Combi boiler depressurising?

Had a call from a tenant of mine last weekend to say that their heating was out; I went round and found it was caused by the combi boiler having become depressurised. I quickly refilled it, and showed them how to do it, but with a strict direction to call me if it happened again.

Bugger me, they've just let me know it's happened again, so clearly there's a problem which needs sorting out. I'm going round again tomorrow to have a closer look.

My good news/bad news is that I have a service contract on the boiler but not on the radiators; ie if it's a leak somewhere in the CH pipework then I'll fix it myself; but otherwise the engineers will do it. I'll check for leaks tomorrow, but think it's the less likely cause - the system has been running fine for years and hasn't been disturbed, and unless it's in pipework under a floor I'd think a leak of this size would have been fairly clear. I'm hoping expansion vessel? Boiler (Sime "Friendly Format") is probably about 15 years old and it hasn't gone before.

What I'm asking now is for any tips I can look for tomorrow (in the absence of any obvious leaks), really to nail down whether it's the boiler or hidden pipework at fault, so that I can phone the engineers on Monday knowing what I'm talking about!

Reply to
Lobster
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If there's a problem with the expansion vessel - which seems likely - the following will happen:

  • You will refill the system cold, and set it to (say) 1 bar
  • When it heats up, the pressure will rise to over 3 bar (it shouldn't normally go above 2 bar), the pressure relief valve will open and water will drip out of the emergency release pipe - which goes out through a wall to the outside world.

So if you (a) watch the pressure gauge and (b) locate the outside pipe and watch for water coming out of it, you'll gather some evidence.

If you do find high pressure plus water dripping outside, it means that there's a problem with the expansion vessel. If this happens, the vessel may be shot - in which case it needs replacing - or it may simply have lost its charge pressure - and pumping more air into it may fix it.

Let us know what you find, and come back for more help if appropriate.

Reply to
Roger Mills

Unlikely that the CH plumbing has suddenly developed a leak, so I'd say the odds must be on a boiler fault. But, if you're losing that much water in a week, there should be evidence somewhere. Maybe the pressure gauge is buggered (the sensor gets gummed up I think).

Reply to
stuart noble

Odd. I went round, all was working fine, and there doesn't appear to have been any fall in pressure since they last topped up the system, which was on Thursday (which apparently was when it shut itself down); having previously refilled last Sunday.

Couldn't find any evidence of any leakage; hard to tell anything sensible about the PRV since it was a very wet day.

I decided to give it one more go - if and when it shuts down again, I'm fairly sure it must be boiler-related, and I'll get the plumber straight round.

Thanks for the advice guys

David

Reply to
Lobster

Then tape a plasic bag over the PRV outlet:-)

Reply to
ARW

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