I have an old Baxi boiler with a separate hote water cylinder installed in 1992. I presently have a situation where the expansion tank is over-flowing when the system is on & coming out from the overflow pipe.The system loses pressure so I have to adjust it (with a screw driver turning a valve to let in air-between Bar 1 & 2)Otherwise it loses pressure & needle falls to zero.
Last week I had a situation where Br Gas were called in with their one off charge to fix a problem which they said was due to a faulty alternator valve ie when the thermostat indicated the hot water was warm enough the central heating switched off- he said he replaced the valve)
Does anyone have an idea as to where the fault lies in the system?
Right, from what i can make out you have a sealed ch system on a standard cylinder (not unvented). I think the coil in the cylinder has a hole in it. Thats where your ch pressure is going. Its going into the cylinder up into your tank and making it overflow. So you need a new cylinder.