I have a Vaillant ecoTEC plus 637 system boiler, which was installed just under 3 years ago (April 2010). Of course, it's out of warranty now that the problems have started! The boiler was only serviced 3 months ago by the original installer.
Last Tuesday we woke to a cold house caused by the boiler not working. The analogue pressure gauge was at zero and F.75 was showing in the display.
I opened the filling loop and let more water in. Turned the boiler off and back on and all was okay.
On Friday morning same again. Cold house, no pressure on analogue gauge and showing F.75. Refilled and working okay. At this point I decided there must be a leak, causing the pressure to drop, although I'm not sure why this would be reflected by a F.75 error, rather than an F.22! I spent half an hour checking all the pipes around the boiler and all the radiators in the house, but found no sign of leakage. I guess it's possible that pipes under the floor boards could be leaking, but couldn't see any sign of damp patches on any ceiling, so the only place left to check would be under the downstairs floorboards, which I can't get under (due to tiles etc.).
It seems strange that this issue is happening during the night, possibly because the backstop temperature is set to 15, so the boiler stays off most of the night, allowing the system to get cold (and allows the pipes to contract?).
I turned the temperature down to 15 on Saturday during the day and left it for a few hours, in the hope of seeing a leak or a repeat of the problem, but it didn't happen and once the temperature was turned up the boiler fired up and worked as normal.
Each time I've allowed more water into the system I've noticed water coming out of the external overflow pipe, but I suspect this is because I've put too much in and it is simply allowing water to escape to reduce the pressure. Currently, the analogue pressure gauge needle is towards the top end of the grey and the digital reading is showing 2.8 bar.
As this has happened twice in a week, I've no reason to suspect it won't happen again, but currently it seems to be behaving.
Am I worrying unduly or am I experiencing the start of the dreaded F.75 problem?
Last Tuesday we woke to a cold house caused by the boiler not working. The analogue pressure gauge was at zero and F.75 was showing in the display.
I opened the filling loop and let more water in. Turned the boiler off and back on and all was okay.
On Friday morning same again. Cold house, no pressure on analogue gauge and showing F.75. Refilled and working okay. At this point I decided there must be a leak, causing the pressure to drop, although I'm not sure why this would be reflected by a F.75 error, rather than an F.22! I spent half an hour checking all the pipes around the boiler and all the radiators in the house, but found no sign of leakage. I guess it's possible that pipes under the floor boards could be leaking, but couldn't see any sign of damp patches on any ceiling, so the only place left to check would be under the downstairs floorboards, which I can't get under (due to tiles etc.).
It seems strange that this issue is happening during the night, possibly because the backstop temperature is set to 15, so the boiler stays off most of the night, allowing the system to get cold (and allows the pipes to contract?).
I turned the temperature down to 15 on Saturday during the day and left it for a few hours, in the hope of seeing a leak or a repeat of the problem, but it didn't happen and once the temperature was turned up the boiler fired up and worked as normal.
Each time I've allowed more water into the system I've noticed water coming out of the external overflow pipe, but I suspect this is because I've put too much in and it is simply allowing water to escape to reduce the pressure. Currently, the analogue pressure gauge needle is towards the top end of the grey and the digital reading is showing 2.8 bar.
As this has happened twice in a week, I've no reason to suspect it won't happen again, but currently it seems to be behaving.
Am I worrying unduly or am I experiencing the start of the dreaded F.75 problem?