This one is driving me mad.
Water was dripping outside through the discharge pipe, so checked the boiler pressure guage and it was indicating 3.5 bar! Initially suspected the Pressure Reducing Valve. It was looking wet also. Pulled the cartridge out and it was in a bad shape internally. Fitted a new one after cleaning out the valve casing. Repressurised the system checking the external expansion vessel had 3.5 bar of air pressure inside, as stipulated. Pressure rose again to 3.5 bar inside the boiler without turning on the boiler (i.e. water still cold) !! Grrr
Next thing, is the small gate valve damaged through the filling loop as this was still connected? On disconnecting it, noticed that non-return valve was leaking slightly and some water exiting the boiler, but no sign of water passing the gate valve into the boiler. Changed the NRV anyway and fitted a new filling loop and gate valve as I had one.
Repressurised the boiler to 1.5 bar, shut the filling loop valve, disconnected the filling loop and pressure again rises slowly to 3.5 bar!! Grrr
Checked the boiler safety valve and this is functioning correctly. Quarter turn and it dumps water and pressure through the discharge pipe. Leave it to opperate normally and at 3 bar, it opens slightly releasing pressure to a drip, drip, drip outside through the discharge pipe.
So how can the system be repressurising with the filling loop disconnected? The mains pressure is higher than 3.5 bar if it can somehow enter the system, but how can it enter with the filling loop disconected?
Any advice appreciated.
Chris
Edit. The boiler is a Vaillant Thermocompact VU GB 282-5
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Water was dripping outside through the discharge pipe, so checked the boiler pressure guage and it was indicating 3.5 bar! Initially suspected the Pressure Reducing Valve. It was looking wet also. Pulled the cartridge out and it was in a bad shape internally. Fitted a new one after cleaning out the valve casing. Repressurised the system checking the external expansion vessel had 3.5 bar of air pressure inside, as stipulated. Pressure rose again to 3.5 bar inside the boiler without turning on the boiler (i.e. water still cold) !! Grrr
Next thing, is the small gate valve damaged through the filling loop as this was still connected? On disconnecting it, noticed that non-return valve was leaking slightly and some water exiting the boiler, but no sign of water passing the gate valve into the boiler. Changed the NRV anyway and fitted a new filling loop and gate valve as I had one.
Repressurised the boiler to 1.5 bar, shut the filling loop valve, disconnected the filling loop and pressure again rises slowly to 3.5 bar!! Grrr
Checked the boiler safety valve and this is functioning correctly. Quarter turn and it dumps water and pressure through the discharge pipe. Leave it to opperate normally and at 3 bar, it opens slightly releasing pressure to a drip, drip, drip outside through the discharge pipe.
So how can the system be repressurising with the filling loop disconnected? The mains pressure is higher than 3.5 bar if it can somehow enter the system, but how can it enter with the filling loop disconected?
Any advice appreciated.
Chris
Edit. The boiler is a Vaillant Thermocompact VU GB 282-5

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