heating and cooling operations.
√ De-energize interlock relay and re-energized ve minutes later if
demand is still present.
Alarm clears ve minutes
after fault clears.
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