Another central heating thread

[Taurus]

Rather than jump on Vegas' thread - I'll start a new one. Bit of a saga.....

My folk's central heating & hot water is off. Last week the boiler was firing up then cutting out. It's an old system with a newish boiler (Vaillant 428). The boiler temperature was rising very quickly when it fired, then it shut off. There are no boiler fault codes, but it was showing a code relating to water flow. (S.53 - Appliance is within waiting period of the operation block function due to water shortage. VL-RL spread too big)

The pump was running and was hot, but the pipes downstream varied between hot and cold.

They had the controls for heating and hot water set to max, and the boiler was simply shut down. I turned the controls to about 60% and the boiler would cycle on and off. But the radiators never got above warm.

I thought it was a water flow problem so checked the header tank in the loft (fine) and cleaned the magnetic filter (totally blocked). No difference.

At that point I had to travel home so they got a guy in who fitted a new pump and all was well - for a day. Now it's back to the same condition. They called the guy back who has spent 3 hours on it and it's no better.

I am an hour away so can't get there for a couple of day due to work - so just checking a theory.

I've tried to get them to take out a BG service contract - but not getting far on that score

My hunch is that it is still a water flow issue. I could hear 'jingling' in the larger pipes running to the boiler and the magnetic filter was absolutely solid with debris. I think the original pump was either blocked or it's impeller had failed. It was certainly running. My theory is that the new pump's impeller is now also blocked with debris.

I'd drive over and remove the pump - but work makes it impossible until later in the week. So in the meantime thought I'd ask on here and see if anyone has any bright ideas?

[Tim]

We really need an @lee function

[Lee]

Taurus, do you have the GC no. for the boiler? If it's on an open vented system, there's a small chance the cold feed from the header tank may be blocked, which would stop the tank filling the system as and when it loses any water content. Are there any untoward noises coming from the pump?
There may also be a filter on the boiler somewhere which is blocked and causing the issue. If the magnetic filter is pulling out an awful lot of muck, then the best thing, and only real solution is to have the system powerflushed. The one thing with BG is that they don't cover water quality so being on contract with a muck issue still wouldn't help, however they offer a lifetime guarantee with their flushes so long as you are on contract.

[Taurus]

The header tank feed is clear, that was my first thought which took me through a mountain of fibreglass insulation. I haven't heard the new pump running, but the old one sounded OK. It's just that the only thing the other guy did was to replace the pump and that got it running again, perfectly, if only for a day.

I don't have the GC no. for the boiler here, I'll look when I can get over. And I'll check the installation paperwork for any signs of a filter. Given that I suspect the problem is much related that would certainly be worth checking. The magnetic filter was absolutely full.

[Lee]

Did you open up a drain off downstairs and see that the header tank started to fill up?

[Taurus]

No - I didn't drain anything off. I can try that when I next go over there. When the pump kicked in there was a small flow of water back out of the intake for a second.

[zuluman]

Just a few thoughts:

has this suddenly occured that the rads are lukewarm or has it been getting worse over the last no of years?

Is it a two storey or single storey?

If a vent on a rad is opened on an upstairs rad furthest from the boiler (or if single storey furthest from boiler) does water spray out or trickle or nothing come out?

Is it clear, black or red in colour?



When you say a samll flow of water back out of the intake do you mean water came out of the vent pipe over the feed and expansion tank?

Is the 'jingling' air in the pipe?

[Taurus]

I suspect it's muck in the system that's blocked the impellor on the original pump - if the vanes were full of crap then the pump is pretty useless. And I'm guessing the same has happened to the new pump. I know when they had a new boiler fitted the guy struggled to get flow through the system, and it's been flushed twice over the past few years.

The flow when the pump kicked in was out of the water inlet pipe. Unfortunately the guy they got in came when I couldn't be there so I couldn't check the old pump. I'm working silly hours at the moment, but I might get there Thursday evening.

[Lee]

If it's still blocked or full of muck after being flushed twice in the last few years then it's not been flushed properly, and there may be an underlying issue like it pumping over in the loft causing it to drag air back in, which in turn accelerates corrosion.

[zuluman]

IF it is sludge that is the problem AND it the system has been flushed a number of times, it is disturbing to note that the sludge is reoccurring.

If it is debris, then where is it from? Would want to be a lot of copper filings or maybe hemp etc to block it.

have you checked if there is a non return valve stuck somewhere?

IF it is sludge then it was not flushed properly or there is a design fault or a constant leak on the system.

IF it is sludge (which in reality is ferrous oxide -rust- formed in the presence of very little oxygen), it will be black. If the oxide is formed in the presence of excess oxygen, it wil be red - thus my request what if anything is flowing at a rad vent?

Unchecked, this sludge will rot the radiators (esp pressed ones of light material) causing pinholes and leaks.

It is not without danger to powerfush such a system. To thoroughly clean it, you use a 'cleaner', which can be aggressive and if the rads or worse still underground pipework (might be gunbarrel in some houses) are near rotted, it may complete the process.

Electroyltic corrosion can also occur between copper (pipework) and steel (rads)

A powerflushing machine is used. To really flush you could turn off all the rads and leave one at a time open - flush it each way. Repeat for the rest of the rads

Then you put in a protector to keep the system clean - basically forms a plastic film over the internal metal parts to stop the water corroding. e.g. fernox

Anyway, try and ascertain what exactly the problem is first. I am a bit suspect that sludge would block the new pump so quickly. It tends to fall to the bottom.

You know you have a sludge problem when the system is 'working' as the rads will be cold in a half moon shape from the bottom

[Taurus]

I know the magnetic filter was full, but apart from checking the header tank I haven't had time to drain off any water from the system so I've no idea what colour it is. What came out of the filter was pretty black. I'll report back once I've had time to get over there and check it a bit further. Last time I'd just called in so I didn't have any tools on me.

[Taurus]

Well I got a phone call from the folks who'd found an engineer, who I spoke to. The filter is clogged solid again and the pump is as well. So I've asked him to sort out a full flush. The guy who did it 2 years ago obviously didn't clear it very well. We'll see what that does.....

[zuluman]

More worrying is IF the last guy did do a good job - why is the system clogging up at all and so fast?

The engineer might need to inspect the design and point out if there is a problem causing this - otherwise you could be looking at the problem again in another few years

As it is the rads/pipework may be corroded. Let us see what he finds

[Taurus]

They moved in there when I was 12 - and had the central heating installed then. So it's been there for cough 9 years now.

I spoke to the guy as there's no way I can get over there before next week now. He's going to give it a thorough flush, with the warning it may reveal pin holes in a few radiators. Sounds like a decent chap so hopefully he'll sort it. I did say to them a while back they needed to think about replacing the system, but it's like everything, people don't want to spend money on something that's working.

[zuluman]

[QUOTE=Taurus;80808]They moved in there when I was 12 - and had the central heating installed then. So it's been there for cough 9 years now.

So you are only 21? ...

or 21 and a 'bit'?

9 years is young for a heating system - but I think its older ...