Neat 3rd Gen and Worcester Greenstar 40CDi

[neilfearnley]

Hello,

I have just had installed a Nest 3rd Gen thermostat so I can control my heat remotely, on my 12 year old Worcester Bosch 40CDi Combi Boiler.

Everything appears to be working just fine apart from it seems the heating pump runs continuously 24/7.  Im pretty sure this should not happen, so wondering if anyone can shed some light on how I fix this issue as my friend who installed it is also unsure how to fix this. 

many thanks for any advice in advance.

Neil

[Frustratedddd]

That sounds like a bit of an issue, as the thermostat is the part that turns the pump on/off! Certainly should not run 24hr, that defeats the object of having a thermostat. That means it's not wired correctly by the sounds of things.

For it to run 24hr means you have no switching, and would assume the installer has connected live neutral direct to the pump!!

What happens when you turn the stat from calling for heat and not calling? The pump still runs?

Can you upload a picture of the Heat Link wiring, and perhaps we can go from there.

[neilfearnley]

Hello. I will indeed get some photos of the wiring to post tomorrow. But just so you know the boiler does not fire up, when the nest reaches temp the boiler isnt firing, its just the pump stays on 24/7. The boiler will only fire when we need heat.

[Frustratedddd]

Well I am totally confused!

You say ''Everything appears to be working just fine apart from it seems the heating pump runs continuously 24/7'' Now you are saying '' the boiler does not fire up, when the nest reaches temp the boiler isnt firing'', so which part is working just fine?

That means to me nothing is working correctly!

What system do you have and did you follow the installation wiring diagram for your system?

[neilfearnley]

Hello. It was done by a local plumber, but he wasnt seemingly too good with Nest. prior to this I had a Worcester digital room stat on my wall, connected to the boiler. Timer functions were all handles by a TP200 unit that plugs into the front of the boiler. I had absolutely no issues with it, apart from I was not able to connect remotely and turn heating on/off while out of the home. The only thing that has changed is the installation of the Nest 3rd Gen, so I think I am fair to assume something is wrong there. Ill get some pictures of wiring soon as I am back near the boiler.

[neilfearnley]

Wiring pics:-

https://www.dropbox.com/scl/fo/zyot0apssrn22gip76niv/h?rlkey=l9ycp64qixkhjkxyfntvrfhr2&dl=0

[AlexD]

Thank you for the pictures. Just to confirm, as the wires are very long and only 2 colours, you have 2 wires in T1/T2 that go from there to the thermostat display, 2 wires in N/L that are neutral and high voltage live wire and 2 wires in terminals 2 and 3. The one in terminal 2 being high voltage (or low voltage wire if you have a low voltage/dry contact boiler) and the call for heat wire in terminal 3, correct? 

[neilfearnley]

That is correct yes

[TudorL]

Hi there @neilfearnley and thanks for reaching our Community. I'm sorry to hear about this, but I'll do my best to help you out. It's best to start from a picture of the wiring done on the Heat Link, as @Frustratedddd suggested. 

[neilfearnley]

I will get some pictures soon as I am back near the boiler. Many thanks

[TudorL]

No worries, keep us posted.

[neilfearnley]

Good morning all,

please see pictures of the wiring on this link:-

https://www.dropbox.com/scl/fo/zyot0apssrn22gip76niv/h?rlkey=l9ycp64qixkhjkxyfntvrfhr2&dl=0

Hope this will help

Neil

[neilfearnley]

Apparently it may not be the pump thats running. my guy says its coming from the top of the boiler, behind the units in the picture? Any help?

https://www.dropbox.com/scl/fi/t2c8bn323wn2y7wkba50f/image0.jpeg?rlkey=fyk50vdmvh46erhy108r4t8du&dl=...

[Frustratedddd]

Does terminal ''3'' at the Heat Link go to terminal Lr at the boiler?

Are Terminals ''Live & Terminal 2'' both just Live, coming from the boiler?

[neilfearnley]

Hello, from my sparky:-

Terminal 3 (n/o) does go to Le at the boiler. Terminal 2 (com) is perm feed but from Ls at the boiler

[Frustratedddd]

Where is Le and what does that do?

[neilfearnley]

From Sparky….

Le??? I don't think there is an Le.
Boiler controls are as follows:
NS - neutral supply
LS - live supply
LR - live return (no/nc).

[Frustratedddd]

You wrote it!

Terminal 3 (n/o) does go to Le at the boiler. Terminal 2 (com) is perm feed but from Ls at the boiler

[neilfearnley]

Let me get sparkys reply 🙈 sorry. Give me 10

[neilfearnley]

Apologies it was my typo.

should have read:-

Terminal 3 (n/o) does go to Lr at the boiler.
Terminal 2 (com) is perm feed but from Ls at the boiler.

[Frustratedddd]

I think we need to go back to the start of your issue.

1. Can you confirm, when calling for heat, ie the thermostat shows orange at the display, does the central heating pump run and the radiators get hot?

2. When the thermostat is not calling for heat, display goes black, does the pump shut off?

3. Does the heating system work like it use to do other than the noise you can hear?

I think the wiring sounds ok, except one crucial wire is missing, and thats the Earth wire!! That’s the most important wire, the others just make the item work!!

You need to check these things before you go any further,

The noise I think your hearing is the boiler fan, and because it’s an older boiler could be showing its age hence the noise.

When you first asked the question of a noise, you stated pump. I think this might have misled the situation.

[neilfearnley]

I agree I probably did mislead a little with pump. The reason was I can hear the boiler at night so assumed it was the pump. So lets start again.........

Everything works as it should on the nest. The gas fires up when heating is called (display goes orange), and the heat works ok. Hot water is fine from the boiler too. When the display goes black my assumption is that the gas goes off (it does) and after a short while the boiler goes into sleep. With my previous thermostat everything was dead silent. My sparky took the cover off the boiler today and he said the pumps are not working, but he thinks some sort of fan at the very top back of the boiler is what is continuing to run and make the noise. Is there an exhaust fan there maybe? What causes this to go on/off as potentially thats what seems to be making the noise. 

Apologies for the confusing messages.

Neil

[Frustratedddd]

OK, first thing is yes a fan is located at the flue. I would suggest try turning the boiler supply off at the main for 5-10 mins, and see if that sorts the fan out. Failing that, a boiler service person should give it a once over. Could be the pressure switch sticking.

Easy way to prove pump running or not is, feel nearest radiator, and when you call for heat that should feel warm one end. Anyway if your heating is working, then the pump is running.

I don’t think anything’s wrong with the system it’s the fan that is confusing the issue.

[neilfearnley]

Thank you. I have a plumber friend who has experience of Nest popping in tomorrow now to take a look. Ill post his findings tomorrow when he has been

[AlexD]

Thanks for keeping us posted here with all the details. Make sure to let us know how it goes. If your plumber friend needs any assistance on the Heat Link or thermostat side they can reach out to us directly at +44(0) 808 169 2307 - available 0800 - 1900 GMT Monday to Friday and 0900 - 1700 Saturday and Sunday and my colleagues can assist with anything live. 

[Vladut]

Hi there, just checking in with you. Did you manage to check the last message my colleague sent?

[neilfearnley]

I did I am just waiting for my plumber to attend then ill post the issue he found (if any)

Neil 

[TudorL]

Got it, no worries. Keep us posted! 

[neilfearnley]

Its looking like its not the heating pump running. Is there a fan at the top of the boiler, it could be this that is permanently running. I just assumed was the heating pump but appears not to be the case. The unit running is at the very top of the boiler.

[neilfearnley]

Hello Everyone,

so I had my plumber out yesterday to take a look for me, Though also not sure, he said its actually is certainly the circulation pump not the gas fan I have suggested above. So lets work on that basis now. He said the main boiler board has a timer on it so the circulation pump shuts down after an amount of time. Unfortunately mine does not, its just permanently on. He seems to think there is a fault on the main boiler circuit board causing this.

From my perspective its very strange this only happened once the Nest was installed. Due to my boiler being 13 years old, he actually suggested might be worth changing the whole boiler rather than fix this one.

I guess my only option right now is to try and source a board online and give that a go. I seem to be able to get a board off ebay for about £60, so might be worth a try.

Any thoughts?

Neil

[Frustratedddd]

Silly question, but why did you not get the plumber to fix the issue when they were there? Another question, why not get the person that fitted the thermostat to come back?

Much easier on site than surmise a problem!

[neilfearnley]

Hello. So the guy who fitted the Nest did come back but he just didnt know what was wrong hence why I got the plumber in. The plumber believes its the main board in the boiler, in particular the timing part of it to switch pump off.  For him to fix that meant a new board which he did not have. So yes i do have that option to purchase a new board and get him back, but it all seems a coincidence this problem only occurrd once Nest was installed, prior to that we were all good.

Neil

[Frustratedddd]

Something doesn’t sound right as the thermostat has all the ability to turn the pump on/off. All the thermostat does is act as a thermal switch, which means put that in the circuit of the pump, and that switches the pump.

I think you need to get a Nest pro to sort your issue out, then you have a backup if anything is installed incorrectly. Having a new board fitted may not be the problem if working before. 

[neilfearnley]

But surely the boilers main board will control that timing of the pump going on and off? Not the Nest? Wouldnt Nest just demand the boiler fire, or stop and nothing else?

Wasnt aware there was Nest Pro's about to be honest. Ill have to Google one.

Neil

[Frustratedddd]

That depends how the install has been done.

The Nest can operate everything for your heating and water on it's own, as it's a programmer as well. The Heat Link does all the switching for both Heating and water if just used on it's own. For example, I have a 2 x 3kw electric fires in my garage run from a Heat Link via a contactor, all run via the Nest schedule. Not what it's designed to do, but works a treat. You will be suprised how versatile the Nest can be if installed by a good electrician.

You said yourself the system was working all fine until the Nest was installed, so why wouldn't it now unless an incorrect install, or damage on the install?

Nest Pro is shown in settings if installed by one of them, yours I assume has not been installed by a Pro.

https://nest.com/uk/nest-pro-installation/

[neilfearnley]

No it was just installed by a regular sparky. Ill speak to a Nest Pro engineer I think then and go from there, but yes I tend to agree with you, as all was working fine before. If not then it would seem on face of it the sparky has done something to damage that timing circuit on the main board

[Frustratedddd]

Technically speaking, you should be able to remove all the electrical programmer parts from the boiler and just use the Nest to control everything.

The trouble you have, is finding out what is exactly going on at present by a good electrician. This needs to be done on site, otherwise you will be so confused with information given on here.

[neilfearnley]

Yes understand. But I believe everything on the boiler is controlled by the main mother board. The boiler does have a TP200 timer installed in the front of the boiler however there is no timer set on it and doesnt appear to be affecting anything. All the programming is being done via the Nest app and all seems to be working fine. Its literally just the continual running on the circulation pump which must surely be controlled by the main mother board on the boiler not the Nest, as the Nest is switching the gas supply on and off as it should no problem.