CH on heats HW, and HW on heats CH (Ed.)

[Shimlasun]

Not fully sure as it’s my mother in laws boiler but she thinks it started up with the new controller (installed only as old one was outside in a garage with boiler). I don’t think there’s a manual valve, she’s never had to adjust any valve to switch btw HW / CH ..

 

[JohnD]

There is no cylinder stat visible

https://www.screwfix.com/c/heating-plumbing/cylinder-thermostats/cat831450?cm_sp=managedredirect-_-plumbing-_-cylinderthermostat

And OP can't see a motorised valve

https://www.screwfix.com/search?search=Port+valve&brand=drayton|flomasta|honeywell_home|worcester_bosch

So perhaps it was built with gravity HW

There might be a cyltrol or similar on the cylinder return.

They are still available but very expensive.

I used to have one but converted to fully pumped which was better.

 

[Shimlasun]

Thank you. Is the cyltrol another way of switching btw supplying CH and HW… if we don’t have a motorised or manual valve? Just trying to understand as much as I’m able to!

Is there any chance this is the controller being installed incorrectly (wired badly) if it’s been an issue since then? My mother in law hasn’t been able to get the chap who installed it to take a look (not answering messages) and we’re just not sure whether to now get an electrician to look at the wiring of the controller, or a heat engineer to look at all the valves/system.

 

[terryplumb]

Engage a heating engineer.

 

[RandomGrinch]

It’s 2 Zone A27-HW. I’ve just asked, she’s not entirely sure but thinks it has been doing this since around the controller was installed. “It’s never been right”. Do you think that means it might be the controller not installed correctly?

If (and this is the big question) you do have a gravity system, the HW should be independently controlled.
However, if central heating is called for, the heating and hot water will come on together. This is normal behaviour.

What's interesting, is the A27-HW doesn't have an option for allowing this behaviour - it doesn't have a 'Gravity' mode.

If you are comfortable, with the power to the controller safely isolated, could we have a photo of the wiring behind the A27-HW?

 

[Shimlasun]

Ok thanks. Just to add, thanks for changing my post title, but when the HW is heating, the CH doesn’t come on a littke bit, it comes on full blast and doesn’t switch off when the thermostat reaches target temp, because of course the HW wouldn’t be linked to the thermostat. So it overshoots and gets the house very warm. It’s very odd!

 

[JohnD]

A cyltrol is a thermostatic valve that stops the boiler heating the cylinder once the cylinder is fully heated. There is also Drayton equivalent. I had one in a very old installation. If you photograph the pipe near the bottom of the cylinder, that goes to the boiler, we might see it.

Mine was 30 years old and jammed. I bought a replacement but didn't use it as there is a better way. I think I eventually sold it on ebay for about £130.

I found an even older brass valve under the floor, winter/summer, to manually control the radiators or cylinder.

 

[Shimlasun]

If (and this is the big question) you do have a gravity system, the HW should be independently controlled.
However, if central heating is called for, the heating and hot water will come on together. This is normal behaviour.

What's interesting, is the A27-HW doesn't have an option for allowing this behaviour - it doesn't have a 'Gravity' mode.

If you are comfortable, with the power to the controller safely isolated, could we have a photo of the wiring behind the A27-HW?

Thank you, that’s interesting, I wonder how we can figure out if it’s a gravity boiler… yes we’ll have a go at taking the photo, would you mind taking a look if we send in the morning … I don’t think I can manage that one myself

 

[Shimlasun]

A cyltrol is a thermostatic valve that stops the boiler heating the cylinder once the cylinder is fully heated. There is also Drayton equivalent. I had one in a very old installation. If you photograph the pipe near the bottom of the cylinder, that goes to the boiler, we might see it.

Mine was 30 years old and jammed. I bought a replacement but didn't use it as there is a better way. I think I eventually sold it on ebay for about £130.

I found an even older brass valve under the floor, winter/summer, to manually control the radiators or cylinder.

Thanks for explaining had a look around can’t see anything like that… here’s a picture of the pipes at the bottom of the cylinder. Wow £130 eeek! Hope it’s not one of those!