Perhaps I've had a sheltered upbringing, but it's occurred to me that I've never encountered a blown cut-out fuse (e.g. a BS1361 BS88-3). So have any of you seen one? How rare are they? Any interesting or salutatory tales to tell?
Not a DNO cut out, but a private submain termination on campus about 35 years ago, a set of 3 100A fuses after someone drove over and tore out what is best described as a 3 phase extension lead direct from the building incomer to supply an outdoor theatre installation.
A very noticeable bang, despite not actually being in the building at the time but stood outside.
Almost an equally load exclamation when my 'repair' to get it back on again quick, that involved 3 short lengths of twisted fuse wire shunting each blown fuses was discovered, seriously denting my relationship with the site electricians.
Almost an equally load exclamation when my 'repair' to get it back on again quick, that involved 3 short lengths of twisted fuse wire shunting each blown fuses was discovered,
Yes, I've seen dozens over the years. From 30A rewirables to 100A HRC. The lower rated ones were nearly always caused exclusively by load issues - eg husband in the shower, wife puts the kettle on and the fuse blows. Higher rated ones (60A HRC to 100A HRC) for several reasons - customer's wiring faults, overloads etc. Overloads often happened at 22:30 when the off-peak kicked in and an extra 60A of load appeared on top of whatever the household was using (you may notice your lights dim slightly at 22:30 every night, as the additional load of storage heating is switched in - you'll be looking out for that now!)
I got called out by a plumber who thought he had blown the main fuse. I was able to confirm he had.
He was fitting a aluminium shower screen when part of the frame went behind an extractor fan and went bang.
I found he had drilled one of the frame screws through a concealed cable running diagonally across the wall he had tilled which made the frame live when he started fitting it, when he pushed it behind the extractor it contacted the earthed metal frame. The old 32A Wylex MCB did not trip but the main fuse did.
What was more worrying is what would have happened if he had not pushed the frame behind the extractor.
Later when fitting a new RCD protected CU the overhead supply pulled a massive lump of masonry off the chimney when a tree branch fell on the OH line a few poles away.
I have come across two blown main cut out fuses in domestic situations that I remember. The first in Milton Keynes. The customer had drilled through a ring circuit final cable buried in a wall. I don't know if the fuse was heavily loaded at the time, but it was winter and the time of day was evening.
The second fuse that had blown was in Norfolk. Again this was due to a drilled through cable in a wall. I seem to remember that it was also a ring final 2.5mm2 T&E cable. This was in the late morning in a small family home.
I renewed both fuses myself due to the urgency of the situation..
first was a diyer had changed their own consumer unit and connected the meter tails up the wrong way round and took out the cut out fuse, I didn’t see it happen but the fuse was definitely blown on inspection...
on a commercial sight a sparks got his phases and neutral all mixed up and when he threw the main switch was a loud bang and took out a main fuse
Once - many years ago in a Church. Someone decided that it would be nice to have all the schoolroom wall-mounted radient heaters on at the same as a service in the main church - the 60A rewireable cut-out gave up just as the service started. I remember the Electricity Board electrician twisting two strands of 30A fusewire together to improvise a 60A element.
Another more recently where the cut-out melted and went open-circuit, but the fuses themselves did remain intact.
Some due to faults, a short on a 32 amp circuit may take out the cut out fuse.
Others due to simple overload.
One recent one was a 20 amp cut out, though fitted with a 25 amp fuse. The fuse was not blown when inspected, but the presence of a box of spares suggested regular replacement.
Another recent one was a local farm, the 100 amp fuses in the 3 phase cut out blow "regularly" I was asked to supply "stronger" fuses but declined. Milking machinery and electric showers to blame. I suggested a supply upgrade, or a coal boiler for hot water/central heating.
Hi Warren I looked at the lights around 22:30 last nite and noticed not a flicker not even the tiniest amount of dimming I guess economy 7 isn't popular round here!
