Most difficult fault

[Judd]

Just wanted to know out of curiosity difficult wiring faults people have come across in there careers? what type of fault, and how you got to the bottom of it,
Some faults are easier to find than other, maybe the fault was an emergency call out or perhaps something that was picked up on a EICR,
I came across and neutral to earth fault that threw me a bit the other day,
Look forward to hearing your replies.
Lou

 

[Des 56]

Deviating slightly off thread because this one was extra easy to find

Very large bedroom which had 2 sockets on each of 3 walls
A young just out of his time chippy then fitted his skirting board

With a ring fault narrowed down to this bedroom,I wonder where he got the idea that right smack below the sockets was the best place to drill and screw

Only 6 fixings he made,yet he scored a bullseye on three socket cables
He's probably still out there playing his game of darts because I didn't get the chance to meet and throttle him

 

[Octopus]

About 6 years ago I had a client with irregular nuisance tripping - up front 30ma RCD, so the whole lot went off. This was a 16th century cottage with 3 extensions done by bob the builder.... or Stevis Wonder!

There appeared to be no pattern to the tripping, except the client thought that "snow" was a common dominator.

Over Xmas things went from bad to worse and they struggled to cook xmas lunch

So they asked what would help them - RCBO board - so that was fitted a couple of weeks later ...... so now only 1 circuit would go off.

Sure enough a couple of weeks later they called me to say the kitchen lights were the "issue" - but not on switch on ..... irregular but some time later

IR this area, removed lights ........ they had 3 x lights with multiple GU10's on a vertical poles fixed to the ceiling..... removed each in turn and discoverd that one of them had "rust" markings at the top GU10 ............... was it condensation from cooking? a leaky roof?

They decided they could do without the missing fitting of the 3 and the circuit never tripped again.

Fortunately for me the client was understanding, patient, and had money ........

I continue to work in said house now, for the new owners.......

 

[ipf]

Had a bad IR reading on a 16a 240v commando socket outlet, disconnected the cable and it tested fine and the socket outlet tested fine. Tested the breaker and it tested fine but as soon as everything was reconnected back to the bad reading. Re-terminated everything and still a bad IR reading. Told the other spark at shift change and he spent ages doing the same as me but couldn't get his head round it. I'm back on shift the next day and think I will have another go, tested it all again several times and just couldn't get my head round it. Went for a cup of tea and a smoke and by the time I got back the fault had disappeared. Every month when I get back onboard the vessel I test it and it has just disappeared.

Just can't get my head around this one and why it disappeared

Was that vessel the Marie Celeste, by any chance?

 

[ipf]

my own house. 15 years old and not touched since built on an estate.
I put some extra sockets in, extended ring etc. took a quick ring continuity neutral and earth all good. nothing on the live. traced it to inbetween 2 sockets. looked at the skirting and noticed a nail below the socket, so thought I'd give the cable a little tug and hey Presto. either it wasn't tested upon completion by sparks ( local cowboys) or it was tested before skirting were fitted

also ha phantom faults with seem to disappear and reappear. funny old game we work in.

Intermittent faults you mean?

 

[brianmoooore]

Customer reported very intermittent RCD tripping, which would trip again if immediately reset, but after a couple of minutes would be fine.
It only happened during the day, and of course, IR testing produced no clues.
Several visits later, I got lucky while there doing some other work, and the RCD tripped. Quick IR test showed a rapidly disappearing E-N leak on a RFC serving the utility room and garage.
Culprit turned out to be a large chest freezer in the back of the garage with a light built into the lid. Ice had built up in the enclosed bulb compartment, and when the lid was lifted, bulb was switched on, and would melt a little of the ice. The resulting water was running down into the bulb's base when the lid was closed, sometimes causing a E -N leak sufficient to trip the RCD, but of course, with the bulb off again, the water rapidly turned back into insulating ice, destroying the evidence.
All that was required to effect a cure was a quick defrost of the offending lamp compartment.
Because of it only rarely happening, and the several minute delay between the freezer being opened and closed, the customer had failed to make any connection between opening the freezer and the tripping.

 

[WillWX]

Most annoying one I've had, intermittent tripping of RCD.

Went round the same day and tested, everything was fine, hadn't tripped since the early hours, I put it down to perhaps a faulty appliance of some kind.

The couple unplugged a load of appliances and we left it overnight, the next morning I got a call to say early hours it was tripping out again. It would trip once or twice, then be fine.

So went back that afternoon, psychically looking at all socket outlets, and I just happened to notice a slight bit of charring and a purple screw on a double socket in the office, I unscrewed the socket and it was a full blown ants nest in the back box, never seen so many little sizzled ants, they must've been coming back in early hours and groups of them were getting fried.

Cleared it all out and sealed up inside and outside, never a problem again.

 

[jackhammerJIM]

So they asked what would help them - RCBO board - so that was fitted a couple of weeks later ...... so now only 1 circuit would go off.

Thats a very expensive fault finding method

 

[Octopus]

Thats a very expensive fault finding method

Having an upfront RCD is never a good idea, yet I still come across recent installs in this way....

When the decision to go for the RCBO board was made it was with the full knowledge of the client that it wouldn't fix the problem..... But would minimise the inconvenience ..... At that time and going forward ....

Role on the 18th and its daft ideas about RCD's and earth leakage design ...

 

[jackhammerJIM]

my bad i didn't read upfront rcd ...