ever seen a blown cut-out fuse?

Drinking a cup of tea, Ipad in hand, suddenly I have a life size image of one of your thumbs and some of your fingers next to mine.


I have given mine a scrub up having finished work, otherwise very similar.


 Andy B.

Yes, we saw one a couple of months ago, caused by a builder not understanding that an RCD, despite being labelled '40A, 30mA' is does NOT contain overcurrent protection, basically leaving the shower protected by the 60 amp BS1361 in the service head.


Also being a builder, he hadn't torqued the terminals.  The result was inevitable... the terminal slowly charred, went higher resistance, got hotter still.. and over the course of 2 days, burned itself clear, whereupon it pressed the now bare live load wire into the earth sleeving.


Apparently the bang was loud enough to be heard from the shower (which was in use at the time). Customer called us out, we were able to fix the issue with a neat 18th edition compliant 2 way board with main RCD while awaiting the DNO's arrival (tails dead of course, due to the fuse failure)  Once again, SSE impressed with the speed of their response, despite knowing it wasn't an emergency.

I was told a story about a time when a cut-out fuse blew then the homeowner removed the fuse carrier and inserted a trowel across the contacts of the service head. It arced and the heat spot welded the trowel to the contacts.

Even with radio teleswitches, start times for economy 7 or similar off peak tariffs are somewhat staggered. Mine runs from midnight until 01-00, then full price from 01-00 until 02-00, then off peak again from 02-00 until 08-00.

My neighbours time are from 01-00 until 08-00. Another neighbour is from 23-00 until 06-00.


Staggering the "off" times is of much lesser importance than the "on" times. Considerable load is connected at the commencement of the off peak tariff, but relatively little is disconnected at the end of the allotted time.

A lot of the load is thermal storage space heaters and hot water tanks, these have their own thermostats which are often satisfied before the end of off peak hours. Likewise charging of EVs, most will be "full" before end of the off peak hours.

Kelly Marie:

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!

Hi Kelly


Guess that's a possibility. In the past I've lived in the city and a large village (3 doors down from the substation), and at both places the lights dipped noticeably at 22:30. Now I live in a rural location, where there's no mains gas. There are quite a few old folk in the village who've been here since the dawn of time, and must have had storage heating installed when it was on offer from the then area boards. At 22:30 the lights practically go out. You can set your watch by it!


This is one of the drawbacks with the radio teleswitch - they nearly all switch on at the same time, when they receive the timing pulse. The older mechanical timeswitches (manually wound, motor maintained) had a slight margin of error, in that the timing depended on the meter man's watch and his accuracy in setting the dial. This gave a few minutes' discrepancy between individual households E7 switching in, so the volt drop wasn't quite as obvious.

Once,


Lightning strike on a cottage I stayed at In NW Scotland.


All that was left of the cut out and fuse was powder and scorch marks.


Regards

Simon

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!

I have found many blown cut out fuses.

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.

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.


  - Andy.

Twice 


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