Wondering if someone could help with a problem we are having with our baxi 105 he combi. The pressure keeps dropping even after repressurising with the filling loop even when the boiler is running cold. Drops about 0.5bar per hr at the moment but seems to have got worse since I bleeded all the radiators. A friend of mine thought it could be the expansion vessel as cannot find or trace any visible leaks on the rads, boiler or pipework. Anyone any ideas?
Combi boiler problems
- Thread starter Memphis
- Start date
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There should be a pipe going to outside from your boiler, this is called a PRV, Pressure relief valve, find a small balloon or small bag, freezer bag etc and either tie this over the end of the pipe or use an elastic band to secure it and if water accumulates in whatever you use then you do indeed have an expansion problem, it is well covered in the Wiki on here
Ok, left it over night at 1.5 bar with heating off and found pressure gauge dropped to 1bar. Checked the PVR and found nearly a cup full of water in the bag I had tied on.
I put the heating on this morning and pressure increased to 3.5 bar and had to release some through bleeding a rad. Looks like this is the expansion vessel? Only thing I can't understand is why this would all suddenly get worse when I bleeded all the rads. Would repressurising the boiler damage this?
I put the heating on this morning and pressure increased to 3.5 bar and had to release some through bleeding a rad. Looks like this is the expansion vessel? Only thing I can't understand is why this would all suddenly get worse when I bleeded all the rads. Would repressurising the boiler damage this?
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It gets worse because water is less compressive than air!
Once you bleed all the rads there is no air left in the system to absorb the pressure rise created by heating expansion.
Your pressure vessel usually has this pocket of air present to accommodate that expansion.
It either needs recharging via the schrader valve or has failed and needs replacing, probably along with the PRV which often fail after they have been activated.
Call a local recommended RGI and have the boiler serviced at the same time. Set aside approx £200.
Once you bleed all the rads there is no air left in the system to absorb the pressure rise created by heating expansion.
Your pressure vessel usually has this pocket of air present to accommodate that expansion.
It either needs recharging via the schrader valve or has failed and needs replacing, probably along with the PRV which often fail after they have been activated.
Call a local recommended RGI and have the boiler serviced at the same time. Set aside approx £200.
It would mean removing the cover from a room-sealed gas appliance which can compromise the seals if they are in a poor condition. This is something many non-RGIs fail to realise when the take the cover off of their boiler!
MI states that if ev needs changing, the boiler needs to be removed from the wall... Ouch!
That's going to be a bit of a PITA!
If it just needs recharging one might be able to contort oneself and a pump onto the valve... Can't tell without being there!
If it's knackered then would be better to fit a new additional vessel on the return somewhere more accessible!
If it just needs recharging one might be able to contort oneself and a pump onto the valve... Can't tell without being there!
If it's knackered then would be better to fit a new additional vessel on the return somewhere more accessible!
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