Leaking heat exchanger on a new boiler

[Hugo Nebula]

Long tale of woe...

My mother's 14-month old boiler sprung a leak yesterday. The water that came out was completely black. After finding a plumber out of the Yellow Pages (Tesco Insurance's 24-hour emergency hotline, my arse!), he said the leak is coming from the cast-iron heat exchanger. He expressed surprise that the heat exchanger should spring a leak in such a short period of time, and that, if the system had been flushed properly, the water should be so black.

The boiler, an Ideal Classic FF340, was fitted as a replacement to an original system. This was supposedly power-flushed by the installers, but according to yesterday's plumber, this should have taken about 4 hours, whereas my mother reckons it was a lot less than that (mind you, she is in her eighties and does get confused, so she's not a reliable witness).

Further information that may or may not be relevant: i) All the radiators are fitted with TRVs, I think there is a by-pass, but it doesn't have any kind of flow valve on it. I fitted a room thermostat as there wasn't one before, and told my mother to keep the TRV in the same room fully open (replacing the TRV with a lockshield valve would have required a round tuit, which wasn't available at the time). My sister visited last week and turned the valve down. ii) Since the boiler was installed, it's only been used full for about three-four months. My mother went into hospital in early January, and was there for six months. While she was away, apart from a couple of weekends I stayed over, the thermostat was lowered to keep it ticking over on frost protection. Last weekend was the first time it's been used apart from hot water for 9 months.

Questions:

1. Can an unflushed system cause a cast-iron heat exchanger to leak after 14 months (unless there's a manufacturing fault)?
2. If there isn't a by-pass circuit, could all the valves being up to temperature have caused enough pressure to rupture the heat exchanger?
3. Would a long layoff or low level of usage have exacerbated this problem?
4. Who's at fault here? The boiler's manufacturer's, or the installers (name-and-shame time: Merseyside Central Heating of Crosby)?

[Set Square]

I would be surprised if a decent heat exchanger would corrode enough to leak in 14 months with as little usage as you indicate - whatever you did to it!

Black water indicates that corrosion has taken place at some time. This could have been there for a long time, and not been flushed properly when the boiler was changed - or it could have happened since the new boiler was installed if there was no inhibitor in the the system - or if *lots* of oxygen had been introduced.

I guess that it is probably a vented system - with a small fill & expansion tank in the attic - and that it wasn't converted to a sealed system when the new boiler was fitted. Is this correct? If so, is there any evidence of pumping over - in other words, when the pump is running, is there a constant flow of water out of the vent pipe back into the F&E tank? If so, this would be a good recipe for rapid corrosion!

Assuming that the boiler is correctly vented - with a clear path to the F&E tank, not interrupted by any valve - there's no way that the pump can generate enough pressure to do any damage - even when running stalled.

I wouldn't have thought that laying the system up would do any harm.

Apportionment of blame could be a bit of a challenge - because the boiler manufacturer and installer will blame each other. Start with the installer - the black water has *got* to be down to him due either to:

• insufficient flushing

• not putting inhibitor in, or

• incorrect system design

or some combination of these.

[Andrew Gabriel]

Can't find any reference to that model on the web, so I don't know what type it is.

You could just remove the TRV head, which would leave the valve fully open.

I would say not, even if the system had no inhibitor. Radiators are much thinner (unless also cast iron) and would corrode through first. My parents had an Ideal Standard cast iron boiler for around

40 years, and it never had any inhibitor in it. It only got removed because they wanted to switch to a smaller wall mounted boiler. Even allowing for thinner castings nowadays, it's not going to corrode through a modern one in 14 months IMHO.

System should either be vented or have a pressure relief valve. I don't know if it's a low water volume boiler though.

Running with the boiler stat too low can cause condensing operation in non-condensing boilers.

Sounds to me like a manufacturing fault, but would need more investigation to be sure.

[Hugo Nebula]

On Sun, 18 Sep 2005 12:04:59 +0100, a particular chimpanzee named "Set Square" randomly hit the keyboard and produced:

Yes, it still has the header tank in the loft, but I don't know if there has been any pumping over.

It seems the first and third are definitely there. Crawling round the loft space yesterday, I found an empty 1 litre bottle of Sentinel (?) inhibitor. Assuming they put the full bottle in and no more, is this enough for a seven radiator system?

I'm not hopeful of getting a response from the installer. He's got his money, and wouldn't respond to my concerns about the system last year. Short of throwing good money after bad to hire solicitors, etc to get him to put things right, what options do I have?

[john.stumbles]

Yes.

Take it up woth the manufacturers. For this you'll need the benchmark certificate (A4 white card with light blue print & logos etc on it) which the installer completed and left with the customer when he completed the job.

Didn't he!??

If he didn't then the manufacturers may wash their hands of it since the benchmark is the evidence that the boiler has been installed correctly, and you'll have to get heavy with the installer to sort it out.

[Hugo Nebula]

On Sun, 18 Sep 2005 12:15:08 GMT, a particular chimpanzee named [e-mail] randomly hit the keyboard and produced:

Did he f***!

What course of action could I take if the installer doesn't play ball or drags his feet, I wonder? Given that fact that my mother is 80, and has no form of heating or hot water except the CH, what would be a reasonable time for the company to carry out the work? Would I have to give them a couple of days, or a few weeks? If they don't, could I then employ someone else to do it and hope to claim the money back off them?

How long does it take to order a replacement heat exchanger? Is it a next day delivery type of thing, or would it be, "ooh, we may have one in our Stornoway depot, it might be here in a couple of weeks". And how long to fit?

[Set Square]

That should be enough - unless, of course, it has somehow got diluted. This can easily happen if the water level is too high in the F&E tank. When the system heats up, the water expands and runs out of the overflow. When it cools down, the level drops - and fresh water comes in through the ball valve. Or there could be an undetected leak somewhere - maybe under the downstairs floorboards? - again with automatic topping up with fresh oxygenated uninhibited(!) water.

Have you examined the boiler yourself to verify the plumber's diagnosis? Is there any chance that there's just a leaking joint rather than a corroded heat exchanger? The heat exchanger is probably in several bits which bolt together - with gaskets to seal the joints. Unless there were a serious manufacturing defect, it seems more likely to me that a gasket has failed than that the metal has corroded through.

[fred]

Before talking to the manufacturer I'd be inclined to power flush the system properly (including the boiler) and refill with inhibitor, sounds like the power flush will be needed on the final system anyway and it gives the manufacturer one less thing to find fault with if they carry out an inspection.

Note that I'm not suggesting a deception, as others have suggested, I think it unlikely that the system caused the leak so it seems fair to clean up a little to avoid a rejection of any claim.

It sounds like you're putting it down to experience but if you decide to pursue the original installer for the cost of re-flushing (at least) then you could probably do with a report from the plumber you called out first.

Just noticed your latest post, don't worry about lead times, just call in the mfr, mention aged mum to express the urgency and it is their problem - but I would clean up the system first.

[Hugo Nebula]

On Sun, 18 Sep 2005 13:53:08 GMT, a particular chimpanzee named fred randomly hit the keyboard and produced:

Unfortunately, any water in would just cascade over the kitchen floor.

I certainly don't want to chalk it up to experience, but in the first instance, she needs a working central heating system, and if she's to have to pay out to a third party for someone to provide that, then our only hope is to try and recover that from someone. I don't want to take actions now that's going to stymie that ("you didn't give us a chance to examine the system even though we couldn't get someone out there until mid-November").

[Aidan]

Assuming they put the full bottle in and no more, is this

Yes. There's a moulding date on the bottom of the Sentinel bottle, which might give you an idea of it's vintage. I dosed my system yesterday, the bottle was moulded 11 months ago but had been in the garage for 4 or 5 months awaiting tuits. And they should have completed the self-adhesive label on the bottle.

You've got to ask him, though. Maybe a letter with a copy to the manufacturers. A copy to the local press if he blanks you. I'd be mortified if something I'd done failed witin that time. I also believe that you'd still have a claim, in that it should have lasted much longer, even though the 12-month guarantee may have expired; that's one for UK-legal.

Questions:

I'd think I could get it to fail that quickly, but I'd have to try really, really hard. The problem could be 1) dissolved oxygen due to a) pumping over (as mentioned) and/or b) galvanic corrosion. I'd guess pumping over. It might also be 2) fireside corrosion due to low return temperatures (assume it's not a condenser since it's CI). Given the evidence of corrosion, I'd think we're talking about 1a or

1b.

You could plug the hole with that epoxy putty stuff, refill and set the system running, WITHOUT firing the boiler, to see if you can get it to pump over under any conditions. If so, I'd reckon it's negligent installation. The 'by-pass TRV' shut condition would probably be the worst case for this. In fact, all TRVs shut, but pump still on, might be the worst possible case, depending on where the cold feed and open vent connections are, see below.

You could also get a sample of the water in the system (unless it's all been diluted or drained). Low pH (less than 7, acidic) would be the worst case for galvanic corrosion. This could be caused by great gobs of active flux, inadequate pre-commissioning flushing and/or no inhibitors. Ideally it should be around 8 or 9 (alkaline). I'll see what pH my system is, out of interest, if I can find some litmus paper. If you know anyone in secondary school, the chemistry lab technician would test a sample of it for them & marvel at their sudden interest in applied chemistry.

No. The pump's maximum differential pressure (at no flow) is tiny. You'd need great pressure which you can't get with an open system. You could get huge pressure, easily, on a sealed system, with no expansion vessel & no pressure relief valve.

If there's black sludge (magnetite) it's likely corrosion. However, with all TRVs shut, the flow rate would decrease and the pump differential pressure would increase. This might start pumping over, although there may be none under normal flow conditions.

Could be a manufacturing defect but the installer would be my prime suspect. A new boiler might be simplest to get Mum's heating on again asap. I'm not sure you could get these boilers still (non-condensing presumably).

[fred]

In article , Hugo Nebula writes

I see, but you could isolate the pipework to flush through. There is a risk that sludge might have moved through the system and dumped in the heat exchanger, if the mfr sees something like that then it would be a big negative.

Yes, good to get it sorted now, re. evidence, got a video camera?

[John]

Cast iron heat exchanger, tough as old boots. One of my old reliable modesl which could be expected to last forever.

Yes but I would suggest very unlikely. How long did its (presumably cast iron also) predecessor last?

Its not.

The 340 is a modern version and IIRC its got a limited range stat response so it shouldn't be possible to run at that low a setting even at number 1 on the scale.

Ideal will be most interested. Contact their customer service department in Hull. I have had "one" similar failure on a 370 which I installed for a client. Ideal sent me a replacement heat exchanger and refractory panels since the old ones were slush. I sent them back the old holed unit which had blown a hole in the back of the casting after three years. They examined it and cancelled the invoice for the replacement. They also paid me £145 plus VAT to cover my labour as well. I had already hosed it down and taken photos of the failure which I felt were caused by a blow hole in the casting which had been sealed with casting mould material until it gave way after a long time in case of debate but my apprehensions were unnecccessary. You should discuss this with your installer but if they won't play ball phone Ideal anyway

John

[John]

SNIP

No its a one piece casting job with pipes straight into the ports, metal to metal

[Hugo Nebula]

On Sun, 18 Sep 2005 11:15:00 +0100, a particular chimpanzee named Hugo Nebula randomly hit the keyboard and produced:

I had another look at the heat exchanger today; there looks to be surface rust on its underside, whether this is from the leak yesterday and today I'm not sure, but it looks too much for 24 hours. Would this have a bearing? [I'll try and post a few photos, but my ISP isn't cooperating.]

What I thought was a discarded bottle of inhibitor was a boiler de-scaler, probably from a previous attempt to cure the previous noisy boiler. In answer to a question, the old boiler had been there for at least twenty-five years.

[Hugo Nebula]

On Sun, 18 Sep 2005 22:59:45 +0100, a particular chimpanzee named Hugo Nebula randomly hit the keyboard and produced:

See

for photos of the heat exchanger.

[John]

I would guess there is a blow hole in the casting somewhere between the finning. Only way to be sure is to take it out, cut it in two and examine it. Have you got a flexible optic inspection tool? Ideals will more than likely assist - see my other post on this matter.

John