Chaffoteaux + Maury Britony SE80 - pressure loss

MrIzzard · 14 Dec 2005

Hi there
Thank you in advance for any help!
I've seen similar looking probs on this forum, but the trouble is most people don't follow up with a success story!

Since the cold weather started our combi boiler has been dropping pressure overnight to nearly 0 bar. All radiators have been bled and check all pipes & joints for leak - all ok.

The system will stay on happily doing the CH for days on end. But when it clicks off overnight, the pressure goes down to such an extent it won't click on the next morning.

A guy from Chaffoteaux said it could be a pin hole leak in the heat exchanger - so i isolated the CH and turn a hot tap on (suggesting that it would suck some water and pressure from the CH side), but this was not the case. Pressure still went down anyway (even with all radiators isolated and no hot taps being used). So this looks like it's definitely a boiler prob (but not heat exchanger)?

I've read alot about leaky PRV's and full expansion tanks. Is what i've described sounding familiar? Could there be any other solutions?

I'm not a plumber, but am very technical / engineering savvy. If i get the parts, can i fix myself? Don't worry - by you saying 'yes', then i screw it up, i won't sue you!

cheers in advance for any helpful words

James

HarrogateGas · 14 Dec 2005

Have you checked the blow off to see if its dripping??

MrIzzard · 14 Dec 2005

Ah yes,
Something i failed to mention.

The boiler only needs the tiniest amount of top-up to get the pressure back to about 1 (for it to kick in), but if it's filled to about 1.5 it can easily rocket to about 3 (or even into the red), and then yes, the pipe will drip a bit outside. But it only drips when the pressure is around 3 - which we try to avoid!

Does that help?

HarrogateGas · 14 Dec 2005

If the blow off has opened, my bet is that its not seated properly or there is muck on the seat. I would closely monitor the blow off pipe, my trick is to tape a sandwich bag over the blow off pipe, leave it 24 hours and if you have moisture/water in the bag....bingo your boiler saftey release valve is passing.

Also check that when heating is on your pressure isnt going too high , indicating a flat expasion vessel. it should rise no more than a bar from the 1.5 your topping it up to.

MrIzzard · 14 Dec 2005

Hi again
I've already tried the bag tied on the pipe thing, but hardly anything was it. However a couple of days ago i noticed it was dripping due to the pressure being around 3 bar (i think it was overfilled).

Could it be the inlet into the expansion vessel is faulty - so it fills up too easily when the system cools down / switches off?

weareleeds · 14 Dec 2005

Yo need to check air charge pressure @ schreader valve on expansion vessel (same as car tyre valve) should be around 1 bar.If not use foot pump to raise pressure then fill with water pressure to 1 bar when cold.Observe pressure when heating rads it shouldn't go much higher.If it does suspect blockage in pipe to exp vesselor punctured diaphragm in exp vessel.Also check glands on all rad valves (especially if they are old) as some of these may be leaking (glands are under plastic heads)

HarrogateGas · 14 Dec 2005

Ive had a few chaffs recently where the expansion vessell has been coming out the factory charged at 4 bar..........this might be worth a look. Cheap french Muck!!

ChrisR · 15 Dec 2005

See BOILER PRESSURE PROBLEMS in the reference section.
These are prone to the flexy hose to the pressure vessel blocking with sludge. This gives the behaviour of a PV full of water , when there's nowt wrong wi'it.

MrIzzard · 20 Dec 2005

Chris R is spot on!

In my original post i had moaned that when other people finally sort their problems, they don't let close the discussion! So...

After much research and head scratching, i had it down to one of three problems...

1) Perforated heat exchanger (water from CH system gets sucked through to the other side when HW tap used)

2) Leaky pressure release valve (thought it could be this as the plumber who installed our bathroom had opened this to dump the CH system. I've heard that debris can then get in the valve so it won't seal shut in the future)

3) Blocked pipe to the expansion valve. IT WAS THIS!!

I was hoping to fix the prob myself, or get it fixed in the cheapest way possible. In the end i opted for the British Gas insurance - £24 a month (higher than normal premium, due to needing the system fixed first), and after registering on Saturday, an engineer came out today (Tues) to sort it. Only took him a few mins to diagnose and unblock the pipe - so let's hope more goes wrong so i can get my £24 a month's worth!

cheers for everyone that helped
James

chrishutt · 20 Dec 2005

£24 per month = £288 per year = £2,880 over 10 years. Likely break downs in 10 years - say 5. Cost per repair = £576. Smart choice!

HarrogateGas · 20 Dec 2005

No this is Chaff..............10 years = 40 odd breakdowns!!!

plonkit · 9 Feb 2008

Thanks guys for the help with a C&M Boiler.

My son had the exact symptoms of high pressure , leaking PRV valve, etc.

A local plumber changed the expansion vessel and the PRV and the problem was still there. in spite of parting with the wrong side of £200. You know - High pressure, dripping vent pipe and no pressure before the next restart.

I removed the clip holding the pipe to the Expansion vessel and voila!! (C&M are french after all) as suggested it was well and truly blocked. A bit of careful prodding with a decent sized paper clip (be careful not to pierce the pipe!!) freed it off enough to allow the vessel to drain about 3 pints of water. I then used a piece of plastic earth sleeve , worked it into the pipe and blew into it a few times, more muck came out - I repeated this and blew some water into it as well.

After ten minutes I put the pipe back and re-charged the system - having first charged the expansion vessel to 0.7 Bar.

So far, after a couple of days it is running perfectly.

Many thanks guys.

diynot

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Chaffoteaux + Maury Britony SE80 - pressure loss

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