Nest 3rd Gen with Worcester 40CDi - Pump always on

[charliefunkuk]

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

 

[stem]

I'm assuming you are referring to the circulation pump located inside the boiler.

If so, that pump is controlled by the boiler's internal circuits and not the Nest.

All Nest does is tell the boiler that heat is required which you say it is doing. Then the PCB inside the boiler then looks after all of the boiler's internal functions. Diverter / Gas Valve / Ignition / Pump / etc.,

Are there any other external controls fitted to the boiler? Frost Thermostat? Weather Compensation etc.,

Maybe one of the RGI's on here who is familiar with the intricacies of your particular boiler and has come across this before maybe able to assist.

 

[ianmcd]

can you post a pic of the wiring both at the nest end and the boiler end

 

[charliefunkuk]

I'm assuming you are referring to the circulation pump located inside the boiler.

View attachment 324917


If so, that pump is controlled by the boiler's internal circuits and not the Nest.

All Nest does is tell the boiler that heat is required which you say it is doing. Then the PCB inside the boiler then looks after all of the boiler's internal functions. Diverter / Gas Valve / Ignition / Pump / etc.,

Are there any other external controls fitted to the boiler? Frost Thermostat? Weather Compensation etc.,

Maybe one of the RGI's on here who is familiar with the intricacies of your particular boiler and has come across this before maybe able to assist.

Thanks for the reply. There is a TP200 timer on the front of the boiler, which obviously i am no longer using or is the original worcester room stat now connected to it.

And yes its the circulation pump thats running all night thats my issue.

Neil

 

[stem]

The TP200 will only switch the heating on/off so again won't directly control the pump. If you do as suggested by @ianmcd and post a couple of photos it might help us spot something.

 

[charliefunkuk]

Ok will get some pictures and post. Thank you so much

 

[charliefunkuk]

 

[charliefunkuk]

This is wiring