Faulty main 100A Fuse

[vwes59]

For some reason I'm getting the strange and unusual faults at the moment.

Got called a day or so ago to a tripping RCD. House is quite old and has a modern extension, so there were two consumer units. The fault appeared to be in the older board (I say older it was a board from 2015ish). Anyway I thought I'd test the RCD first. Plugged in my Kewtech tester, set it to do an automatic 30ma test and immediately got a warning that it was only seeing 8V, and very fleetingly 243V. Plugged in my plug tester and it showed that Line and Earth were reversed ! Now all the while I was doing this, the client was making a coffee which threw me completely as she was on the same circuit. Tried a different circuit, same results, wacky voltage and Line/Earth reversed. The just to add to the fun and games, the RCD tripped. So I turned off the power and went to try some dead tests, but my tester warned me of 8V, so refused to test.

It was at this point I noticed there was nothing displaying on the digital meter, so to all purposes there was no power coming into the property. Turns out, when Electricity NW turned up, there was a fault in the Fuse enclosure. The fuse hadn't blown as such. Everything worked fine when it was fixed.

So, my question is has anyone else come across this kind of fault ? Why was I seeing 8V whether the power was on or off, and why was my plug in tester showing a Line/Earth reversed fault.

 

[MJPD29]

Sounds like a poor or loose connection rather than the fuse being faulty.

 

[Deleted account]

Sounds similar to a fault I came across A few years ago. up front rcd tripping.

it was a real pain in the --- to find.

Did dead tests on all circuits no faults shown.

disconnected all circuits bar one. The socket circuit, RCD tripped. Assumption it was the socket circuit. So reconnected all other ci4cuits and left socket circuit disconnected. RCD tripped.

So I disconnected Each circuit one at a time and re energise. rcd would trip when load was applied each time.

did a Zs at socket, I was getting different reads each time.

I did Ze at board and could hear a slight crackling noise from somewhere as my multi meter

Turns out the crackling was from the incoming. W3stern power called, loose termination In head.

I never once suspected it would be the incoming fuse. I was making assumptions and working against myself. I really didn’t do a very good job of finding this fault as I had proven that the circuits where fine, but wouldn’t accept it.

first time I have come across this and the last. Never seen this since.

 

[Deleted account]

To add to the above it took me a full,day of pulling my hair out.

I was so embarased by what it turned out to be I admitted to the customer this and didn’t charge one penny.

I did get loads of future work from her and All her friends in future. Honesty does work.

 

[timhoward]

To add to the above it took me a full,day of pulling my hair out.

I was so embarased by what it turned out to be I admitted to the customer this and didn’t charge one penny.

I did get loads of future work from her and All her friends in future. Honesty does work.

These things happen, and its a highly unusual situation! Some of my best customers have arisen from the situations where things went a bit wrong.

I had one a couple of years back which defied all reason for far too long - I was only adding a spur to a ring final, and it was a friend of a friend (fatal!), and I'd promised it was a quick and fairly cheap job....I was in there nearly 5 hours!

Long story short - both ends of the ring were in different breakers so isolation was confusing, but one end did look like a ring as it had a radial in same breaker. Having sorted that, and IR tests passed, I lost continuity on the line that had been there a minute earlier. After far too long faffing around unscrewing sockets and head scratching I turned a FCU for a boiler back on (had turned off for IR test) and hey presto the continuity was back. Inside the FCU the boiler and incoming ring were together and the outgoing ring was connected to the load. So the 13A fuse had been part of the ring before! Unfortunately I'd had to split the ring and break it down to realise that I'd caused the break myself. But at least the issue surfaced.

I was looking fairly silly by this point, but luckily the customer understood the odds were stacked against me. I charged for 2 hours and later got an EICR out of it too.

So yes, honesty pays, even when you look an absolute clown!

 

[Darkwood]

I would check the terminal clamps are seated on the correct side of the cable or busbar pin, most modern quality gear has barriers to prevent the cable or pin been inserted behind the clamp but not all, just a common issue which unless you visually confirm can go undetected until it starts causing problems.