E4
Certikin
Flow Rate Below Minimum / Differential Temperature Too High
E4 error; heater may start but then shuts down quickly.
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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
Undersized circulation pump for Certikin heater, Partially closed valves, Blocked heater inlet strainer, Internal fouling of heat exchanger reducing flow
How to Fix / Troubleshooting
Safety first: Turn off power to the heater and pump before opening any pipework or strainers.
- Confirm pump size and speed: Ensure the circulation pump is correctly sized and, if variable speed, set to a speed that meets the heater’s minimum flow requirement.
- Open valves fully: Check all isolation and bypass valves around the heater and set them to provide maximum flow through the heater.
- Clean inlet strainers: Some Certikin heaters have an inlet strainer or filter; remove and clean any debris.
- Backwash filter: Perform a full backwash and rinse on the pool filter to reduce system resistance.
- Restart and monitor: Restore power and observe the heater. If E4 persists, internal scaling may be present.
Severe internal fouling of the heat exchanger requires chemical cleaning or replacement by a professional.
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Repair Difficulty
Hard
4/5
Required Part
Certikin heat exchanger / circulation pump
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