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Model reference

Lennox 81M28

Heat Pump

3 documents22 error codes4 service modes

Available documentation

Service Manual

  • HPXA16 Series23 pg
    Covers this model
  • XP15 Series Service Literature21 pg
    Covers this model
  • XPG20 Series Service Literature36 pg
    Covers this model
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Error codes (22)

CodeMeaning
1Long Run Time2System Pressure Trip or Discharge Sensor Fault3Short Cycling4Locked Rotor5Open Circuit6Open Start Circuit7Open Run Circuit8Welded Contactor9Low VoltageAlternating FAST Flash (Green/Red)Coil sensor problemAlternating SLOW Flash (Green/Red)5-minute anti-short cycle delay after initial power up, safety trip, or end of…Green FAST Flash / Red OFFDischarge sensor lockout (5 strikes)Green FAST Flash / Red ONDischarge line temperature lockout (5 strikes)Green OFF / Red FAST FlashDischarge sensor faultGreen OFF / Red SLOW FlashLow pressure faultGreen ON / Red OFFLow pressure lockout (5 strikes)Green ON / Red ONCircuit board failureGreen SLOW Flash / Red OFFHigh pressure faultGreen SLOW Flash / Red ONDischarge line temperature faultOFF/OFFNo power (24V) to board terminals R & C or board failure.Simultaneous FAST Flash (Green/Red)Ambient sensor problemSimultaneous SLOW Flash (Green/Red)Normal operation

Service modes (4)

  • Compressor Modulation Operational Check["Turn main power OFF to outdoor unit.","Adjust room thermostat set point above (heating) or below…
  • Compressor Two-Stage Modulation Operational Check["Turn main power OFF to outdoor unit.","Adjust room thermostat set point above (heating) or below…
  • Defrost Board Test Mode["Ensure Y1 input is active (ON) and O line is inactive.","Apply 24V power to the defrost control…
  • LSOM Installation Verification Test["Test 1 (Trip LED)

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