ok you guys are not gonna believe this but my Dads swiftflow 80 combi's decided to pack up now. it fires for about 4 mins then turns off, I thought pump, but he says the rad furthest from the boiler is getting heat. the hot water is not working at all.
my other thought is blocked heat exchanger, as he hasn't been keeping the system correctly dosed.
my other thought is blocked heat exchanger, as he hasn't been keeping the system correctly dosed.