Potterton Promax HE Plus / S Plan / Nest wiring

[grahamgibson]

Hi,

I'm in the process of fitting Nest for my mother-in-law and tidying up some very messy wiring at the same time. Standard S Plan layout with Potterton Promax HE Plus boiler.

Currently, the live supply to the wiring centre comes from the load side of the 3A FCU and then there are permanent live and switched live feeds to the boiler as expected. However, there is also a 230V output terminal at the boiler, which is not currently used, but which the manual states can be used to power an external control e.g. thermostat or programmer.

My question is - is is essential to use this 230V output from the boiler as the live feed to the wiring centre (and hence all of the other central heating controls), or is it ok as is i.e. where the live feed to the wiring centre comes from the load side of the 3A FCU? I could reconfigure this if necessary, but not sure if it is essential. The system has been working ok for years.

Hope this is clear and thanks for any expert assistance!

Cheers,
Graham

 

[ianmcd]

what existing programmer do you have

 

[Deleted member 267285]

If it’s not broke don’t fix it. I’d say all is fine to leave if it’s been working for years.

 

[grahamgibson]

Honeywell ST9120C. Replacing with Nest is a doddle, but was checking all the rest of the wiring at the same time, so wanted to make sure.

 

[ianmcd]

well if all was working before just leave it as it is, no need to take the external controls feed from the boiler terminals