Adding a 2nd Zone (with another Nest thermostat)

[steevieb]

Hello,

I'm planning on adding a second zone to my CH, so I have upstairs and downstairs, both controlled by Nest thermostats. I already have the whole house on a Nest (located downstairs). I've access to the feed pipe, which goes into a T, one outlet serving upstairs and the other downstairs.

I'm going to fit two motorised valves to the pipework either side of the T - simple enough so far.

When it comes to the wiring, I've planned out the attached wiring diagram that I've modified from elsewhere. I'm confident I'm right but would like it sense checked, if that's OK...

Steve

 

[stem]

I can't see anything wrong with it, other than the earth's aren't shown going to the Heat links.

I see also, that the 'Hot Water Lr' is connected to the 'L' by a link, so is powered permanently. As your boiler is a Bosch Worcester of some variant, if that connection is for a timed hot water pre-heat facility, you could possibly use one of the Nests to provide that via terminals 5 & 6. I can't remember off the top of my head, but your boiler installation manual will inform you of its purpose.

 

[steevieb]

Thanks for the reply.

I should have mentioned, the boiler is a Vaillant ecoTEC 832 H combi, all HW is controlled by that. There's 4 wires coming from the boiler to the current Nest heat link (and the earth is connected!)

 

[stem]

OK thanks. I didn't recognise the terminal layout, probably because Vaillant seem to have a habit of changing their wiring terminals frequently. Also Vaillant's tend to have 'RT' and not 'Lr' (as used by Bosch Worcester) to indicate the terminal for connection for the wires from external controls.

All Combi's heat water on demand, but many have a pre-heat facility (Vaillant call it comfort mode) and some have the possibility for remote timed control of it.

There are a couple of clues that make me think this maybe the case with yours: Two terminals that have a wired link that can be removed is often there to allow the connection of external controls. Also, one of the terminals is marked 'Hot water Lr' (live return) which is in the same manner as the 'Rads Lr' terminal that you are using for the external control of the heating.

Anyway, like I said, your boilers installation manual will show if the feature is available or not, but if you are happy with the way it works now, then no point in changing it.

 

[ianmcd]

@stem ha ha what did you do mate before Hive and nest came out , just kidding mate you give great advice on here

 

[stem]

I know, it's getting to be a bit of an obsession....BTW have you ever seen a Vaillant with 'Lr' terminals?

 

[ianmcd]

I know, it's getting to be a bit of an obsession....BTW have you ever seen a Vaillant with 'Lr' terminals?

Nope never agree that Worcester do but as you correctly say valliant use RT , also no such a boiler as Valliant Ecotec 832 H combi, think it might be an Ecotec 832 plus but who knows