Vaillant boiler not heating radiators. Please help!

[Riley]

The positive being that if each rad will get hot when it's on on its own then you have circulation.

 

[Rystar00]

Thanks Riley.

One radiator in particular only gets lukewarm when I isolate it. 90% of the others get hot. Is that a bad sign?

Unfortunately that's the one with pipes under our tiled floor!

 

[Riley]

There's nothing to say that the pipes for that rad can't be isolated at either end

 

[Rystar00]

Hi guys,

Me again!

Just thought I'd keep this post updated in case anyone reads this thread and has similar problems.

Had the installer in today and we've ruled out blockages in the pipe work and the radiators being piped wrongly.

If you remember - the boiler heats the hot water really well (burner on max and flow temp at 70 degrees) but when the demand for hot water was satisfied it started hearing the rads but flow temperature would start at 70 degrees and then lower until it hovered around 45 degrees. This happened even though we disconnected the Internet (so no weather compensator data used), the room stat in the fridge (3 degrees) and 'comfort override' mode on.

We then tricked the boiler when it was heating hot water to heat the rads instead (at 70 degrees with burner on max) by manually opening the motorised zone valve. All of the radiators (bar a couple that had dodgy valves which we've now fixed) and all the rads were roasting. So the pipe work and rads are fine.

So the installer thinks it might be the controls. However Vaillant have come out twice and not identified the problem. I think it might be the fact that the boiler is oversized (30kw but have 14 rads over 4 floors plus unvented cylinder) so it might be in anti-cycling mode? What do you think?

 

[ShaunCorbs]

I still think it's something to do with weather comp it's the only thing other than somthing drastic as its prity much all standard kit wired to s plan

 

[Rystar00]

Thanks Shaun.

Why do you think that is please?

As far as I'm aware the weather comp data is collected from the Internet so with that switched off it has to rely on the room stat which was sat in the fridge?

Tempted to get a bloody basic on / off switch instead!!

 

[Riley]

I do agree with Shaun re the symptoms. I just can't see how with a v smart as there's no external sensors

 

[Riley]

Switch might be a good place to start

 

[ShaunCorbs]

The reason I say is if it was one of the controls not much on the heating side port valve and room stat it would be doing it for both heating and hot water

The only way other than to remove anything regarding weather comp is wait for the cold weather and see if it heats up then

Unless you could trick the weather comp to think you living in the North Pole if you have to set it manually where you live ??

 

[Riley]

Hang on hang on hang on just re-read your first post do you have a room thermostat in addition to the one that comes with the V-smart