Hi all.
Boiler - an old Baxi 105e.
Many new parts fitted in the past couple of months, including the complete diverter valve, prv, auto air-vent, hot water plate exchanger. The PCB was replaced with a 'good used' one, though i do realise how dodgy that can be in terms of fault-finding.
There are no leaks and when it is working it produces good heat around all rads, and very hot water with no faulty heating of the rads when on the 'Water Only' summer setting, a problem i had before the diverter was changed. (The old diverter was so choked with black crap that nothing moved inside it!)
Current problem : first attempt of the day at firing up the central heating, it will not fire up and though the pump keeps running the 60-degree fault light comes on, which is the 'Fault on Pump or Low Pressure'. The pressure gauge shows 1.5 bar. I then turn on the hot tap at kitchen sink three meters from the boiler for a minute, and the central heating problem disappears. Also, the CH will continue to work on demand for the rest of the day. There doesn't seem to be anything wrong with the pump in so far as it is quiet and does the job of pushing heat to all the house rads.
Where on the boiler is the sensor which causes a 'Low pressure' error to be created - is it created by a failure of the CH micro-switch to be fully activated - as for example by the activating pin in the diverter not lifting fully when that diaphragm lifts ? My only guess as to the cause of that would be a small amount of air in the diverter or nearby, given that running the hot water for only one minute or less clears the problem.
In for a penny etc... the only other gremlin at the moment, is a weird problem with pressurising the boiler through the filling-loop - don't know how to describe it quite, but it's as if the boiler is resisting the input of new water - the normal wooshing noise of water entering the system is completely absent. I've checked the water pressure at the filling loop and it is 2.5 bar after passing through a magnetic cleaner in-line. Obviously i don't need the 2.5 bar for the working pressure of the boiler but i've never seen a boiler which kind of resists the filling-loop input like this. Can't see why or how, but i thought i should include this weird feature in case in some way i can't see, this is connected to the main problem above.
Thanks for any ideas.
[ Ps: forgot to mention - a new expansion vessel was fitted last year just under the boiler on the ch return pipe, as the one buried at the back of the boiler is full of water - split rubber. It works fine, but i never checked the pressure that it came pre-charged with until just now - it was at 2 Bar, definitely on the high side as the unit has a label with 1.5 as the recommended pre-charge. I let out some of the air and hey presto my boiler pressure gauge came back to normal, dropped to 0.5 Bar, and i was able to use the filling-loop in the normal way to raise it to 1.25. So was the 2 Bar in the expansion vessel pushing against the 2.25 Bar in the filling-loop or is that too simple? ]
Boiler - an old Baxi 105e.
Many new parts fitted in the past couple of months, including the complete diverter valve, prv, auto air-vent, hot water plate exchanger. The PCB was replaced with a 'good used' one, though i do realise how dodgy that can be in terms of fault-finding.
There are no leaks and when it is working it produces good heat around all rads, and very hot water with no faulty heating of the rads when on the 'Water Only' summer setting, a problem i had before the diverter was changed. (The old diverter was so choked with black crap that nothing moved inside it!)
Current problem : first attempt of the day at firing up the central heating, it will not fire up and though the pump keeps running the 60-degree fault light comes on, which is the 'Fault on Pump or Low Pressure'. The pressure gauge shows 1.5 bar. I then turn on the hot tap at kitchen sink three meters from the boiler for a minute, and the central heating problem disappears. Also, the CH will continue to work on demand for the rest of the day. There doesn't seem to be anything wrong with the pump in so far as it is quiet and does the job of pushing heat to all the house rads.
Where on the boiler is the sensor which causes a 'Low pressure' error to be created - is it created by a failure of the CH micro-switch to be fully activated - as for example by the activating pin in the diverter not lifting fully when that diaphragm lifts ? My only guess as to the cause of that would be a small amount of air in the diverter or nearby, given that running the hot water for only one minute or less clears the problem.
In for a penny etc... the only other gremlin at the moment, is a weird problem with pressurising the boiler through the filling-loop - don't know how to describe it quite, but it's as if the boiler is resisting the input of new water - the normal wooshing noise of water entering the system is completely absent. I've checked the water pressure at the filling loop and it is 2.5 bar after passing through a magnetic cleaner in-line. Obviously i don't need the 2.5 bar for the working pressure of the boiler but i've never seen a boiler which kind of resists the filling-loop input like this. Can't see why or how, but i thought i should include this weird feature in case in some way i can't see, this is connected to the main problem above.
Thanks for any ideas.
[ Ps: forgot to mention - a new expansion vessel was fitted last year just under the boiler on the ch return pipe, as the one buried at the back of the boiler is full of water - split rubber. It works fine, but i never checked the pressure that it came pre-charged with until just now - it was at 2 Bar, definitely on the high side as the unit has a label with 1.5 as the recommended pre-charge. I let out some of the air and hey presto my boiler pressure gauge came back to normal, dropped to 0.5 Bar, and i was able to use the filling-loop in the normal way to raise it to 1.25. So was the 2 Bar in the expansion vessel pushing against the 2.25 Bar in the filling-loop or is that too simple? ]