I have a sealed water sytstem with a pressurised Megaflow hot water tank. Occassionally the system pressure just drops to almost zero for no reason and the boiler will not fire up again. I think its the water pressure switch that effectively switches off when the pressure drops but I don't know how to reset it. I've re pressurised the system to 2 bar but still it won't fire. Any ideas?

Jim Thomas, December 2009

It might also have overheated when the pressure was low (less water content, too much heat) I think that there is a reset button on these, its been a while. Red with a cross shape button push this in , you'll feel it click. Then fire it up

Mark gas engineer, December 2009