Potterton Performa 28 losing pressure - I am losing the will

Brigadier · 17 Jan 2010

Hello all,

I seem that, whatever good fortune I ever have in my life, it will always be offset by CH "issues"

I had a DHW "issue" about 10 days ago, which ended in scalding hot tap water pee-ing out of the kitchen tap for about 45mins.

Since then (although may not be related), my boiler is losing pressure at the rate of about 1 bar per day, perhaps more.

I cannot see any leaks (although haven't had every floor up - yet), and I am as certain as I can be that there is nothing coming out of the pressure relief pipe outside.

I had to have the expansion vessel re-pressurised a few months ago, as it was as flat as a pancake and the boiler was gaining pressure quite alarmingly.

I need some ideas - could it be a simple fault with the expansion vessel? (and if so, where is the water going?) Is it more likely to be a leak I haven't found yet? Could it even be a perforated heat exchanger? (in which case, is there a test for such?)

Failing all of the above, could anyone recommend a trustworthy engineer in the Cannock area who could (guarantee?) to fix my troubles, and possibly prolong my life by a year or two?

Brigadier · 17 Jan 2010

Oh, and have some rads that need bleeding, but can't (due to rounded-off bleed nipples

- previous occupants, I presume)

Burnerman · 17 Jan 2010

The fact that your system is losing pressure means that there is a leak somewhere, unfortunately. The common places are the PRV, the automatic air vent on the boiler or the stems from the rad valves.
If these all definitely prove perfect, then the heat exchanger may be the only cause.
If the expansion vessel is full of water (tested at the air fill valve) then the diaphragm withion is shot. The boiler will then dispose of excess pressure through the PRV.
I would seek help here, before you go digging up floors etc...if the boiler is at pressure and the central heating pipes are isolated, an internal leak has to be suspected.
Bad luck about the rad bleeds too...there has been a few posts about this lately...I fill up a brass bleed key with Araldite, press it over the bleed nipple, let it set and try to undo that way, if all else fails.
John

Brigadier · 18 Jan 2010

Thanks for the advice, John

I am as near as certain as I can be that there is nothing coming out of the pipe outside (even stuck my little finger in to check for dampness - stop it!) - nothing on the three or four occasions that I check yesterday.

Somebody somewhere has never once looked at their CH, and never had a problem in 20yrs......and then there's me

Brigadier · 1 Feb 2010

Progress (of sorts).....

A heating engineer friend of mine told me to turn the heating off while leak-hunting (so that any glands shrink and leak, rather than swell and seal). Makes sense - not knowing any better, I thought leak-hunting would be best done with the heating on, so that the pressure would be up a bit.

And bingo! Two very-slightly weeping rad valves, which I've nipped up.

He popped around on Sat evening, and plonked a load of leak sealer into the porch rad. He checked the boiler and could see no evidence of a leak there.

He also told me that, if I hadn't had any work done for a while, the pipework itself springing a slow leak was fairly unlikely. So, we'll give the sealer a week or so to pootle around, and the water to boil off and stabilise a bit, and we'll see where we are at then. Fingers crossed.....

MANDATE · 1 Feb 2010

If and when hot water comes out of the PRV, the pipe could well be dry by the time you test it. Best to secure plastic bag on end of pipe and see what you catch.
You say expansion vessel was re pressurised, but was it done correctly.
Just increasing the pressure to the requirement of 10psi does give any guarantee that the exp vessel contains only air. It is essential the surplus water has a escape route when its pushed back by the diaphragm.
If the diaphragm cannot move back, you are left with too small a air pocket to compress and still nowhere for the extra water to go when heating is used, except through the PRV

Brigadier · 2 Feb 2010

Thanks Mandate

Of course I can never be sure about anything, so I have to take it on trust. Will tape the plastic bag up.

But wouldn't the vent pipe (in the house) get warm if water was passing, or would the quantity involved be so low as to not warm the pipe?

Agile · 2 Feb 2010

Brigadier said:
Hello all,

Failing all of the above, could anyone recommend a trustworthy engineer in the Cannock area who could (guarantee?) to fix my troubles, and possibly prolong my life by a year or two?

You have later mentioned a "heating engineer" friend !

Is he not the ideal person to help you sort out anything? Or is he not trustworthy?

Or perhaps he follows my advice of not working for friends?

Tony

MANDATE · 2 Feb 2010

Brigadier";p="1497856 said:
Thanks Mandate

Of course I can never be sure about anything, so I have to take it on trust. Will tape the plastic bag up.

But wouldn't the vent pipe (in the house) get warm if water was passing, or would the quantity involved be so low as to not warm the pipe?

I make a hole near the top of the plastic bag, so if it fills it acts as a overflow.
The PRV opens at 3bar and will close again as soon as pressure is released, so the amount of water lost will be quite small.
If there is insufficient 'air' capacity in the expansion vessel to cope with the water expansion then the pressure will go up beyond the 3 bar, PRV opens and closes, you adjust the pressure and the whole process repeats itself.
The vent pipe will get warm just while the hot water passes for those few seconds.

Baxmax · 2 Feb 2010

Is your boiler the H.E ?

Brigadier · 3 Feb 2010

Hello all,

Baxman - I don't "get" your last post. Better spell it out for the thicko me

I trust my H.E. friend, but don't like bothering him too much - I pay him each time, but don't want him to feel compelled to turn up, give "mate's rates", etc.

Will "bag" the vent pipe and go from there.....

Brigadier · 3 Feb 2010

Oh, and the pressure doesn't seem to go up much - I doubt it could get all the way to 3 bar

Baxmax · 3 Feb 2010

H.E =High Efficiency

Is it a Potterton Performa H.E ?

If it is you might have a leak in the secondary heat exchanger.

steve32 · 3 Feb 2010

if it is the H E leak sealer will block the sec heat exchanger
self cleaning flux left in system will pin hole the sec heat exchanger

Brigadier · 7 Feb 2010

Right,

It's a Potterton Performa 28 (I can see not mention of H.E.).

I have bagged the vent pipe outside, and can see no evidence of any water passing through that in 24hrs, during which time I've lost 0.5 bar of pressure.

Will do the rad. valve checks again

diynot

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Potterton Performa 28 losing pressure - I am losing the will

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