Vaillant boiler not heating radiators. Please help!

[Rystar00]

Thanks guys. I really appreciate your help as the house renovation has been so stressful and this is topping it off! Especially considering

Yes I have a magna clean but none of these particles are being trapped. The water samples are all clear - it's just when I took the bleed valve off that I noticed all of these debris particles coming out!

Do you think it's worth asking the radiator company to pay for the power flush?

 

[ShaunCorbs]

Thanks guys. I really appreciate your help as the house renovation has been so stressful and this is topping it off! Especially considering

Yes I have a magna clean but none of these particles are being trapped. The water samples are all clear - it's just when I took the bleed valve off that I noticed all of these debris particles coming out!

Do you think it's worth asking the radiator company to pay for the power flush?

You could ask but bet you there's something in the small print saying must flush the rads out first

 

[Rystar00]

Just checked the instructions and it says I must flush the heating system out first not the radiators (the plumber did this when commissioning the boiler). I will write to them and see what they say.

What I'm concerned about is each of these radiators having some debris in them and when the boiler was fired up it circulated the debris and it's all collected somewhere which is causing the poor circulation. Don't know what il do if I have to rip floors and carpets up!

So weird that the water is clear when draining and in the magna clean but there is a load of carp near the bleed valve that seeped out when I added the chemicals!

 

[Riley]

Sometimes carp does collect at the threads. I think there's more to th than meets the eye. Do any of the radiators warm up properly

 

[Rystar00]

Yes some of them warm up more than others. If I turn off all valves apart from one rad then that one gets roasting.

Just read up on 'sludge Flakes' and I'm worried that my picture shows them. Apparently they're difficult to remove with a power flush. Getting really worries now as the system was piped in uponor so unlikely that there was any flux etc left in there and that all these flakes have come from the radiators and have collected somewhere and we won't be able to remove them.

 

[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

 

[Rystar00]

Sorry Riley!

I have the vsmart which comprises of a VR65 wiring centre and a separate room stat (comes in the same box)

 

[Riley]

I'm reckoning wiring fault did Vaillant guy check wiring

 

[Stoney Ground]

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.

By doing what I said in post 45, 3 weeks ago you would have proved this.

 

[Riley]

I'd get Vaillant back mate you've proven the system works

 

[Rystar00]

Thanks Riley - I will get them back. They said to change the range rating on the boiler downwards but that's had no effect. I understand from searching other forums that I'm not the first to have had this problem.

Stoned Ground - fantastic advice thank you. I showed your post to my installer (he probably hates me now!) and he followed those instructions to identify the issue.

I will keep you posted on what happens next.

 

[Stoney Ground]

Sometimes it's easier to take away external controls to prove they are or aren't the problem. Maybe ask Vaillant to send a senior technician they need to prove to you there is not a fault with their system.

Have they tried a full factory reset of boiler and controls?

 

[Rystar00]

I thought it might help if I took the boiler from 'auto' under the heating load to the actual load.

I have calculated my rad heat output as 18,137kw so how much should I allow for my unvented cylinder please? 2kw? Would it then be a good idea to set the heating load at 22kw?

Thanks again guys!

 

[Riley]

Right you've proven that your radiators get hot yes ?
You did this by essentially taking the zone valve out of the equation?
I think you are looking at a control or a wiring issue
I'm not sure that there is a kilowatt loadage issue

 

[Rystar00]

Hi Riley,

Thanks again for your support. Your advice has been incredibly helpful and generous.

Yes we have established that the rads get hot (by manually opening the zone valve when the boiler 'thought' it was heating hot water) so the installer agrees and thinks it's a wiring/control issue.

I thought adjusting the load might help as I wonder if the boiler is going into anti-cycling mode too quickly if its oversized? It's probably something as simple as the wiring or controls but I've read other forums that have posts with similar problems to mine and that's what they suggested.

 

[Riley]

Have you got Vaillant coming back I think you are just clutching at straws a bit at the moment mate you need to go at this with a plan rather than just randomly changing stuff in the hope that it will fix it. My suspicion would be that there is an issue with the wiring centre