HELP!!!! Biasi Combi M90 24S No Pressure

Lizbet30

I have been in my house for a year. During that time I have had no problems with the boiler which is a combi for my hotwater and CH. I joined Homeserve as they give you a free service once a year and yesterday a Corgi engineer came out to service it giving it a clean bill of health.

The next day my pressure was at 0 and I could not use CH or hot water. My CH has been off since May and the only reason I knew it was not working is because I tried it before I saw the pressure was at 0. When I saw the pressure was down to 0 I added more water from the filler loop, taking it back up to 1.5. I then tried CH and hot water and both were working again and were stable. However, when I turned off the CH, the pressure dropped again to O. I again filled the boiler to 1.5 and tried the hot water. It is stable while it is running but after switch off over the course of about 10-20 mins it drops to O. I phoned up Homeserve and they sent out another engineer from the same company and he refilled the boiler and ran the hot water and again the pressure valve was stable. The hot water was turned off and he waited for a while but had to go to another job. After 10-20 mins the pressure then dropped again to 0. I phoned them back and they are now saying that I must have a leak but there were no problems yesterday!! I have looked over the whole house and can find no leak(unless under floorboards or in walls) and it must be a massive leak to take 20mins to empty boiler!!!

After he had gone I refilled the boiler and ran the CH for 2 hours with no drop in pressure at all. Even when running the hot water at the same time there was no drop. However, as soon as it was turned off the pressure went to 0 again within 20 mins.

Please help. Basically I need to know could the service engineer have caused this by knocking something in the boiler? He gave it a full service but did not touch anything else.

I have looked on DIY sites and the options are:

1 A leak - I have checked and cant find one.
2 Pressure relief Valve - have checked this and no water coming out.
3 Expansion vessel - don't know anything about this but could this be possible?
4 Air in system venting through automatic air vent - could this be possible?
5 Diverter or diaphram?

Are any of these possible. I have checked the first two. Would really appreciate any advice at all. Thanks.

barrymung

Repost as tyhe first one failed...

Assuming you can find no leaks eslewhere in your system...

These boilers have a "safety pressure release" valve. This could be faulty and releasing water/pressure. It vents water into a small pipe that comes out under the boiler and could be connected to a nearby drain pipe or may lead outside or under the floor so you may not be aware it's happening. Check if you are losing water via this pipe!

The pressure vessel could indeed be faulty. A good plumber can check this (Indeed you can check it yourself with a pressure guage)

Generally you'll hear excess air being vented by the internal purge valve. I suppose this valve *could* be faulty and not venting air but think it's not likely.

Alternatively, the pressure guage on the front of your boiler could be kerfuggered and giving a false reading!!

Lizbet30

Hello. I have checked the Pressure Relief Valve as it goes out the side of my house and no water is coming from there at all. I know this works because 7 months ago when I was learning how the system worked (no manual left by previous owner) I put too much water in through the filler and the pressure went past 3 so water was leaking out at the side of my house. I then bled the radiators until pressure went down and all has been fine since.

I wondered too if the pressure guage was faulty but when it gets to 0 then the central heating and hot water only come on for a few moments then cut out which must be a safety mechanism. If there really was pressure there and it was just the guage faulty would this still happen? It could be just a coincidence that the service guy was out yesterday but is there anything he could have knocked/not put back in place that would be causing this?

whatatwit

Somewhere I have a leak in my CH system, when we have the heating on at night, it's fine. Turn off heating and next time it won't work. I have to fill using the loop and it's fine.
Over the summer (ha ha) I haven't had the CH on and the hot water has worked fine.
The leak may only be tiny, the water will be being forced out under pressure and I don't think the system takes that much in when using the loop.

You might have more joy in posting on the DIY board.

Lizbet30

whatatwit wrote: »

Somewhere I have a leak in my CH system, when we have the heating on at night, it's fine. Turn off heating and next time it won't work. I have to fill using the loop and it's fine.
Over the summer (ha ha) I haven't had the CH on and the hot water has worked fine.
The leak may only be tiny, the water will be being forced out under pressure and I don't think the system takes that much in when using the loop.

You might have more joy in posting on the DIY board.

Hi. My issue is that my hot water worked fine all through the summer until the boiler was serviced yesterday. My CH worked fine all year until May when I switched it off. My CH is on a timer and if I just leave it and fill up using the loop at night the pressure will be at 0 by the morning and so the heating will not come on at all. I just wondered if there were any other possibilities rather than a leak. If it is a leak how can I find it if I cannot see any damp patches at all and my Pressure relief Valve to outside is not dripping water? Which DIY board do you mean I should post?

whatatwit

Hi, it's the DIY board on here.....a bit further down the home work and play section.

Lizbet30

Thanks for getting back to me. They are going to come back today so will see what happens. If it is a leak it must be massive as I filled up to 1.5 from empty 7 times yesterday and there is no evidence of water anywhere. The pipes go under the floor and are on the ceiling of the cellar and I can see no dripping and the walls show no discolouration. An odd thing happened this morning when I again filled up the boiler to 1.5 and turned on the heating. This time it went up to 3 and the PRV did start venting outside. I needed to bleed nearly 4 litres out from a radiator before it became stable at 1.5. It then stayed there. When I tuned off the heating it stayed at 1.5 for an hour. When I turned on the heating again though. It went down to 0 again. Am going to suggest The diaphragm i Expansion vessel is perforated to them. The thing is if I had a leak I would have known about it. I have never had to top up the filling valve before except when I first moved in. It does suggest the service caused this. Any more ideas from anyone?

Canucklehead

Hi

As your boiler is on the first floor it would be safe to assume that it is not the boiler leaking otherwise you would have noticed quite a few litres of water appearing somewhere around it.
You are looking for a leak under the floor ,maybe you could try and find a loose floorboard(in a cupboard?) and see if you can see,hear a leak or smell damp.(torch and a mirror are useful)
I would be checking your expansion vessel as it might have lost it's pressure which might explain the big pressure rise and subsequent dumping out of the PRV.
I would not be blaming the service guy at this stage.

Note. As you have refilled the system repeatedly you should have some inhibitor added when the problem has been resolved .

Corgi Guy.
Have you noticed any other expansion vessels elsewhere on the system?( Large red football size steel tanks)

Lizbet30

No have not noticed any other expansion vessels. I know you say I should not blame the engineer but there were no issues with CH or hot water until they came. I never had to use filling loop and all ticked along fine. The very next morning no pressure at all and no hot water or CH!!! I just want to sort this out. I really cannot have a leak as I refilled boiler with filler loop 7 times yesterday. That amount of water would be detected surely? Will say about the inhibitor. Still waiting on the engineer from Homeserve.

Lizbet30

The Homeserve engineer has just left and thoroughly checked the boiler. I explained about having to top the boiler up 7 times yesterday and he isolated the boiler and found it was secure. Therefore he says it can only be a leak but yesterday at least 10 litres of water must have come out as I kept topping it up when boiler pressure went to zero so the leak must be massive.

It seems probable that because we had no issues before the service man came on Tuesday and the CH has been off since May, when the original he came out to check the boiler and pressure it must have either started a leak or popped a join in the pipes. The issue is now where this massive amount of water is since Tuesday as there are no visible signs. Our house is an old Victorian terrace and the boiler is in a bedroom on the first floor. The pipes go down into the floor and into a boxed unit in the lounge below next to the fireplace and into the cellar, being open in the ceiling (we have not done up the cellar so easy to see in the joists. There are no leaking pipes in the cellar and no pools of water. I have checked all the ground floor ceilings and all the walls and radiator joins. He thinks that the solution may be the kitchen extension put on the house at a later date so the cellar does not run under there. This means that they are under a concrete floor which is covered with slate tiles. He thinks that a joint may have popped under the floor on Tuesday. Does this sound right?

They are going to now get a plumber out to check this and he says they should isolate the pipes going to the kitchen first and check the pressure in the system which will let them know if that is definitely the issue. What I don't understand is that there are no signs at all in the kitchen floor (or ceiling) of water seeping upwards through the floor. Would the water just go into the ground then? The boiler has been topped up at least 10 times since Tuesday and so we are talking a lot of water. Would appreciate any comments. There were no issues with the CH from July 2007 when we moved in until May when turned off and we have had hot water all summer with no issues until Tuesday. The only time I have ever had to top up the pressure was when I first moved in a year ago as I noticed it was at .5 and then no issues until after engineer came on Tuesday. Thanks.

Canucklehead

He thinks that the solution may be the kitchen extension put on the house at a later date so the cellar does not run under there. This means that they are under a concrete floor which is covered with slate tiles. He thinks that a joint may have popped under the floor on Tuesday. Does this sound right?

Almost certainly the problem area. Unless there's anywhere else that you can't see pipes.

Corgi Guy.