Opentherm System Boilers for Nest v3

[andyman22]

We're currently in the midst of a complete refit of our house, extending into loft and ending up with three bathrooms. As we used to have a vailant combi which struggled when more than one tap was run, we've decided to go for a system boiler.

And once I started researching thermostats, system boilers etc, I stumbled upon Opentherm.

My current thinking is to get a Opentherm compatible System Boiler, but I wondered if these were a thing, or is Opentherm only really for Combi boilers? Intergas advised that Opentherm works on their Combi boilers, but would require some kind of relay setup (by me or the plumber) to work on a unvented System.

I've tried speaking to the plumber that our builder uses, but he only seems to know about Vailant and WB, and has experience of the Evohome. None of which I was thinking of using.

Realise I'm probably coming across as very naive here, but wondered if any of this made sense, and whether its reasonable so look for a System boiler that is opentherm compatible?

Thanks.

 

[vulcancontinental]

Actually Nest3 isn't Open Therm though they're probably working on it. Apparently they've been a bit prematurenwith their announcements. There are several OT boilers and some that are not can be converted but not easily and not, I think, the Worcester.

 

[Dan Robinson]

Nest ahve fooked up big style.

They might be able to salvage it with software updates though depending on what the true cock up was.

Fitted one this afternoon for a customer and certainly wasn't impressed with it.


Opentherm just fires the boiler at 100% rather than the required %age.

Apparently it works with Intergas boilers as it is supposed to, but I haven't seen it first hand.

 

[shambolic]

Logic system and heat only boilers have open therm controllers if you use the outside stat too.
But Nest doesn't give open therm control.

 

[Dan Robinson]

I've tried speaking to the plumber that our builder uses,

You might as well wipe your arris on a bit of paper and talk to that. Unless of course he is an independent installer that the builder gets in. Thier in house plumber is not going to nerd out (as I described it to a customer today) and research anything other than the cheapest solution for his governor.

 

[andyman22]

Thanks for all the replies. I saw on Nest's site that the Opentherm implementation seems not 'fully' implemented, but reading some other sites it appears it's coming in a future firmware update (or here's hoping) in the next couple of months.

So am I right in thinking that an Opentherm compatible controller (such as a fully working Nest v3...) would be able to control a system boiler in a modular fashion, without the use of external relays?

Also, any reason why Opentherm isn't very popular with boiler manufacturers over here, whereas it seems the opposite is true in Germany and the Netherlands?

 

[muggles]

It's a common problem - there's a lot of really good tech in mainland Europe that isn't marketed over here. OpenTherm has been around for years, but uptake in the UK market has been utterly rubbish. A properly working OT system would modulate the boiler flow temperature to give the most balanced and efficient system. Nest will hopefully catch up but there's no guarantee. Do you want WiFi access, or just OpenTherm?

 

[andyman22]

Just opentherm I believe. The wifi access for external temperature etc is handled by Nest, so I believe all is need is the opentherm control.

Seems very odd how we're behind on the heating side of things, especially with our climate!

 

[muggles]

Sorry, I think you've misunderstood my question. Let's try again...

Are you personally interested in having a thermostat that can be controlled remotely, or do you just want an OpenTherm compatible thermostat? IE, how important to you is remote access?

 

[andyman22]

With you now. Remote access is handy as we have family who use our place when we go away, so being able to turn the heating off when they're gone is useful. I'm guessing if remote were not needed, there's more opentherm thermostats that fit the bill?

 

[muggles]

Indeed...without remote access, you get a bit more choice! Currently, the only two OpenTherm-compatible(ish) remote access stats I can think of are Nest 3, and EvoHome. It's a shame Honeywell's Single Zone stat doesn't work with OpenTherm (at least, I don't think it does - @Dan Robinson @simond can you comment on this?) as that would solve the problem!

 

[Dan Robinson]

It very much does work with OpenTherm, as well as remote control.

It will even put boiler fault codes onto the display.

Which is now than Nest will.

I certainly don't rate Nest that highly. But she what I'm going to do with the 2 we have left in stock.

 

[vulcancontinental]

The single zone stat works fine with the OT bridge if set up correctly. Nest 3 doesn't. Tado says it does but I can't confirm, others are on the way. The different protocols used by Vaillant, Worcester and Viessmann mean adaptors have to be used on their boilers for OT if not using their brand controls. In fact I'm not sure Worcester have one available at all.

 

[andyman22]

Thanks for everyones help. Am I right in thinking that even if an Opentherm System Boiler is purchased, it'll need an (own brand?) adaptor to be fitted onto the boiler, or will it be compatible with an opentherm thermostat right out the box?

 

[Dan Robinson]

It depends.