Heatmiser Zone Valve / Actuator Backfeed or Sticking

Radiators or UFH zones controlled by Heatmiser thermostat are hot when they should be off, especially when other zones call for heat

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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

Stuck open thermal actuator on manifold, Incorrect wiring in Heatmiser wiring centre causing cross-calling, Shared return or bypass issues, Faulty zone valve motor

How to Fix / Troubleshooting

Safety first: Isolate electrical supply to the wiring centre and boiler before working on valves or actuators.

Steps:

  • At the Heatmiser wiring centre, verify that each thermostat is wired to the correct zone output and that no outputs are bridged unintentionally.
  • Check each manifold actuator or zone valve to ensure it closes fully when its thermostat is off; replace any that remain open.
  • Confirm that the boiler and pump are only enabled when at least one zone is calling for heat.
  • If hydraulic cross-flow is suspected, consult a heating engineer to review pipework and bypass arrangements.
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Repair Difficulty

Hard 4/5

Required Part

Heatmiser Thermal Actuator / Zone Valve
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