Nest Install - Centrifugal Pump Question

[seb9]

Hi all,

Another Nest install question which I'm sure you're all sick of!

We have a Worcester Greenstar 30si boiler and a sauermann si82 centrifugal pump. There is a safety switch coming from the pump which has been wired up to the boiler Ls and LR. The nest has been wired up but only works when the safety cable is removed from the boiler. It's obviously there for a reason so left it as is.

Any ideas why this is the case or what the work around is?

Cheers

 

[ianmcd]

your boiler if you have the model correct is a combi boiler so why do you have an external pump ?

 

[JonathanM]

your boiler if you have the model correct is a combi boiler so why do you have an external pump ?

Is it a condensate pump?

 

[stem]

It is a condensate pump. The safety switch should be wired in series with the switched live supply to the boiler so that it stops the boiler running when the safety switch operates.

The diagram below is from the manufacturers website here. There is also some additional information.

So for Nest 3rd Gen that would equate to:

From the way that it was wired before I'm guessing that you didn't have a room thermostat connected to Ls and Lr.