When electrics go wrong!!!

[MaintenanceSpark]

The terminal screw looks to be well down the thread compared to the other one. Did it miss the cable completely?

2 strands of the cable were longer for some reason so the other 5 had never been clamped down by the terminal screw!

 

[timhoward]

View: https://youtu.be/B7CUw885b7g?feature=shared

 

[timhoward]

Thought you would enjoy this one:


A new extension was built which needed a new CU. The problem the builder faced was the Henley block was full.
No problem, remove the tails that feed a switched fuse and SWA for static caravan and connect his screwfix special there.
Then sacrifice his RCD plug extension lead, and connect the flex into the switched fuse and plug in it into a new socket.

The static caravan had a hot tub, a tumble drier and several fan heaters.

 

[lozarus]

Seems the most approiate thread for this - a quick reminder in always proving dead!

One of the more interesting jobs i was issued involved going inside a building that had been closed down & boarded up for about 8 years. Naturally it had been broken into a fair bit, fires started, undesirables generally trashing the place and the inevitable metal theft. Bear in mind everything had been smashed or destroyed in some way. No obvious signs of power - no lights (the few that were left intact) or such on. I came across one of the boards, with the remains of the singles that had been cut off by the metal thieves hanging out of it and could so easily have just shoved my hand in there....but decided to offer a volt stick up to it before getting the probes out....and yep - all live! Quite how none of those cut ends had come in contact with each other I'll never know....

I ended up finding the intake room and disconnecting each of the supplies to the boards, then the DNO came and removed their fuses.

The interesting thing is, they can't have cut through the cables, and them remain live - if nothing else breakers would have tripped. It was almost as if they'd cut through the cables and then turned the circuits back on again! Maybe a nasty trap left. Who knows

Anyway - don't assume. Always prove dead even if it seems unimaginable that it could still be live

 

[littlespark]

Although very handy, those light pens can give false positives…. Or rather a true positive, but just very very small voltages. Nothing near 230

Some ghost voltage on a neutral or cpc?

I’ve even had them light up held against a tiled wall a few feet away from where a cooker hoods fixing screw had been screwed in between the neutral and earth of the supply. (Diagonally chased up to the hood)

 

[lozarus]

Although very handy, those light pens can give false positives…. Or rather a true positive, but just very very small voltages. Nothing near 230

Some ghost voltage on a neutral or cpc?

I’ve even had them light up held against a tiled wall a few feet away from where a cooker hoods fixing screw had been screwed in between the neutral and earth of the supply. (Diagonally chased up to the hood)

Indeed. This one in particular goes off with a 9v battery!

By this point I'd already confirmed it was live with probes - this was just a more visual way to indicate my point - it wasn't possible to film whilst holding my approved voltage indicator!

 

[sunray]

I always think these things are unreasonably maligned. Yes I agree they can give unexpected results but like any tool they need training/experience, one wouldn't expect a total novice to pick up an arc welder and make a perfect weld without some sort of tuition or experience.

 

[TimJ01]

This definitely went wrong for my mate yesterday. He got a call out for an RCD tripping in a shop so went to have a look, managed to fix that fairly quickly and whilst he was there they said can you have a look at our lights so he did. It was a grid ceiling with 600x600 LED panels in, and the way they were wired was with a plug/socket type affair on short leads and T-pieces. The name of the plug escapes me for now but its a flat 3 pin plug same as these.

View attachment 110999

You can get short leads with electrical rewiring male plug on one end and a female socket on the other you then use 3/4/5/etc way splitters like above to give you ways for the lights which obviously have a male plug fitted. We fitted loads of them the other year on shop refits, I didn't like them as you couldn't really support the cables between the lights and they just ended up on top of the grid, also they were really hard to push together and engage the clips and sometimes if you pulled them apart it broke the T-splitter instead exposing the pins.

Anyway, some of the lights weren't working (not one of our jobs by the way) so he goes into the grid ceiling to have a look, grabs one of the leads at a junction and gets a big electric shock, falls off the ladders, cuts his leg and twists his knee quite badly. Turns out that the T piece had melted and exposed the connection, probably because it was never fully pushed together. He's been to A&E today and they said he has probably damaged his ligaments.

So not too sure who is at fault really, I suppose by the book he should have turned the power off, locked the MCB off and got the barriers out, tested dead etc etc but when you are fault finding like that you really need to do it live in order to find where the live bit ends and the fault begins, which he certainly did do yesterday. Or is the shop at fault for letting someone near their dangerous electrics? I'm not too sure how the shock was that bad but he reckons he thought his number was up and can't remember falling off the ladders, just getting up off the floor. He was on fibreglass steps, boots and carpet so it wasn't that, must have been the ceiling grid that was earthed, either that or it just wen't between the pins in the plug via his hand and he was being over dramatic about the shock to justify falling off the ladders.

A bit of a drama queen throwing himself off the ladder did you ask him why you jump off like that when it wasn't a big shock?

 

[Sparkgap]

Generally, I've been pretty lucky with the incoming supply at home. The only failures in the past 25 years have been a single phase HV loss to the substation in the garden (tree branch), full HV loss to substation (HV connection to transformer) and the overhead distribution on the pole in the road (old CI joint box on pole blew up!).
Had some interesting effects with the first one: with the single phase loss I found I was getting about 85V on the mains, so decided to see what would work at those voltages. GLS lamps: nice rosy glow. LED lamps: some work, some don't. Kitchen DAB radio: works! It seems lamps with switch mode supplies (and the radio) are quite happy at the lower volts while those with dropper circuits aren't.
With the other two we had to be connected to the overhead lines around the corner while NP sorted out the transformer conns. With the replacement of the blown joint box they found the pole was so rotten it would have to be replaced so we were hooked up to the other lines again. In both cases I was now at the end of the line and at times my supply would drop as low as 178V!

 

[Sparkgap]

View attachment 120671

Seems the most approiate thread for this - a quick reminder in always proving dead!

One of the more interesting jobs i was issued involved going inside a building that had been closed down & boarded up for about 8 years. Naturally it had been broken into a fair bit, fires started, undesirables generally trashing the place and the inevitable metal theft. Bear in mind everything had been smashed or destroyed in some way. No obvious signs of power - no lights (the few that were left intact) or such on. I came across one of the boards, with the remains of the singles that had been cut off by the metal thieves hanging out of it and could so easily have just shoved my hand in there....but decided to offer a volt stick up to it before getting the probes out....and yep - all live! Quite how none of those cut ends had come in contact with each other I'll never know....

I ended up finding the intake room and disconnecting each of the supplies to the boards, then the DNO came and removed their fuses.

The interesting thing is, they can't have cut through the cables, and them remain live - if nothing else breakers would have tripped. It was almost as if they'd cut through the cables and then turned the circuits back on again! Maybe a nasty trap left. Who knows

Anyway - don't assume. Always prove dead even if it seems unimaginable that it could still be live

Back in the 80s I went down Monkton Farleigh ammo depot which Trowbridge college students were restoring electrics to the various areas to open as a tourist attraction. For supply security back in WW2 the depot had two incoming supplies feeding two separate substations underground which also fed the local villages. After the place closed there was an incident back in the 70s where the supply to one village failed. On investigation the power co. found the burnt remains of an axe embedded in one of the HV incomers. No sign of the hapless copper thief though I expect he had run home to change his underwear! Interestingly, there were a lot of switchgear failures the students had to sort out: MIC cables into switchgear, cold damp underground passages, condensation drips down cables and into switchgear and BANG!

 

[Simon47]

It seems lamps with switch mode supplies (and the radio) are quite happy at the lower volts while those with dropper circuits aren't.

That's not surprising. These days, many SMPSs are wide range - I think I recall seeing as wide as 90V - 265V. There are downsides* - but from the manufacture PoV it simplifies stock management to have one supply for the whole world instead of several for the different voltages to be found.

* The main one being that the device has to be designed for the maximum current (min voltage) and max voltage. For "big things" that can put the cost (and size) up substantially, but for something small, the difference in cost for the few components affected is minimal.

 

[sunray]

Generally, I've been pretty lucky with the incoming supply at home. The only failures in the past 25 years have been a single phase HV loss to the substation in the garden (tree branch), full HV loss to substation (HV connection to transformer) and the overhead distribution on the pole in the road (old CI joint box on pole blew up!).
Had some interesting effects with the first one: with the single phase loss I found I was getting about 85V on the mains, so decided to see what would work at those voltages. GLS lamps: nice rosy glow. LED lamps: some work, some don't. Kitchen DAB radio: works! It seems lamps with switch mode supplies (and the radio) are quite happy at the lower volts while those with dropper circuits aren't.
With the other two we had to be connected to the overhead lines around the corner while NP sorted out the transformer conns. With the replacement of the blown joint box they found the pole was so rotten it would have to be replaced so we were hooked up to the other lines again. In both cases I was now at the end of the line and at times my supply would drop as low as 178V!

Several years ago Mrs Sunray complained the pans had gone off the boil mid cooking dinner, the fluo lights had gone out but LEDs were still on, I checked mains, we had ~80V L-N, 240V L-E. we had lost N at the sub.
We finished the cooking on the camping stove and sat to eat with a table lamp and the TV running on an inverter/leisure battery. By then the power had gone off completely.
The funny thing this was a younger neighbour visiting to ensure we were OK and seeing us apparently nornally seated eating.

 

[Simon47]

We finished the cooking on the camping stove and sat to eat with a table lamp and the TV running on an inverter/leisure battery. By then the power had gone off completely.
The funny thing this was a younger neighbour visiting to ensure we were OK and seeing us apparently nornally seated eating.

I think that's going to be one of those generational things. Some of us are old enough to remember the 70s and aren't fussed if the power goes off. I suspect a lot of younger people wouldn't know what to do to pass the time if the power (and hence internet etc.) is off.

 

[littlespark]

We’ve got candles, camping stove, blankets… and nowadays, solar power banks, and a battery storage system in the house that can be used for freezer if needed.

 

[mickegh]

We’ve got candles, camping stove, blankets… and nowadays, solar power banks, and a battery storage system in the house that can be used for freezer if needed.

I've got the phone charger in the car and a couple of headlamps
Did me for a few days on a recent power cut
Don't keep much in freezer
Have an under/overvoltage protection relay i might fit to main board