Gas heating system problem

e_m20

I am hoping someone can help. I have a Grant 45f gas boiler in a sealed system. Last week I found that the aav was leaking so I drained out enough water to bring the pressure down to zero and replaced the valve. I then repressurised the system to 1.2 bar and it worked but every couple of days the pressure goes back up to 3 bar and leaks out of the prv so I have to remove several litres of water to drop the pressure back to 1.2 bar. Cananyone suggest a solution? I don't see any fitting on the expansion vessel to check or adjust the pressure.
Thanks in advance.

JohnnieK

e_m20 wrote: »

I am hoping someone can help. I have a Grant 45f gas boiler in a sealed system. Last week I found that the aav was leaking so I drained out enough water to bring the pressure down to zero and replaced the valve. I then repressurised the system to 1.2 bar and it worked but every couple of days the pressure goes back up to 3 bar and leaks out of the prv so I have to remove several litres of water to drop the pressure back to 1.2 bar. Cananyone suggest a solution? I don't see any fitting on the expansion vessel to check or adjust the pressure.
Thanks in advance.

The fact that it happens every few days would suggest that the top up valve could be passing and gradually increasing the pressure (if it's mains fed that is) If the expansion vessel was bust it would happen more or less straight away ( a couple of hours after boiler start) and that the pressure dose not revert back when the boiler is off.

aujopimur

Once filled you should disconnect the filling device.

e_m20

aujopimur wrote: »

Once filled you should disconnect the filling device.

Thanks guys. I will replace the top up valve and hopefully that will cure it.

e_m20

Happy to say that I changed the top up valve and the problem is solved. Thanks to all for the help.