Nest Thermostat wont stop calling for heat (Y plan)

[robdupre]

@stem and @Johnmdc

Thanks for the responses all sorted and very simple issue.

For completeness, the red wire that runs to the boiler's pump live was incorrectly wired with the boilers switched live and as a result was keeping the boiler on indefinitely. Thermostat calls for heat, boiler comes on, boiler pump wire goes live (as boiler wants the pump on), thermostat stops calling for heat, but as my boiler must have pump overrun, the we are stuck in a loop where the pump overun is keeping the boiler on which in turn keeps the pump overun on.

Stupid issue, I misunderstood the role of the boiler pump wire, I thought it was a internal boiler pump (as i had with my old houses combi boiler)

Thanks again everyone, great forum much appreciated.

 

[Paulfg]

Hi there
I’m new to this site so please bare with me
After reading this post I appear to have a similar problem since I had my boiler replaced to a valiant eco tech plus and a new nest system installed
Basically the heating remains on constant until I manually select heating off and call for HW to drive the valve back to default position
I’m going to review the wiring centre and see if I can replace it with a wago L32 box
The only cable that puzzles me is a black which I suspect is coming from the boiler and connects with the live of the pump

Any suggestions as to what other core colours should come from the boiler and what their function is?

Thanks

 

[CountryFan]

How old is the boiler? 24v link left in?

 

[stem]

Hi Paulfg and welcome to the forum. Ideally you should have really started your own new thread. Posting your question on the end of someone else's thread is known as hi-jacking and is against the Forum Rules. Also, your post will only be readily obvious to contributors of the existing thread, others if they do see it generally won't scroll though a lengthy post to get to the bottom. So there will be less responses.

Unfortunately regarding the wiring colours, there is no standard colour code, they would be chosen according to the personal preferences of the original installer and what they had in their van. A couple of photos may help.

 

[Paulfg]

Apologies for hijack
Not aware of the rules but I am now

 

[Paulfg]

Is it ok to continue to post on this thread?

 

[Paulfg]

The new vanilla T boiler was installed about 2020 but I thought it may be my 3 port valve so I have put off replacing it until now
But it sounds like it may be something to do with the feeds (switched or otherwise) coming from the boiler
Didn’t want to go into the boiler wiring and thought I may be able to fix it at the wiring centre?

 

[Paulfg]

How do I start a new thread?

 

[CountryFan]

How do I start a new thread?

Go to the relevant section (plumbing and heating) and there should be an orange button that states post thread

 

[Paulfg]

Thanks for the advice

Now posted a new thread will follow up with some photos

 

[Paulfg]

I removed the boiler pump live and now the heatlink is able to stop the central heating and so far all is normal again. I do now have a dangling boiler pump wire and am not sure where it goes.

Can you please explain further how the boiler cables connect into the wiring centre on a Y plan system

 

[Paulfg]

@stem and @Johnmdc

Thanks for the responses all sorted and very simple issue.

For completeness, the red wire that runs to the boiler's pump live was incorrectly wired with the boilers switched live and as a result was keeping the boiler on indefinitely. Thermostat calls for heat, boiler comes on, boiler pump wire goes live (as boiler wants the pump on), thermostat stops calling for heat, but as my boiler must have pump overrun, the we are stuck in a loop where the pump overun is keeping the boiler on which in turn keeps the pump overun on.

Stupid issue, I misunderstood the role of the boiler pump wire, I thought it was a internal boiler pump (as i had with my old houses combi boiler)

Thanks again everyone, great forum much appreciated.

Could you please advise what type and colours of cable were used for the boiler live and switch live to and from the boiler

Thanks