H5
Hayward
High-Temperature Lockout / Repeated High Limit Trips
Heater shows H5 and shuts down; may occur after running for a short period.
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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
Chronic low flow through heater, Severely scaled heat exchanger, Faulty high-limit switch, Incorrect plumbing bypass causing short-cycling
How to Fix / Troubleshooting
Safety First: Shut off power and gas. Allow the heater to cool fully before touching internal components.
- Verify system design: Confirm that the heater is plumbed according to Hayward's installation manual, with proper bypass and no dead-head conditions.
- Check filter and pump: Clean the filter and ensure the pump is sized correctly and running at the recommended speed for heater operation.
- Inspect high-limit wiring: Loose or corroded connections can cause nuisance trips. Reseat connectors on the high-limit switch and control board.
- Evaluate for scale: If the heater is older or has seen high temperatures, internal scale may be present. A professional descaling or heat exchanger replacement may be required.
- Reset and monitor: After corrections, restore power and gas, reset the heater, and monitor operation. If H5 recurs, contact a qualified technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Heat Exchanger
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