Boiler heating house when set to Hot Water Only - Nest 3rd Gen

[StumblingTrout]

Good Evening,

Looking for some advice please...

We recently replaced the central heating system in my late grandmothers house with a Potterton Titanium 35kw Combi and Nest 3rd Gen thermostat.

New boiler is in the garage.

A few weeks ago, the heating came on full whack - despite turning the heating OFF on the thermostat - and the boiler had to be turned off to prevent occupants from cooking.

Worth noting that it was freezing outside, but unsure whether this was related. It seemed to sort itself out. I wondered whether this was some kind of frost protection somewhere in the system - the plumber reckoned it was the Nest thermostat playing up but I couldn't see how this would be the case. That issue seemed to have sorted itself out (it hasn't dropped below freezing outside since?) and all has been working fine....

However,

We have noticed that even when the physical switch on the boiler is set to 'Hot Water Only', (no heating) the radiators still get hot and seem to follow the heating schedule on the thermostat.

Should the boiler provide heating when the stat calls for it even if the switch on the boiler is set to heating off? Or can the stat override this? And what is the purpose of overriding this?

The house is currently being sold and the thermostat being replaced with a normal one for the elderly buyer, but I'm trying to establish whether there is a fault anywhere in the system (be it with the boiler that we need to get fixed before the sale completes, or the thermostat that we are removing and plan on eBaying)

The plumber who installed the boiler seems to think the Nest thermostat is faulty but he's not a Nest installer, so was hoping someone here might have some more experience with these things and be able to offer more advice.

Many thanks!

 

[Gasmk1]

is it an s plan or y plan system plumber should know

 

[Murdoch]

Installation issue(s) - get the installer back ......... or you may do better locating a local Nest installer involved ..........

 

[JVTrades]

did you not say it was a combination boiler?

 

[Gasmk1]

did you not say it was a combination boiler?

missed that bit

 

[JVTrades]

There was a similar issue with an install of mine with an rf room stat. The boiler would turn on via the room stat but not turn off. As I used all equipment from the manufacturer they sorted it under warranty. They ended up changing something in the boiler although the customer doesn't know what that was.

 

[StumblingTrout]

I had assumed that if the switch on the boiler was set to 'Hot Water Only' then that would disable the heating and no matter what the thermostat was calling for it wouldn't open the heating valve?

 

[StumblingTrout]

There was a similar issue with an install of mine with an rf room stat. The boiler would turn on via the room stat but not turn off. As I used all equipment from the manufacturer they sorted it under warranty. They ended up changing something in the boiler although the customer doesn't know what that was.

Interesting. When the boiler was on full whack and wouldn't turn off the thermostat appeared to be working fine as there is a light on the boiler that comes on when the stat is calling for heat. This was coming on and off as the temperature was adjusted so to me this said that the Nest system was working perfectly and that the issue was with the boiler, but my understanding of how thermostats interface with the boiler may be incorrect.

 

[JVTrades]

If you have the boiler turned to hot water only and the heating comes on then there will be an issue with the boiler as that shouldn't happen. How long has the boiler been installed?

 

[StumblingTrout]

If you have the boiler turned to hot water only and the heating comes on then there will be an issue with the boiler as that shouldn't happen. How long has the boiler been installed?

6 months perhaps?
So are we saying that even if the thermostat was faulty or wired up incorrectly this shouldn’t happen and points to an issue with the boiler and switching the boiler to HWO should completely prevent radiators from getting hot?

 

[JVTrades]

And how long have you noticed this issue?
But yes, if you have the boiler on hot water only then the heating should not come on except for frost protection (around 5 degrees)

 

[JVTrades]

do you have a programmer or just the room stat which you turn up and down?

 

[StumblingTrout]

And how long have you noticed this issue?
But yes, if you have the boiler on hot water only then the heating should not come on except for frost protection (around 5 degrees)

Only since the issue of the boiler coming on full heating and not turning off as we had no cause to switch to Hot Water Only before this point as the nest thermostat was controlling the heating.

 

[StumblingTrout]

do you have a programmer or just the room stat which you turn up and down?

Just the Nest Thermostat - all programming is done through the app. Thermostat in wall in lounge, speaks wirelessly to the Heat Link which is in the airing cupboard behind the lounge which is connected to the boiler. I don't think there is anything else involved, both the boiler and Nest system were installed together so presuming there was no need to add a programmer at that point.

 

[JVTrades]

I would personally run this past the manufacturer and pick their brains. I'm not familiar with nest