I have adequate CH but the DHW is not hot enough. (Luke warm is an exageration!) The lower heat exchanger has been flushed through and the PCB has been recently changed. Everything ran fine for a couple of days but now, when the boiler fires up, the flame drops right down. Any ideas?

Barbara G, December 2007

Not an answer, but just to say exactly the same problem with my Halstead Ace High. Also had same problem last year, and it sorted itself out (the morning of the day the plumber came, no less). He guessed it may have been hole in diaphram which pushes on the microswitch; other postings here and elsewhere on web indicate sludge build-up may also be cause...but I have a water softener. Another problem is with PCB - which I had to have replaced two years ago.

AndrewRH, December 2007