Heatmiser Insufficient Heat Output / Flow Issue

Underfloor heating controlled by Heatmiser thermostat is slow to warm up or never reaches setpoint

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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

Manifold flow temperature too low, Air in UFH loops, Closed or incorrectly balanced manifold valves, Incorrect floor sensor limit too low

How to Fix / Troubleshooting

Safety first: Any work on the manifold or boiler should be done by a competent person. Isolate power where necessary.

Steps:

  • Check the setpoint on the thermostat and ensure it is high enough for comfort.
  • Verify the maximum floor temperature limit in the thermostat settings; increase within safe limits for your floor covering.
  • Inspect the UFH manifold: ensure all relevant loop valves are open and that the pump is running when there is demand.
  • Bleed air from the UFH loops and check that the flow temperature from the boiler is appropriate (typically 35–45°C for UFH).
  • If issues persist, have a heating engineer check system design and balancing.
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Repair Difficulty

Hard 4/5
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