Ideal boiler displays H8 and may limit output or cycle

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.

Possible Causes

Insufficient system circulation, Pump set too low, Blocked system filter, Closed or partially closed valves

Safety first: Allow system to cool before adjusting valves or touching pipework.

User checks:

Open all valves: Ensure all radiator valves and any isolation valves near the boiler are fully open.
Check system filter: If you have a magnetic filter (e.g. Ideal System Filter) on the return pipe, ensure its isolation valves are open. Do not dismantle it yourself.
Bleed radiators: Remove trapped air and top up pressure.

If H8 continues, a heating engineer should check pump speed, clean the system filter, and assess for sludge or blockages.

Medium 3/5

Central Heating Circulation Pump

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