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Air source heat pump circuit not operational

Air Source Heat Pumps (ASHPs)

Last Post by Mars 10 months ago

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Plummersknowe

(@plummersknowe)

Active Member Member

Joined: 12 months ago

Posts: 6

Topic starter 05/01/2026 8:07 pm [#2711]

Hi - need some advice about one circuit on my heating system - it’s an air source heat pump which is working correctly heating every circuit except for one which despite reprogramming and resetting the wireless thermostat it is failing to accept heat. The Neostat V2 is indicating it has a wireless connection to the Heatmiser hub and has the flame icon showing that it is responding to the low temperature - room is now at external ambient temperature. Thinking it may be an airlock - anyone able to diagnose & advise on how to resolve. Many thanks

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Mars

(@editor)

Illustrious Member Admin

Joined: 6 years ago

Posts: 4958

06/01/2026 10:08 pm

Welcome to the forums.

If the thermostat shows it’s calling for heat but that circuit isn’t warming up, an airlock could definitely be the culprit, especially if the rest of the system is working fine. Bleeding the radiators or the circuit to remove trapped air is a good first step. That’s easier said than done (from our recent experience) unless you have a flush and fill valve installed.

Also, check that the motorised valve or zone valve for that circuit is actually opening properly. A couple of years ago the motor on our Honeywell valve leading to the UFH was fried. If it’s stuck or faulty, heat won’t flow even if the thermostat signals for it. If you’re comfortable, try manually operating the valve to see if it moves. Otherwise, a heating engineer can help diagnose and fix valve or circulation issues.

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