Hot water fires boiler but heating doesn't.

[ollie3686]

I have a Potterton Suprima 40 boiler controlled by a programmer which I can set HW and CH separately. Heating is also controlled by a Honeywell CM907 stat. Hot water and heating has been working fine for the last few weeks and even first thing this morning, but now heating has stopped working. Hirt water is working to schedule, and the boiler fires up - also when I pres the extra hot water hour. All ok.

The problem is heating. It's completely stopped working despite the stat Working as usual (or appearing to anyway). When heat is needed, the flame symbol comes on and I hear the little click, but there's no response from the boiler. Batteries have been changed, boiler reset but still nothing. I assume it's not the actuator as the boilers not even firing. Any ideas would be much appreciated because I am freezing!

 

[sooey]

But if the actuator isn't actuating how will the boiler know that it should fire?

 

[ollie3686]

Oh ok, so the stat sends the signal to the actuator, then the actuator signals to the boiler?

 

[sooey]

That's right.

 

[ollie3686]

Thanks sooey, think we're getting there. Playing about with the actuator (Danfoss HSA 3) and looks like it will only heat water with the lever on 'auto' and heating on 'manual'. It's a work-around so I'm happier but still not the answer. Is the actuator likely to be the issue?

 

[shaaaaaamo]

Interesting... This is exactly how my heating behaves and has done since it was installed a couple years ago according to the people I bought the house off.

Is there any scenario that this is 'normal' or should the boiler always fire up when the heating demands it?

 

[ollie3686]

This is the first time this has ever happened, I may be wrong on your syste, but I'd have thought 'auto' was fully automatic regardless of the system. Mind you - I'm not a plumber

 

[ALCPlumbing]

Interesting... This is exactly how my heating behaves and has done since it was installed a couple years ago according to the people I bought the house off.

Is there any scenario that this is 'normal' or should the boiler always fire up when the heating demands it?

Usually the boiler should fire up without the hot water on just when there is a demand for heating. If the motorised valve is manually open however you will need the hot water on to fire the boiler. Manually opening the valve will then allow heated water to you radiators. You should get it checked out. With any luck only the motor needs changing and I usually charge £90 + vat for that. However if the whole valve needs replacing that will require a drain down and will of course cost a lot more. Probably towards the £200 + vat area.

 

[ollie3686]

How would you know if it's the whole valve or just the motor? On auto the valve isn't moving to CH at all, only water and the mid-point. The valve isn't sticking as I've had the motor off and can even move out by hand.