E20
Alpha Flue Gas Temperature Too High

Furnace displays E20; unit may shut down on very cold days or after long run times.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Partially blocked flue, Undersized vent pipe, Excessive input due to incorrect gas orifice, Failed flue temperature sensor on Alpha furnace

How to Fix / Troubleshooting

Safety: High flue temperatures can indicate dangerous venting issues. Turn off the furnace and do not operate until inspected.

  • Visual vent inspection: Check the entire visible length of the flue for disconnections, crushing, or obvious blockages at terminations.
  • Check flue sensor: Locate the flue temperature sensor on the vent connector. Ensure it is firmly attached and wiring is intact.
  • Power reset: After verifying no obvious vent damage, reset power and test. If E20 returns, stop using the furnace.

Flue temperature and combustion must be checked by a licensed technician with proper instruments.

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Repair Difficulty

Professional Required 5/5

Required Part

Alpha Flue Temperature Sensor
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