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icezebra

So, recently had the Vaillant 350f thermostat replaced with a Nest and I'm left with a problem I can't wrap my head around. Boiler is Vaillant ecoTec 831 Plus and is only a couple of years old.

With the Vaillant thermostat, the flow temperature would vary based on room temp vs set temp, but also quite regularly reach the max flow temp of 75C. Now with the Nest, which as far as I can tell is now contact closure only, the flow temperature never goes above 55C.

I can't see anything in the Nest settings about controlling flow temp, and if it's a straight switch then I can't imagine how the Nest's settings would impact it. The only thing I can think is that there's a boiler setting buried in a menu to do with this.

Tearing clumps of hair out. The house is noticeably colder as some radiators now just don't heat up as much. And rather than 30 mins to take the room with the Nest in from 19C to 21C, it now take hours; and doesn't even get there. Haven't even managed to get the room above 20C.

Help! Anyone have any thoughts? I'm not GSR so am not going to play with the innards of the boiler, but following a chat with a Vaillant installer - who had no idea, I'm trying to get an idea what this might be (and hopefully buried in settings) before I pay for someone to come round.

(Have been searching for previous questions ref this issue to no avail.)
 
does nest do weather comp?
 
It does, based upon location and internet based weather. But at times it's been bloody freezing outside, and still flow temp doesn't get about 55C. Besides, can the Nest request different flow temperature over simple on/off contact closure link? The weather comp I thought was mainly about time in advance start heating to reach target thermostat temp.
 
The nest device is a fancy thermostat. It has no control over the flow temp. Just the room temp afaik.

It has no means of talking to the boiler to read the flow temp. They can learn a few things re time -to-heat etc but not that.
 
Having said that its been a while since I fitted one and at the time opentherm wasnt properly implemented. If your boiler is opentherm and you have the new v3 nest it may be able too. You need to check your boiler compatability
 
Thanks. Nest v3 supports OT, but can't find any mention in the UK Vaillant manuals ref OT. Some searching online suggest Vaillant NL is a member of OpenTherm, but Dutch manuals aren't helpful and models seem to be different. Some suggestion online about Vaillant UK not really supporting OT and anecdotal sources about warranties / possible firmware upgrades etc.

Even then, strikes me as unnecessarily complicated though - the boiler, if undergoing c/c activation, should just try to reach target flow should it not - without any kludges with OpenTherm?
 
Yes sadly so far when something is opentherm it offers no guarantee of compatability. Its down to manufacturer implementation.

Opentherm is a set of instructions and
Methods of control.
Some manufacturers may only support parts of it.

Some boilers released early on at the dawn of opentherm time only supported very little and required add on looms to be added to offer more functionality.

Have you called Vaillant.
They use a proprietary system called Vsmart. They should tell you if they fully support opentherm
 
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Vaillants do not have open therm and nest can only alter the room temp. It has no control over the boiler.
Have you removed the complete recoiever from the front fascia? Look in the boiler settings and see what temperature it's set on.
 
Boiler temp settings are at 75C max. Key thing you said there - I believe the receiver is still there! This sounds like the problem. Boiler is expecting to be told flow temp, but only getting on/off. Brilliant. Off to check this (and get gsr person to remove of course) and will update. But I think you've resolved it!
 
Resolved! Receiver was still plugged in to front of boiler and as I didn't need to remove the case, I've just popped it out. Flow temperature rising higher already. Thanks Chalked!
 
My understanding of nest is that it monitors local outside temp and your heating patterns and combines the 2. So as a smart stat it may decide that during the warmer days it is not necessary for the boiler to be working so hard. (But I have been wrong before):p:p:p:p
 
It cant modulate the boiler if its on a vaillant which doesnt have open therm though. It can only switch it on or off. It wouldnt be able to control the modulation or the flow temperature. Not so smart after all hey.
 
It cant modulate the boiler if its on a vaillant which doesnt have open therm though. It can only switch it on or off. It wouldnt be able to control the modulation or the flow temperature. Not so smart after all hey.

Yes this is my understanding of the Nest system hence why I wondered why the OP removed a modulating system and replaced it with an on/off setup as offered by Nest.
Was it to have remote access via smartphone?
 
Hi Everyone,
I've been searching for a solution to the very same problem posted by Icezebra back in January. I have the same Vaillant 831 plus boiler and Nest setup but it wasn't clear how this issue was resolved.

The max target flow temperature is set at 75C factory default (d.71 in the menu settings) but seems to be limited to 54C when the heating is turned on controlled by the nest thermostat. The boiler manual states that the target flow temperature is set using menu setting d.5 and is noted at 54C but cannot be set higher. (The manual also states that this setting is limited by the eBUS controller if connected - perhaps this is a red herring?).

Reading through the forum Chalked asked if Icezebra had "removed the complete receiver from the front facia"?, Icezebra then said the problem had been resolved by simply unplugging the receiver from the front.
I do not understand what can be removed from the front facia in order to raise the flow temperature. The only thing that could be removed is the Vaillant analogue timer which just pops out if required.

I also thought perhaps they meant the Nest box but this cannot be simply unplugged front the front facia as it is wired into the internal wiring of the boiler. In addition, it seems odd that Icezebra would be happy to remove the Nets system without a fight :D

I would really appreciate some assistance here as it's getting pretty nippy and the flow temperature just isn't heating up the house properly! I'm sure the answer is pretty simple but any suggestions welcome! Thanks in advance.
 
Both hot water and radiator dials are turned up full. The analogue timeswitch is set to on/constant (as the nest controls the timing).
 
Yes, Nest was installed in the summer after I moved in - this is my first winter here so I can't comment on the previous flow rates. I think the 12V wire had an analogue Honeywell thermostat on previously.

I started looking into the problem once I realised the house wasn't heating up quickly and radiators just didn't feel hot enough.

I don't know but my feeling is that the previous 12V thermostat was varying the signal/resistance and informing the boiler of a flow rate where the Nest receiver is a simple on/off and does not vary the signal i.e. limiting the flow to 54C.

Does this make sense to anyone? Perhaps there is a way to set an override on the Vaillant boiler settings? Ideally Icezebra could get back in contact to confirm his solution.
 
From my (limited) understanding, your old thermostat would simply have worked as an on/off switch. I believe the Nest operates in the same way (i.e. on/off).

The OP had a Vaillant weather compensation device fitted initially and forgot to remove the old receiver so boiler flow temp was still being limited by that. I don't see that being your problem as you don't have one of those devices in your setup.

What is d.0 set to on your boiler?
 
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Thank you for your time on this.

d.0 is set to 24 which is the maximum for this boiler.
 
Hmm I can't really think of anything else to suggest. Seems like you'd already covered all the things I know.
Is yours a systerm or combi?

I don't think d.5 is an adjustable setting. I think it's a read out of the flow temp the boiler is trying to achieve: if you have a smart contoller the value is received via ebus. If you have an on/off arrangement (like yours) then my understanding is the value comes from what ever the rotary dial on the boiler is set to.
 
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It cant modulate the boiler if its on a vaillant which doesnt have open therm though. It can only switch it on or off. It wouldnt be able to control the modulation or the flow temperature. Not so smart after all hey.
Vaillant’s work on Ebus not OT so you need to use Vaillant controls to get the full benefits
 
Hi Icezebra - I have the same issue, with same Vailant thermostat being replaced by Nest V3 and 55 degree flow temps!

I cannot see the wireless receiver you're talking about - where/how exactly did you remove this?

Much appreciated :)

Cheers!
 
Remote access is available with the Internet Version of the Vsmart. Far superior to Nest.
 
Hi Icezebra - I have the same issue, with same Vailant thermostat being replaced by Nest V3 and 55 degree flow temps!

I cannot see the wireless receiver you're talking about - where/how exactly did you remove this?

Much appreciated :)

Cheers!

I think it's plugged into the front of the boiler?

Can I ask why you changed to the Nest system?
 
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