Nest heating issues

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Morning all,

I've had a Nest fitted for a few months now and so far everything has been brilliant. However, since Sunday I've been having some strange issues that I can't figure out.

So to start I've got a Worcester Bosch 24i Junior combi boiler, and my Nest heats up the radiators as per usual but it sits at around 16c and not matter how high I set the thermostat it won't increase the temperature.

There doesn't seem to be a disconnect between the Heat Link and the Thermostat, and I restarted it yesterday just to see if that'd work. The HeatLink connects to the boiler properly as when I reset the HeatLink yesterday the boiler didn't respond to any changes on the thermostat.

I'm at work at the moment and as a test I've turned my heating on from my phone to 22c, it was at 11.5c when I did turned it on around an hour ago. It doesn't seem to have moved in the time since.

Does anybody have any idea of what is going on?

Here's an example of what'll show on my phone app

https://i.imgur.com/K998ViH.jpg

 

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Increasing the thermostat temperature will not increase the air temperature any higher if the radiators are unable to heat the air up that much.

So you say the temp sits at around 16 now. What was the temp reaching before? Are the radiators getting as hot as they were before? Has the location of the thermostat changed? Has the environment in which the thermostat lives changed?

I've turned the thermostat off (via the Android app) and it's still hovering at 13c, which doesn't make sense as it's freezing outside so should be a lot colder.

Last night the Nest turned on but it was sitting at 16c and not getting any hotter, the screenshot above is an example of what would show yesterday. It'd say heating but wouldn't actually get any hotter.

The radiators aren't getting as hot unfortunately, I've bled them to ensure they aren't the issue and it's still the same issue.

On Friday the radiators were blazing hot as I wanted, it was set to 22c and they were definitely very hot.
No change in regards to the location or environment (apart from it's much colder now)

 

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Lots to check when home.

I'm leaving work early today to spend the afternoon playing around with it.

* Is the boiler on?
Yep, it definitely turns on and if I turn the heat link off then the boiler will stop heating the house (it still turns on for hot water)

* Is the pump running? (might be built into the boiler)
I think so, I can hear the boiler doing it's thing so assuming it is

* If you have a hot water tank too, does the valve that chooses where the water go work, does it change position if you set the Nest to hot water? if not, might be jammed/need replacing.
No hot water tank, just a standard combi boiler

* Do the radiators have TRVs (on the inlet/outlet, dial from 1-5 or similar, let you set the per radiator temperature)? Turn to max
Yep, TRVs everywhere. They were all set to what I wanted them to be and have worked perfectly fine till a few days ago. (living room 5, bedroom 2 etc)

* Are all the radiators getting warm? If not, then the TRV might be stuck.. Most are easy to pop off, under you will find a pin, push it in/out manually a dozen times or so to ensure its free then put TRV back on and set to max)

Yep all radiators getting warm, just not to the temperature I want them to be. The Nest seems to stick to one temperature

* Are the radiators warm top to bottom (once heating has run for a while).. might well need to bleed them
I've bled them all again yesterday just to double check

* Is the house getting warmer?
It is, but again the Nest for some reason wont change it's temperature no matter what mode I put it in

* Is there an old thermostat in the house somewhere (ours is still wired in, job for next year to remove it... If I dialled it down to 15oC then I would get similar symptoms as it would turn the heating off once the house hit 15oC)
Nah that's been disconnected

* Are there are warnings/messages on the boilers display, might be a low pressure cutout kicking in. Wont apply to older systems.

No display on my boiler, but pressure was fine when I looked yesterday.

 

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2. The house is not getting warmer and the number isn't changing. This would imply the Nest is correctly reading the ambient temperature but there is a fault with your heating system preventing it from warming up your house enough to increase the temperature above 16 degrees.

From the sounds of it, 2 seems more likely.

This seems likely but I'm not sure if it's a Nest issue or boiler.

I got home almost two hours ago and turned my Nest onto 22c, my Nest is currently sitting on 13c
The boiler is definitely heating up and the radiators are as well, but they definitely aren't 22c hot. I have a control knob on the front of my boiler, I've put that onto Max to see if that makes any difference so lets see

 

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Nest does control the boiler temp if its wired up for opentherm hence why i asked above, but a quick search suggests the boiler isnt compatible anyway, so as above its boiler related

Sorry mate, missed that post. No, it's not opentherm

Can you touch them and hold your hand there?

I can for a bit yeah, definitely not piping hot like I'm used to but still fairly hot.

It'll be the heating system, all the nest does is turn your boiler on until such time as it measures the temperature is the same as what you set the target as.

If it's measuring 13 after 2 hours of heating and the house doesn't feel warmer, then the heating is not making your house warmer, nothing Nest can do about this.

If my heating was on for 2 hours straight I'd be sweating buckets even if outdoors was in minus figures.

So this evening I set it to 22c as per usual and the radiators definitely got hot but no way near 22c.
At around 8pm I turned it onto eco mode, the boiler then shut off as you would expect. But the Nest was still showing 16c and still is showing 16c despite the fact that it's set to eco mode.

Spoiler: IMAGE

On the weekend I'll clean my filter out and see what impact that has made.

 

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As already alluded to in this thread, I think its most likely to be something to do with your boiler.

But I'm not sure you understand how a thermostat works. What do you mean by the radiators were no way near 22c? Do you mean that you don't think the radiators are as warm as 22c? If you set your thermostat to 22c do you expect your radiators to reach that temperature?

What should happen when you set your Nest to 22c is that the boiler kicks in to heat up the radiators. These, in turn, will heat up the air to 22c. At this point, the boiler turns off. During this process, your radiators will likely reach more like 60c.

Looks like you're setting your thermostat to 22c, the boiler comes on, the rads heat up, but they're not doing enough to bring the temperature of the air around your thermostat to 22c. Its reaching 16c ish. I know the air around mine is only reaching 17c at the moment. My rads aren't powerful enough to get this any higher.

Before, when everything was okay, was the air temperature by the thermostat reaching 22c and then turning the boiler off??

Sorry for not replying, been proper busy last few days.
I should have been clearer, my radiators aren't getting hot enough and the ambient air isn't getting to 22c. I had the heating on for about 12 hours on Saturday and not once did my Nest get to 21c The highest it reached was around 18c (which luckily was OK).

I'm going to drain my system out this week and pour some X400 inhibitor in there to see if that has any impact.

 

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Radiators should be so hot that you're unable to hold your hand on them for more than a second or two. Also it can be freezing outside but 13 inside. My house will cool to 12 over a day from 20 degrees. It will sit at 12 for a long time in these freezing temps.

My house losses a lot of heat (it's a single brick building), compared to last year I'm losing a lot less heat than previously.
That's why I was surprised it wasn't as cold as I'd expect it to be

 

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So yesterday I cleaned my Fernox filter for the first time and there was a load of gunk on there.
I'll clean it again around NYE just to see if it's collecting loads.

I'll be pouring the X400 inhibitor in there this weekend.

Just to make sure I'm doing it right do I:

1. Drain the system
2. Open the heated towel rail and pour a litre in
3. Close heated towel rail and then refill the system
4. Do I then turn the heat up and leave the system running?
5. After 2-3 weeks drain the entire system again and refill.

I'm a bit confused what to do after putting the inhibitor in the system, any help would be appreciated