E15
Alpha
Line Voltage Out of Range
Furnace shows E15; unit shuts down and may display overvoltage/undervoltage warning.
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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
Low or high supply voltage from electrical service, Loose line connections at furnace disconnect, Faulty Alpha control board voltage sensing circuit, Shared circuit with heavy loads causing voltage drop
How to Fix / Troubleshooting
Safety: Working on line voltage can be hazardous. If you are not comfortable, contact an electrician.
- Check breaker and wiring: Ensure the furnace is on a dedicated circuit and the breaker is fully engaged. Inspect visible wiring for burns or loose connections at the service switch.
- Avoid heavy shared loads: Do not run large appliances on the same circuit as the furnace.
- Power cycle: Turn off power for 5 minutes, then restore. If E15 reappears immediately, the control board's sensing circuit may be faulty.
Persistent voltage issues should be evaluated by a licensed electrician and an Alpha technician.
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Repair Difficulty
Hard
4/5
Required Part
Alpha Integrated Furnace Control Board
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