Hi, I wonder if anyone can help with an ongoing problem I've had with my Baxi 105e combi boiler for the past 2 months?
History: Boiler is 12 yrs old & I have previously replaced several small parts, temp sensor diaphragm etc. so I have a good undertanding of my boiler.
Recent issue & work done;
CH was losing pressure (ejecting through PRV) & DHW was intermittent with temp reaching max then timing out.
Plumber replaced the rear section of the DHW Presure Differential Valve & added air into the expansion vessel.
From that moment on CH was fine and pressure remained constant but I had no DHW. When hot tap opened the pin in the Pressure Diff Valve was not moving and hence not connecting with the micro-switch. (With manual operation of the micro-switch and pulling the pin manually hot water can be achieved)
So plumber then replaced the front section of the DHW Pressure Diff Valve where the sensing pipes connect to rule out any diaphragm / bent pin issues. No Change.
I was told the sytem had a blockage as the sensing pipes going into the Pressure Diff Valve should sense the flow of water to move the pin?
I recently purchased a new Plate Heat Exchanger, as I'd read this is often the reason for overheating/blockages due to limscale build up and started the clean out job myself yesterday.
I took the whole of the lower part of the boiler apart, the pump, Inlet/Return manifold, DHW Pressure Diff Valve, Diverter Valve assembly and finally the Heat exchanger.
I cleaned everything thoroughly and due to living in a hard water area there was a lot of black flaky residue within all of those parts.
I checked that the sensing pipes were clear and the Inlet/Return manifold flow regulator was free from any gunk and after a couple of hours cleaning rebuilt the boiler.
Unfortunately there has been no change, the pin on the DHW Pressure Diff Valve still doesn't move when hot tap is opened and yes I have very good water presuure so it's not a low pressure fault.
Otherthing I have checked using the manual fault finding diagrams;
Diverter Valve Operating Head - 240v on cable and operates correctly
Only one other note that may have a bearing, the Pre-Heat part of the boiler hasn't been used for years as was really a waste of time, however when re-commissioning the boiler it was one of the tests and I realised that when the switch is turned to Pre-Heat ON nothing happens! I believe it is supposed to fire the boiler and heat water for the Expension Vessel/Pre-Heat Store even when you are not calling for hot water.
This problem has really messed with my head and three different plumbers have not been able to solve it, so any ideas would be great.
Thanks
Craig
History: Boiler is 12 yrs old & I have previously replaced several small parts, temp sensor diaphragm etc. so I have a good undertanding of my boiler.
Recent issue & work done;
CH was losing pressure (ejecting through PRV) & DHW was intermittent with temp reaching max then timing out.
Plumber replaced the rear section of the DHW Presure Differential Valve & added air into the expansion vessel.
From that moment on CH was fine and pressure remained constant but I had no DHW. When hot tap opened the pin in the Pressure Diff Valve was not moving and hence not connecting with the micro-switch. (With manual operation of the micro-switch and pulling the pin manually hot water can be achieved)
So plumber then replaced the front section of the DHW Pressure Diff Valve where the sensing pipes connect to rule out any diaphragm / bent pin issues. No Change.
I was told the sytem had a blockage as the sensing pipes going into the Pressure Diff Valve should sense the flow of water to move the pin?
I recently purchased a new Plate Heat Exchanger, as I'd read this is often the reason for overheating/blockages due to limscale build up and started the clean out job myself yesterday.
I took the whole of the lower part of the boiler apart, the pump, Inlet/Return manifold, DHW Pressure Diff Valve, Diverter Valve assembly and finally the Heat exchanger.
I cleaned everything thoroughly and due to living in a hard water area there was a lot of black flaky residue within all of those parts.
I checked that the sensing pipes were clear and the Inlet/Return manifold flow regulator was free from any gunk and after a couple of hours cleaning rebuilt the boiler.
Unfortunately there has been no change, the pin on the DHW Pressure Diff Valve still doesn't move when hot tap is opened and yes I have very good water presuure so it's not a low pressure fault.
Otherthing I have checked using the manual fault finding diagrams;
Diverter Valve Operating Head - 240v on cable and operates correctly
Only one other note that may have a bearing, the Pre-Heat part of the boiler hasn't been used for years as was really a waste of time, however when re-commissioning the boiler it was one of the tests and I realised that when the switch is turned to Pre-Heat ON nothing happens! I believe it is supposed to fire the boiler and heat water for the Expension Vessel/Pre-Heat Store even when you are not calling for hot water.
This problem has really messed with my head and three different plumbers have not been able to solve it, so any ideas would be great.
Thanks
Craig