Hi All, Hope you're well. Quick recap of my shop boiler woes. (18 year old non-condensor)
2 years ago it broke so I took out the 6 months "guarantee fix" insurance for £300. After about 10 visits and half a dozen different engineers who changed primary and DHW Heat exchangers, diverter valve, pump head, insulation etc it was back working but making a hell of a noise but back to working again.So this year We've had the random F.22 (dry fire) error sometimes continually, sometimes the boiler would run for most of the day so we're back on the process of elimination. Replaced NTC sensors which temporarily appear to fix things but they were e-bay cheapies so I replaced them again with proper Valliant ones which still didn't make a difference.
First thing I noticed was significant pressure swing so ordered up a new pressure vessel, filling loop valve (which has been leaking for years), Pressure relief valve, new Flu kit, FLow/Return service valves.
oh and a vortex 300 filter.
Expansion vessel was shot, flue also mutilated by original install or by "engineer" levering it off to remove primary HEX. The other symptoms have been the boiler working but then going into burner anti-cycle so the water gets hot and then the burner shuts off and the pump pumps water around for 10 or 20 minutes even though the system temp has dropped to 30 degrees or so.
So having put on the new expansion vessel, and valves etc it was running virtually silently but still giving F.22 intermittently or every few seconds. So... I've been running the system with a chemical flush and it appears to be improving having run continuously all day yesterday.
Now, what I'm thinking is the automatic bypass valve might be blocked open giving rise to the premature burner shut-down and excessive cooling of circulating water as the bypass pike gets hot very quickly when the burner starts up.
So... when I drain and flush out cleaner I'll inspect auto bypass valve but there are 3 versions listed Presumably it's to do with the pressure at which the valve opens and I'm guessing is relative to the head the pump needs to pump to highest radiators?
150240 - AUTOMATIC BYPASS VALVE 2.5M 150242 - AUTOMATIC BYPASS VALVE 1.7M 150243 - AUTOMATIC BYPASS VALVE 3.5MBoth shop and flat circuits are opened/closed by 2 port valves but the shop circuit is permanently "open" and can't be shut down with call-to-heat, likewise the flat circuit has several radiators that can't be closed down by TRV's so I'm thinking the auto-bypass valve could actually be blanked off completely without any problems?
Obviously there's the questionable diverter valve which if the actuator is connected and someone turns on the hot tap the boiler instantly drops beck to F.22 but we don't need hot water and as the valve is ridiculously unreliable I'd rather just leave it disconnected.
Sorry for the long lost but if anyone has any other suggestions to try before venturing into the realms of changing the main PCB I'm all ears.
Cheers Pete