Two out of three radiators not heating up

[dirtyoldbrush]

Hello — if anyone's got any ideas on this one, I'd be hugely grateful!

Here are the details...

I live in a small one-bed flat (on one level). Last year I had the water tanks and immersion boiler removed and replaced with a Vaillant EcoFIT combi boiler. The fitters rerouted the pipework as necessary and gave the system a powerflush.

There are three radiators in the flat. No thermostatic valves. The smallest, in the bathroom (45cm x 45 cm) was always the hottest, while the other two rads (living room and bedroom) got warm, but not that warm. I tried balancing the system but it didn't make a difference.

The small bathroom rad needed fully bleeding pretty much every week. It's an old rad, but having to fully bleed it every week seems a bit excessive. I tested with a taper and the gas was flammable (so, hydrogen?) The other two rads never needed bleeding.

You'd think that with all this excessive bleeding, the pressure on the boiler would go down, but weirdly it continued to rise. It got to 3.2 so I released some pressure from the small bathroom rad and balanced the pressure on the boiler. Since then, the small rad has continued to work, but the other two rads don't heat up at all anymore.

A plumber from the company who fitted the system came to service the boiler (no problems there) and tried to clear what he presumed was an airlock, but it didn't work. He left mystified.

I'm guessing it's an airlock too, which this video demonstrates a method to clear it —
I can do that, but that won't address the underlying issue of what's causing the problem in the first place. If anyone's got any ideas so I can go back to the fitters with an educated theory for them to sort out, that'd be a massive help.

One other thing that might be worth noting is that the left-hand valve under the boiler was left open by the fitters (Circled in pink in attached photo). Should it be closed, like the one on the right?

Thanks in advance!

Ian

 

[ShaunCorbs]

If it’s never worked properly and they’ve fitted the 3 rads get them back to sort it

Won’t be an air lock

Also sounds like you have a problem with corrosion hence the hydrogen being generated

 

[Scott_D]

Did it ever work?

 

[Harvest Fields]

If it has never worked, did they flush the system out?

 

[dirtyoldbrush]

They removed a water tank system and fitted a Vaillant EcoFIT combi boiler and rerouted the pipework as necessary and gave the system a powerflush.

The rads were already in place, they didn't fit new ones. After the new boiler was fitted, the rads worked but the smallest, in the bathroom (45cm x 45 cm), was always the hottest, while the other two rads (living room and bedroom) got warm, but not that warm. I tried balancing the system but it didn't make a difference.

I understand corrosion causes hydrogen build up, but having to fully bleed the smallest rad every week seems a bit excessive.

Thanks

 

[Harvest Fields]

I would get them back out.

 

[Scott_D]

Try taking off the TRV heads.
Have you shut the lock shield valves while balancing?

 

[dirtyoldbrush]

The system doesn't have any thermostatic valves.

I can follow the instructions in the video that I posted to cure the current problem. What I'm asking for is if anyone has any theories on what might have caused the problem in the first place?

 

[Riley]

Corrosion as you’ve already said??

 

[dirtyoldbrush]

Seems a bit excessive to have to bleed a rad fully every week though. Is that possible? I'm not disagreeing, I'm just asking out of lack of knowledge! Cheers

 

[Harvest Fields]

Seems a bit excessive to have to bleed a rad fully every week though. Is that possible? I'm not disagreeing, I'm just asking out of lack of knowledge! Cheers

Sucking air in somewhere I would say.

 

[SGM]

I know the post is a little older. But I would advise that proven hydrodgen build up in a system is a big issue, with the volume your producing and venting the system or heat exchanger (aluminium in this case) will be literally dissolving. The system needs immediately flushed fully and correctly inhibited with only approved (by the boiler manufacturer) inhibitor. Not cheap stuff like 4trade or the likes.

3 radiators on that boiler should be roasting hot if temp is set up to a decent level on boiler stat, do you have microbore pipework on the system?