worcester bosch combi 230 rsf boiler presure 3 bar plus

[ih]

my 82 year old mothers boiler is giving her problem whereby when heating is demanded the pressure jumps to over 3 bar and dumps water outside.
1. late last summer no heat so diverter valve was replaced- all ok
2. early november the pressure started dropping identified leak at the ch flow and return both little piglets were changed- all ok
3. Now when heat is demanded the pressure jumps to over 3 bar
i intend to check the expansion vessel please advise is there anything else i need to check to solve this problem for her.
Thanking all in advance for advise and help .
ih

 

[ddk]

there could be a few things causing this problem. first, ensure the filling loop (assuming you dont have an integral one) is not passing water from the cold mains into the heating system. secondly, the domestic hot water heat exchanger (looks like a bottle mounted horizontally in the boiler) could be corroded inside and mains pressure water could be leaking into the heating system. thirdly, and most probably the cause if the pressure only rises when the heating is on would be the expansion vessel. This can be checked by removing the schraeder cap (like the valve cap on a car tyre) from the expansion vessel, and pressing the spindle to see if there is pressurised air in, or if there is water in it. If the expansion vessel has water coming from the valve then a cheap/temporary fix would be to 1/2 drain a radiator, preferable one in a spare room, or some where where the heat isnt as important. the air in the top of the radiator should be enough to allow for the expansion of the water when the temperature rises.

 

[h4gg13]

you have a problem with your expansion vessel.
If you decide to replace the vessel it would be advisable to replace the pressure relief valve at the same time as it may not hold pressure which tends to happen when they have been opened.

 

[gas4you]

See FAQ's on checking the EV. If water comes out of the EV valve it is knackered

 

[ih]

you have a problem with your expansion vessel.
If you decide to replace the vessel it would be advisable to replace the pressure relief valve at the same time as it may not hold pressure which tends to happen when they have been opened.

sorry forgot to mention prv was replaced when the flow and return were replaced

 

[ddk]

even though youve had a new pressure relief valve it is still advisable to replace it whenever it has been passing, or at least remove it and give the valve seat a good clean and a wipe with silicone grease to ensure there is no dirt/grit on the valve seat which will cause it to pass water

 

[ih]

hi
thanks to those who advised. The EV is knackered!! On pressing the valve very little air with water came out so according to FAQ i need to replace EV tank. Can i replace or is this corgi job? If i can then will appreciate any guidance on replacing it so i am prepared and this will make the job easier.Also does the pressure need to be Zero?
thanking in advance.
ih

 

[gas4you]

You can DIY this if you feel confident. No gas related parts are involved.