Nest thermostat compatibility

proformance

Hi guys,
We have a pretty old Vaillant gas boiler and wired thermostat situation.
The Google Nest site says we are compatible, but I wanted to know if anyone has experienced any challenges, particularly with older boilers?
Thanks!
Z

Ibrahim5

I don't see why there should be a problem with older boilers. You need to look at the heatlink(it comes with the nest) and your boiler and control valves. Do you understand how the control system works? If you understand how it works there should be no problem. Your old thermostat is just a switch. The heatlink is just 2 switches (one or heating and one for hot water). If you understand how it works it will be easy. If you don't understand how it works you won't be able to do it. You can't just guess. It's hard to tell from your question how experienced you are.

fenwick458

I can't think of any boiler that wouldn't be compatible with it.
ok maybe one of these wouldn't be compatible!
but apart from that, if your boiler runs off gas and electricity then it'll be fine

Jeepers_Creepers

The Nest is an amazing piece of kit. It will 'learn' the best settings to provide you with what you need.

For instance, I guess you currently turn on your heating at a certain time in order for it to be warm for when you get up? Sometimes that will work fine - your house will be at the right temp at 7am, other times it won't have reached what you want, other times it'll have got there waaaay before - what a waste, man

The Nest will teach itself when it has to come on to give you the temp you want at the time you want - it'll vary from day to day depending on overnight room temp.

And other cool stuff like that too.

The recent models are also 'Opentherm' compatible, which means they have a much finer control over 'Opentherm' boilers (which yours certainly ain't...)

BUT, after the Nest has done all its amazing wizardry stuff, all it essentially then does is tell your boiler 'come on, now'. And, 'that's fine - go offski.'

So, yes, it'll work.

fezster

proformance said:

Hi guys,
We have a pretty old Vaillant gas boiler and wired thermostat situation.
The Google Nest site says we are compatible, but I wanted to know if anyone has experienced any challenges, particularly with older boilers?
Thanks!
Z

Yes it will work. It's just a switch (as others have said above). You can also use your existing thermostat wiring to supply 12V power to the nest wall mount to keep it in the same location. I'd advise you get a professional to fit it, if you are unsure.

proformance

Thank you guys, that's good to know! I wasn't sure if certain boilers were able to modulate the heat up and down properly and instead just chuck out loads of heat or off completely.. Imaginer a very spikey graph... thus rendering the Nest's steady modulation promise rather useless.

I didn't know Nest used Opentherm... But isn't that irrelevant if my boiler doesn't 

fezster

Nest brands it's TPI as True Radiant, I believe. It needs to learn how quickly your house heats up, but it should prevent the temperature overshoots.

Obviously, open therm would be better, but as you said, you need a compatible boiler for that. 

Jeepers_Creepers

proformance said:

Thank you guys, that's good to know! I wasn't sure if certain boilers were able to modulate the heat up and down properly and instead just chuck out loads of heat or off completely.. Imaginer a very spikey graph... thus rendering the Nest's steady modulation promise rather useless.

I didn't know Nest used Opentherm... But isn't that irrelevant if my boiler doesn't 

Almost all (prob all) modern boilers 'modulate' themselves. In other words, as the rooms heat up and the rads don't lose so much heat and the return water temp is therefore getting higher, the boiler will turn itself down to try and just maintain the right amount of flow to keep things tickety-boo. Eg, a 30kW boiler will commonly reduce its output down to as low as around 7kW in order to just keep this ticking over nicely. If that's still too much, it'll shut right off.

Opentherm - as I understand it - is another level of control where the room stat itself tells the boiler what to do - what output to give. As the desired room temp is approached, the room stat will tell the boiler to ease off, pal. The boiler does what it's told, and the lower the output, the more efficient the boiler runs. I think the idea is that if you can keep the boiler chugging out just what's actually needed, then that's better than any 'on and offs'.

That's it in crude terms.

When you have a non-OT boiler, the Nest won't be doing this. Ditto with a non-modulating boiler - the Nest won't be any more sophisticated in controlling the boiler than a standard room stat would - ie 'on' and 'off'.

How old is your Vaillant? My GlowWorm is 16ish years old, and is a modulating type, so you can hear it wind down when the rooms are getting warm and the return temp is increasing. When the room reaches the set temp, it shuts down completely. My stat is a Heatmiser, so it's just 'come on at 6am at 20oC, and down to 18oC at 9am...' etc, and the boiler follows this. On cooold morns, it therefore won't always get the rooms up to temp for when I hoped, so the only way for me to compensate (if I could be bovvered) would be to set the Heatmiser to come on more early. Your Nest, however, should be constantly learning what's going on, and adjust itself to give you the room temp you want at the time you want it - if it needs to come on more early, it'll do so. In mild weather, it might leave coming on until just a half-hour before. It 'learns' the time that's needed to warm your house. So that's one major way a Nest is better than my Prog Stat - a Heatmiser.

When you then fit an OT boiler, it'll be ready for this too.

proformance

Jeepers_Creepers said:

proformance said:

Thank you guys, that's good to know! I wasn't sure if certain boilers were able to modulate the heat up and down properly and instead just chuck out loads of heat or off completely.. Imaginer a very spikey graph... thus rendering the Nest's steady modulation promise rather useless.

I didn't know Nest used Opentherm... But isn't that irrelevant if my boiler doesn't 

Almost all (prob all) modern boilers 'modulate' themselves. In other words, as the rooms heat up and the rads don't lose so much heat and the return water temp is therefore getting higher, the boiler will turn itself down to try and just maintain the right amount of flow to keep things tickety-boo. Eg, a 30kW boiler will commonly reduce its output down to as low as around 7kW in order to just keep this ticking over nicely. If that's still too much, it'll shut right off.

Opentherm - as I understand it - is another level of control where the room stat itself tells the boiler what to do - what output to give. As the desired room temp is approached, the room stat will tell the boiler to ease off, pal. The boiler does what it's told, and the lower the output, the more efficient the boiler runs. I think the idea is that if you can keep the boiler chugging out just what's actually needed, then that's better than any 'on and offs'.

That's it in crude terms.

When you have a non-OT boiler, the Nest won't be doing this. Ditto with a non-modulating boiler - the Nest won't be any more sophisticated in controlling the boiler than a standard room stat would - ie 'on' and 'off'.

How old is your Vaillant? My GlowWorm is 16ish years old, and is a modulating type, so you can hear it wind down when the rooms are getting warm and the return temp is increasing. When the room reaches the set temp, it shuts down completely. My stat is a Heatmiser, so it's just 'come on at 6am at 20oC, and down to 18oC at 9am...' etc, and the boiler follows this. On cooold morns, it therefore won't always get the rooms up to temp for when I hoped, so the only way for me to compensate (if I could be bovvered) would be to set the Heatmiser to come on more early. Your Nest, however, should be constantly learning what's going on, and adjust itself to give you the room temp you want at the time you want it - if it needs to come on more early, it'll do so. In mild weather, it might leave coming on until just a half-hour before. It 'learns' the time that's needed to warm your house. So that's one major way a Nest is better than my Prog Stat - a Heatmiser.

When you then fit an OT boiler, it'll be ready for this too.

Hiya - great reply and pretty much aligns with what I thought.
I have a Vaillant Turbomax - not sure it;'s exact age - maybe 15-20 years old if I had to guess? It works fine mind..