A mate asked me to work out why his powered flue gas fire was no longer working. The setup is an inset style coal effect gas fire with an input of about 6.2kW. It has an add on powered flue fitted since it sits in a fake chimney breast that does not have a real chimney above.
The lighting procedure was to turn on the flue (via a switched FCU beside the fireplace), then go through the pilot lighting sequence using the control on the fire. First obvious problem was the flue was not powering up. I am not sure how the ignition inhibit between flue and fire works, although I assume that there is one, since it was not possible to even light the pilot.
I took the external box apart and found a blown internal 20mm glass cartridge fuse. Replaced it with the spare conveniently cable tied to the inside of the box! reassembled, powered it up and it sprang into life again. Was just about to try lighting the fire when the flue stopped again - presumably having blown the new fuse. It was late, dark and cold, so we suspended deeper investigations until later. (Alas, I was not able to locate a make or model number on the flue)
So, any suggestions for typical failure modes and diagnostic procedures for these things? The motor/fan sounded like it was spinning freely when it ran briefly. My initial plan was to measure the current consumption as a starting point to see how far from the fuse value it actually is.
One issue I did notice however was that the mains voltage at the time was very low (about 205V - which apparently is common in the evening in his neck of the woods). I presume these units have induction motors to drive the fan, but would they typically fuse them with so little margin that the current rise caused by a low supply voltage would take out the fuse?