What It Means
High line voltage feed to outdoor unit above safe range.
Rheem AC & Heat Pump
Rheem AC & Heat Pump Error Code 28
Troubleshooting guide for the Rheem AC & Heat Pump system fault 28.
Possible Causes
- Utility supply voltage surge.
- Incorrect electrical service supply.
- Transformer tap misconfiguration.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
High line voltage fault.
All Recorded Causes
Supply voltage above allowable range, incorrect electrical service, transformer/tap issue, or utility voltage problem. Verify voltage at the disconnect and unit.
Verify Before Replacing Parts
- Confirm the exact Rheem model family and ac and heat pump context before acting on a generic code description.
- Start with line voltage, low voltage, and board output checks in sequence so the fault is isolated cleanly — the data plate flags supply voltage above allowable range, incorrect electrical service, transformer/tap issue,….
- Inspect connectors, relay outputs, and any recently replaced electrical parts for mismatch or loose fit, and verify verify voltage at the disconnect and unit.
- After the correction, run the system long enough to confirm the ac and heat pump fault does not return under normal load.
Not sure which system this Rheem code is on?
ACLogics has guided diagnostics for 57 Rheem fault codes and asks the right questions to narrow it down.
