Central heating valve issue?

[FcB]

Hi
I have a gas boiler (not a combi) and a Nest thermostat.
The issue I have is the heating is coming on as scheduled but once the room is at temperature the heating does not turn off.
The hot water appears to be stuck to heat also as this is running all day.
Nest have ruled out an issue with the thermostat.
Everything seems to indicate there is an issue with the valve.
Basically, I’d like to know if there is a DIY fix for this and what the name of the valve would be please?
Thanks!!

 

[sxturbo]

i assume you have a 3 way valve in the system?

i presume the hot water is scheduled to be on all day?

 

[FcB]

The hot water is not scheduled to be on all day. Just an hour in the morning and at night.

It is a 3 port valve if that helps at all?

 

[sxturbo]

The hot water is not scheduled to be on all day. Just an hour in the morning and at night.

It is a 3 port valve if that helps at all?

so does the heating ever switch off? or the hot water ever switch off?

i suspect its the 3 port valve at fault, either sludged up, or faulty motor top.

 

[FcB]

Nope that’s my issue, I have to manually switch the boiler off at the wall to cut it out. When I switch it back on the hot water is on heat and the central heating fires up as per the thermostat temp.
We had the system power flushed a year ago due to sludge. Do you think it could still be the issue with that in mind?

what is the motor top? Are the valve/motor top issues that I can resolve myself DIY-wise?

Thanks for your help so far

 

[terryplumb]

Replace the mid position valve .

 

[sxturbo]

did the issue only start once the nest was installed, or has it happened since?

 

[FcB]

Best has been fitted for some time now. The issue started recently following having a radiator moved

 

[FcB]

@terryplumb
Is that a job I could do myself or does it require a professional?

 

[terryplumb]

Depends on what your skills are I suppose. Changing the actuator head is fairly simple on most makes,simple re wiring. If the whole valve needs changing that requires working on the plumbing also .....
Are you up for it ??
Posting a pic of the valve would be helpful

 

[sxturbo]

as terry said, it will be the 3 way valve then.

most of the time you can get away with just replacing the head, sometimes however you need to replace the valve aswell. however seeing as you recently had a system clean the valve should be stuck with sludge

 

[ericmark]

It seems likely a micro switch in the valve head has failed or stuck in, it is not really an option to renew the soldered in V3 micro switch, you would normally replace the whole head because of the complex internal wiring it is not easy to test, the 5 wires have a reasonable universal colour code so I suppose you could DIY the swap, and if same make as original often the valve and head clip together so you can change head and leave the valve plumbed in. It is 230 volt so of course need to ensure dead before working on it.

 

[FcB]

Thank you all for your replies. I think this one may be over my head!! I’ll give most things a try but won’t play about with wiring etc.

Here is a pic of the valve in case that helps at all?

 

[terryplumb]

Thats a Drayton valve. The white actuator head just clips off the brass body ,no plumbing work to do . A replacement just clicks into place. It comes pre wired cable attached already. You could unclip it ,make sure the spindle moves freely in the brass body. If it does, then fit a new actuator .

 

[FcB]

Thanks Terry!
Sorry if I’m missing something but what is the actuator please?