Using two Nest Thermostats

[Smyles]

Hi all, I've checked all the other Nest threads, haven't found one quite like mine, so here goes...

I'm building a single room extension to my house, with underfloor heating, and I'm planning on running the heat of the exsting CH, T'd off an adjacent room.

What I want to know is, can I run two Nest stats, one replacing the existing Drayton programmable in the hallway, with a second running the UFH control for the extension, and most importantly, can the second stat "overide" the first and call for heat, when the main stat reaches target temp? Hope this makes sense, my main aim is to be able to heat the extension without a zoned system as this would be a ball ache, and I may need the extension to call for heat after the main stat reaches temp...

 

[Gaz the Sparky]

You can have more than one nest thermostat to control the heating. To zone the extension property then a new zone valve needs installing from the flowfrom theboiler. If you do it the way you have said then you won’t get heat on the new zone untill the main exsiating valve opens so it’s a pointless idea as the rest of the heating needs to be on.

So Dorito work correctly your extension pipework needs to be connected into the flow from the boiler and the 2 zone valves teed into this flow so they work independently of eachother

 

[Lower]

We have a system similar to what you describe with two nests, one controlling the main house and the other controlling the underfloor heating.

However, as Gaz the Sparky says, you can't tee it off the existing heating circuit. You need the underfloor heating to be on it's own zone with its own motorised valve so that the boiler can feed hot water to the underfloor heating, the main heating, or both at the same time.

If you did it your way the only way it could work is for the boiler to feed the both systems or the main house on its own.

 

[Smyles]

Thanks Gaz. So there's no way to get the stat in the extension (which controls the UFH circuit) to tell the stat in the hallway (which controls the boiler and existing valve) to call for heat, if the main stat has already reached temp? Creating a new zone is a pain as the extension will be difficult to pipe back to the existing valve location, hence the question.

 

[Smyles]

We have a system similar to what you describe with two nests, one controlling the main house and the other controlling the underfloor heating.

However, as Gaz the Sparky says, you can't tee it off the existing heating circuit. You need the underfloor heating to be on it's own zone with its own motorised valve so that the boiler can feed hot water to the underfloor heating, the main heating, or both at the same time.

If you did it your way the only way it could work is for the boiler to feed the both systems or the main house on its own.

Hi there, thanks for responding. Refering to your last line, I don't mind if the system overheats the rest of the house a bit while the extension comes up to temp, if the system will let me do that (i.e. the secondary stat over-rides the primary). Because the extension is UFH I think it will be more stable thermodynamically and settle down. I just worry it will come up to temp more slowly and the primary stat will cut out before it hits temp. I appreciate the correct solution is zoning, but wondered if there was anything with the Nests that would allow the scenario I've just described. Thanks agian.

 

[Lower]

If your house is anything like ours, the UFH is on at completely different times to the rest of the house. It won't be a good solution for the rest of the house to run it that way.

 

[muggles]

You do really need to take the flow & return pipes back to the primaries from the boiler. UFH takes much longer to heat up and cool down than radiators, so if you just tee off the existing system you'll find that it gets warm a couple of hours later than the rest of the house, and also remains warm after you want it to go off. You can't just put another Nest on it in the way you've described either, one will override the other

 

[Gaz the Sparky]

As said above the system wouldn’t work correctly you could wire it together and lash it up to work but the 2 nests would counter act eachother. The extension underfloor Nest would bring the boiler on and heat all the other radiators in the house. It would be better to not have the control of a second Nest and just tee into to heating and use the 1 stat for both the underfloor and house heating. This would not work effectively though as underfloor heating takes time to heat so you would be better to either not bother installing the system or plumb it in correctly and take it back to the boiler/ airing cupboard where the existing zone valves are.

 

[Smyles]

Thanks for all the feedback guys, I guess I need to start plotting a route back to my boiler for the extension system, bu&&er!

 

[Dan Robinson]

Or you could give up on the ponsy nest carp and switch to Evohome.

Will cost a few more sheckles, but...