Sealed Central Heating Problem - not much heat!!

shortperson

Am afraid this might be a long description!

We have a sealed pressurised central heating system, with an unvented hot water cylinder, with a Glowworm 30sxi condensing boiler. We've always had a bit of trouble with the radiator in our lounge not getting very warm. Previously the problem has been due to a build up of sludge, which was cleared out 2 years ago and all worked fine. But last winter that rad was getting cooler again, and our bedroom rad wasn't working well either. So this year, in advance of autumn, I thought I would try and get them checked and working properly. We had a local plumber round, they drained the system, and ran cleaner through it - no difference. So they said it needed power flushing, so they came and ran some sort of flush for a couple of hours, and we ended up with a system that was far worse than when we started - now we had 5 rads not working. They didn't know what else to do, and despite saying they'd come back to me, have not been seen since - but to be fair have not asked for any payment either.

So we decided to get the system properly power flushed, at some expense. After flushing it nearly all day, I was left with a system that was working, and, hurrah, the lounge rad was lovely and hot. All was good, except a week later it went cold again, and so did the next one on the run, and now actually there's not much heat upstairs either. And the boiler is coming on for about 2 minutes, and then cycling (pump and/or fan seems to be going but no heat being created) for 3-5 mins, and then coming on again for 2 mins, and then cycling, etc, etc. So the heat is not really getting round the system now, just the first few radiators.

The powerflush people said it could be sticky TRVs, so we have changed the rads in question to just straight valves - which hasn't made any difference.

Does anyone think it's an airlock? If it is an airlock, why did it happen after a week? Or could it be a problem with the boiler? What I cannot fathom is how the system was working fine for a week, and now isn't and I hardly have any heat. I know the system can work, but what could be stopping it?

Any ideas, gratefully received!!

Canucklehead

Hi.

Do you have a microbore system?

10mm Plastic?

GSR

shortperson

It's not micro-bore, it is plastic. I think it's 15mm - certainly the pipes up to the rads (which are metal/copper) are 15mm. But otherwise it's plastic flexi pipe everywhere, thanks

Canucklehead

Hi.

Oh well.

I have been to a couple of jobs where the 10mm plastic at the manifold is a problem, obviously not in your case.

You need someone who can take the time to look at the system and work logically back to where the problem is.

Basic stuff as well like the pump and filter in the boiler (C/H return).

Was the boiler included the circuit when it was flushed? Or was it flushed from the flow and return underneath leaving the boiler out?

GSR.

shortperson

Hi there

Thanks for your reply. I've now had the people that cover our boiler out and they have replaced the pump (it had been leaking a little at one point by the look of it) and the filter in the boiler was cleaned out, but all of that looked clear of debris, and not the cause of the problem. The Magnaclean was emptied and that did have quite some debris on it (flaky black bits) considering it was powerflushed two weeks ago. So the engineer thought it could be the heating motorised valve that was stuck, so that got replaced this morning. That didn't make any difference, and now the system is staying on even less, and is making the most terrible noise, which I think is the automatic bypass valve as I had someone out to check that last week too as it was doing the same then. That time the engineer closed the bypass valve down and said it could be debris in the system but turning it down stopped the dreadful noise, which I have done again today but it's not stopping the noise. The engineer this morning said he though it could be a restriction in the pipes seeing as the new motorised valve hadn't made any difference. But I didn't want to leave the boiler on as it was so noisy and not really working anyway. And I now have the powerflush people coming back tomorrow to flush the system again...

I am at my wits end to know what else to do, but can only think it must be something in the pipes that is causing this problem as everything else that we think it could be has been replaced. I so wish I could turn back time to when just two rads didn't work very well but the rest of the system did!

Thanks

Canucklehead

Hi.

Running out of options.

I would be interested to know if the pipework is 22mm running round with tees of in 15mm for each rad or, is it 22mm to a manifold kind of arrangement.

I assume a good clear circuit through the boiler has been established?

GSR.

shortperson

Sadly we can't see much of the pipework, that we can seems to only be 15mm, so we are now thinking there's a lot of 15mm pipework and not much 22mm which probably isn't helping. There seems to be some kind of restriction in the system. The good news is the boiler did stay on last night without stopping or cycling very little, the bad news is the heat only seems to be coming through to about 5 rads properly, the rest have heat to the main pipe in, but no heat going across the rads. Seems to be no problem with flow through the boiler or to the hot water, problem seems to be on the run to the rads, flow is very low.

I too am running out of ideas and options, seemingly! Very frustrated as it was all working and now not.