Radiators Not Heating — Whole House or Just Some

Failed circulating pump

The pump drives hot water around the system. If it fails, water doesn't circulate and radiators stay cold even though the boiler fires.

Failed zone valve

S-plan and Y-plan systems use motorised valves to control flow to heating and hot water zones. A seized zone valve can cut off an entire zone.

TRVs all closed or seized

If all thermostatic radiator valves are turned to zero or have seized shut, no radiator will heat even though the boiler and pump work.

Boiler lockout

If the boiler has gone into lockout, it won't produce heat. Check the display for a fault code.

Practical checks and next steps

There are a few quick checks you can do — but if your radiators aren't heating, a qualified engineer is almost always needed to diagnose and fix the cause.

• Check the boiler display for a fault code — look this up for your model.
• Check the boiler pressure gauge — repressurise if below 1 bar.
• Check that zone valves and the programmer are calling for heat.
• Feel the boiler flow pipe — if warm, the boiler is firing but circulation is failing.
• Check TRV settings on radiators — ensure none are turned to zero.
• Call a heating engineer if you can't identify an obvious cause.