hi i've got a myson midas b. problem is that once i light it the hot water starts to heat up (as i have it on instant) but if not used cuts out,extinguishing the pilot light then i can't relight it untill i've drained all the hot water off through the taps. what could this be as i've already changed the dhw thermostat.

rich, August 2009

Clean the heat exchanger. The over-ride thermostat is cutting in. I would suggest that you clean the heat exchanger seriously. Also check the flue to ensure that ther are no extranoius products within.

townteck, August 2009

faulty dhw pump or blockage in the bypass. have a qualified engineer take a look, or better get it replaced as they are ancient.

Ian, August 2009