I have a Glowworm Ultimate Boiler, I've had it for around 12 years and just recently it stopped working. The boiler is in near constant use. I have a service contract with Scottish Gas, recently it just stopped working. Seemed to coincide with the bad weather we were having (may be a coincidence)

When the engineer came out he read through all the diagnostics on his PC, he said everything looked ok but it was quite possibly water that got in that had tripped the internal fuse (up near the fan). He replaced the fuse and hey presto everything was fine .... for a couple of hours .... bang it tripped again.

Call to engineer, they'll be out next morning ... afternoon arrives and then engineer has a look after me explaining what had happened. He replaces the fuse on the main circuit board and says it was probably water in there that was causing the problem so drys it out with a hair dryer and switches on. Fine .... for 3-4 hours and then .... bang it trips again.

Now to me (and I'm not technical about these things at all), this sounds like some wiring or electrical issue. I popped open the circuit board to look for any water and couldn't see or feel any! To me it's as if something is heating up and expanding and at that point is touching something else hence the 'bang' of the fuse on each occassion.

Any thoughts or suggestions?

Jason, November 2009

Not sure if this applies to your heater but I spent ages trying to find what was causing my Glowworm domestic boiler to trip the main circuit breaker intermittently. Eventually, I discovered the "fault": the flue exhaust above the flat-topped inner boiler housing was leaking condensation, which gathered on the flat surface, eventually creeping up to the small cut-out switch mounted there and causing it to trip. The water eventually evaporated, leaving no clue as to why this was happening. Quick fix - shield the cut-out with a ring of waterproof putty or similar but remember to CHECK FOR WATER BUILDING UP. Full fix - replace the exhaust gasket.

Arnold J. Bilgepump, December 2009

Update .... after arguing with Scottish Gas to get an engineer as they didn't attend they finally sent one out. The engineer apparently replaced the fuses switched on and it blew again, he then took off the gas valve and replaced the fuses and hey presto it seemed to work. His assumption here is that it's the gas valve that's causing the problem. He's coming back later hopefully today to replace the valve.

I realy need some experts to tell me that this is a possible reason that it would trip the fuse.

Jason, November 2009