Combi Boiler pressure drop - keep having to top up

[grantgibson45]

This seems to have co-incided with me bleeding a radiator upstairs around 1 week ago ?

I have got a Gloworm Combi boiler and noticed the other day that the pressure had dropped to around 0.5 bar. So I went to top it up and the person who installed the boiler fitted a blue plastic in line valve which meant that it didn't shut off initially and the pressure kept rising. So I decided to bleed the radiators downstairs whilst the heating was on to remove some of the water. This was at about 10.30 at night so I was desperately trying to shut the top up valve closed before bed. Anyway I managed to use my force to get the stupid valve shut and the system seemed stable at around 2 bar.

Then last night I again noticed the drop in pressure, so this time I topped it up shut the valve off with pliers at around 2.5 bar and went upstairs and bled the radiator in the bathroom which is a large towel rack type rad.

Since last night I have topped the system up again this morning and it remains stable for a while but subsequently drops. It is currently at about 1 bar but I don't know what is going on.

When I topped it up to 2 bar and turned the heating on to test the system this morning the pressure was going up to 3.5 bar at which point I decided to turn the central heating off.

Can anybody help with this ?

I have not touched the actual pipework on any of the rads just the bleed valves and they are all tight.

The only other thing I did the other day was turn on a small radiator the other day as we had visitors coming.

I fear it is a boiler issue ???

Cheers

Grant

 

[Burnerman]

I think you need to get the red expansion vessel checked inside your boiler, Grant.
Basically, with no pressure in the system, air is added through the valve on the top to around 10 psi or whatever the manufacturer recommends.
With this done, water is added through the filling loop until its around 1 bar.
With the heating on, the pressure should rise a little, but then fall again when the system cools.
When checking the EV valve, if water is present then its goosed....think of it as a steel bottle, the two halves of which are separated by a rubber diaphragm. On one side of the diaphragm there's the CH water, on the other side there's air, ready to be compressed as the hot system expands.
John

 

[Agile]

Before recharging press the pin and see if any water comes out. If so it needs replacement.

Repressurising is covered in the FAQ on this site.

Tony

 

[grantgibson45]

I went round the radiators yesterday and the upstairs bathroom bleed cap was ever so slightly not fully tight so I tightened it to the max and the system now appears stable at around 1 bar when cool and goes up to around 3.5 bar when running. Is this too much still ? I haven't had chance to look at the expansion vessel yet.

Cheers

Grant

 

[grantgibson45]

The boiler is a Swiftflow 100 and as such the only way to get to the expansion vessel is by removing the entire boiler from the wall. This seems completely stupid to me but I don't think there is much I can do is there ?

Grant

 

[Burnerman]

I went round the radiators yesterday and the upstairs bathroom bleed cap was ever so slightly not fully tight so I tightened it to the max and the system now appears stable at around 1 bar when cool and goes up to around 3.5 bar when running. Is this too much still ? I haven't had chance to look at the expansion vessel yet.

Cheers

Grant

Thats too much difference between hot and cold pressures......I know nowt about gas stuff, but I would hope that the EV would have been checkable in situ? Lets see what the gas lads say.
John

 

[shorky]

Sure these ev are valved at the top, have a good look at the top of the vessel, charged them on 80's before, but having the worst memory in the world i cant remember. The vessel definatly needs air in it if the pressures are going up that much.

 

[petit_pablo]

The boiler is a Swiftflow 100 and as such the only way to get to the expansion vessel is by removing the entire boiler from the wall. This seems completely stupid to me but I don't think there is much I can do is there ?

Grant

You dont have to take the swiftflow off the wall to recharge the EV. You should be able to access the shraeder valve from above

 

[grantgibson45]

The boiler is housed in a cupboard in the kitchen ... what would I have to do, take the fan flue assembly off ? The back plate of the boiler can't be removed and so whilst you might be able to access the valve on a boiler installed in a utility room I don't know if this is going to be the case on mine.

If I take out British Gas Homecare are they likely to spot the issue on first service ?

The system isn't majorly broken and the last service I had the guy just hoovered out the dust.

Cheers

Grant

 

[shorky]

Is it on the swiftflow that there is a flat bracket on the top above the vessel, held down by four self tapers, if you cant get your head over the top it might be a struggle, failing that fit a vessel external to the boiler and you will have to forget about the original one, someone else might be able to confirm about the plate at the top.