Boiler won't fire up when heating activated but does with hot water.

[Nhaigh90]

I have a worcester greenstar camray utility 12/18 oil boiler paired with Potterton EP2 programmer. When heating is activated the boiler won't fire up but does fire up when hot water is activated. I have got around this problem by locking open the honeywell motorized valve so as when the hot water is on it also heats the rads in the house. I have a spare programmer which I switched in and the same problem persists. Any ideas what else to check? Tia

 

[ShaunCorbs]

Port valve probably

 

[Corgisince1974]

I have a worcester greenstar camray utility 12/18 oil boiler paired with Potterton EP2 programmer. When heating is activated the boiler won't fire up but does fire up when hot water is activated. I have got around this problem by locking open the honeywell motorized valve so as when the hot water is on it also heats the rads in the house. I have a spare programmer which I switched in and the same problem persists. Any ideas what else to check? Tia

Is the room thermostat set above the room temperature? With all the hot weather that we’ve been your house must be hot enough already surely. If it’s not the room stat then it’s the motorised valve or loose wiring.

 

[BigSid]

I had the exact same problem about 5 years ago. It was the motorised valve.

 

[littlespark]

Agree.

Most probably the motorised valve.
The head comes off the valve, so no draining down of the system required, but you may need an electrician or heating engineer to wire in the new head.

To test it, you could try LIGHTLY tapping the valve with a hammer when it’s calling for heat… it might loosen the head enough to open.
Only when the valve is fully open, that the little switch inside operate to trigger the boiler