Nest & Potteron Promax HE Store

[harrison8]

I wanted to install a 3rd gen Nest thermostat and I've run into a slight issue with the complexity of the wiring of my Potterton Promax HE Store.

It's got the programmer (A Horstmann CentaurPlus C27B) "built-in" to the boiler along side the control board which can control hot water and central heating. Outside of the boiler, there's a Potterton PRT2 manual thermostat on the wall for just the central heating.

Here's a pic of the control board;

And the programmer next to it;

The PRT2 is wired up as follows;

And the terminal block wiring diagram on the back plate of the control board;


So, terminal 1 (grey cable) goes to 5 (N) on PRT2.
Terminal 2 (black) goes to 3 (H).
Brown live goes to 2 (COM) and there's a bridge between that and 4.

As best I can tell from the Nest's own wiring diagram;



Terminal 1, grey cable, goes to N.
Terminal 2, black cable, switched live or call for heat, so that goes to 3.
Brown live goes to L. And then according to the nest manual I can bridge L & 2 since it operates a mains voltage.

If I've got that totally wrong please do give me a slap and correct me so I don't blow something up.

Edit: Hot water too much hassle, can't be bothered to try and figure it out.

 

[harrison8]

Edit: ignore this post.

 

[harrison8]

OK so I'm not going to bother wiring it up for hot water, assuming it was even possible. I don't need it, I just thought it'd be a bonus if I got that connected to the Nest. I'll just have CH connected to it. Perhaps someone could confirm if I've got the CH wiring correct though just in case. Thanks.

 

[ianmcd]

yes you are correct, you are basically using the nest as an external room thermostat, you will still control the HW using the boiler controls

 

[harrison8]

Cheers.