E20
Rheem
Communication Error Between Main PCB and Remote Controller
Rheem tankless water heater shows E20 and will not operate
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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
Damaged remote controller cable, Incorrect wiring polarity, Faulty remote controller, Faulty main control board communication circuit
How to Fix / Troubleshooting
Safety first: Turn OFF power before working on low-voltage wiring.
- Check cable routing: Inspect the cable between the heater and remote controller for cuts, staples through the wire, or tight bends.
- Verify connections: Ensure the remote cable is connected to the correct terminals on both the heater and remote. Observe polarity if specified.
- Test without remote: Disconnect the remote controller and try operating the unit using the onboard controls (if available). If the unit works, the remote or cable is faulty.
- Replace components as needed: Replace the remote controller cable first, then the remote itself if E20 remains. If still present, the main control board may need replacement.
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Repair Difficulty
Medium
3/5
Required Part
Remote Controller Cable
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