[retrotecchie]

A neighbour phoned me today in a bit of a panic. Her electricity had tripped and she couldn't get it to come back on again. So I walked up to her house and within a few minutes narrowed down a N to E fault tripping her RCD.

First obvious question. Have you plugged anything new in, or has any appliance been playing up?

She'd moved her tumble drier. The cable was too short, so she'd used an extension lead, only it was an old roll-up lead on a plastic reel from which she'd just pulled out the two feet she'd needed. When I picked up the reel, it was hot and starting to melt. I pulled off a few more feet of cable to find that the insulation had melted on the cable itself and in several places wires had touched. There was the N-E fault. Had the wires not shorted out, my guess was the reel was maybe only minutes, maybe just seconds from catching fire.

I'm asking you to all PLEASE...Make sure your leads are in good order, with an appropriate cable and correctly rated fuse. Never EVER under ANY circumstances use a reel type extension for any high power/heating appliance without unreeling it fully first. If the cable gets hot under load, having it rolled up will concentrate the effect.

In this case, my neighbour was lucky as the N-E fault tripped the RCD and shut the power off. Chances are, the reel could easily have ignited. In my opinion, she was only minutes away from that happening. I just want you all to have a safe and happy Christmas/Yule/Hanukkah.

[JoeSoap]

@retrotecchie
Good advice 👍

[retrotecchie]

@JoeSoap

Not kidding...when I said the reel was melting, I mean actually beginning to drip plastic. I'm not exaggerating when I say that was a fire within a gnat's whisker of igniting. The tumble drier was in the utility, and she was watching TV in the front room at the other end of the house, with two intervening doors, until the power tripped. If the RCD, which was only installed as a retrofit about five years ago, wasn't there or hadn't worked, could have been a different outcome.

[JoeSoap]

@retrotecchie
Great device the RCD 👍

[Plantagenet]

@retrotecchie

Reminds me of the 9 KW shower installation i came across whilst doing some unrelated work in a roof space, hooked up to 4 mm twin and earth cable covered in 200mm insulation with a decent length of run,Shower purchased from one of the ‘ sheds ‘ as a replacement for some old vintage 6 KW unit. Me,“you had best get an electrician in to upgrade your shower cable and MCB .” Indignant reply “well it’s been ok during the Summer.”

[retrotecchie]

@Plantagenet

In a previous life, I'd come out of the house one snowy winter morning to see my half of the roof completely white and snowbound, and the other semi's roof absolutely clear, just damp. For gag value, I borrowed a FLIR thermal imager from work and had a look that evening. You could see how effective my insulation was compared to theirs, but you could also make out the heat signature of cables running through their roof space, plus a couple of other hot-spots.

Judging by the occasional whiff of ganja emanating from the teenager's bedroom window I suspected a high intensity grow light or two. Nope...the older lad, mid 20's had converted the loft space into a gaming room with his computer setup, and was running a 2kW fan heater up there to keep warm.

[Plantagenet]

@retrotecchie
Nice one, I used to love all that, "I"ll just have to pop up in your loft for a look ." " Oh hang on I ve got some stuff up there that needs covering up before you go up ." ( I've worked in some dodgy areas)

[Beki]

A neighbour phoned me today in a bit of a panic. Her electricity had tripped and she couldn't get it to come back on again. So I walked up to her house and within a few minutes narrowed down a N to E fault tripping her RCD.

I remember you saying you had some leccy quals? What does this mean in non-sparky language?

[retrotecchie]

@Beki_EONNext

HND in Electrical and Electronic Engineering.

Several 'professional qualifications' back in the day, but now lapsed as I don't need 'em any more. I came 'off the tools' in 2013.

Still hold a current ECS certificate for carrying out electrical work on construction sites.

I am considered a 'competent person' under Part P of the building regs.

Oh, you mean the fault?

Ok, a RCD is a Residual Current Device. It measures current flowing in both the Live and Neutral cables. If it detects an imbalance, i.e any electricity going where it shouldn't then it trips for safety. In this situation, where the extension lead had burned out, instead of all the current going down the Live, through the appliance, and an equal amount of current going back up the Neutral (in balance), some of that current was shorting in the extension lead down to Earth and not making it back to the RCD. Imbalance, thus tripping.

If, however the fault has been Live to Earth rather than Neutral to Earth then the fuse in the plug might have blown, or a circuit breaker feeding the socket might have tripped.

Chances are a sudden short circuit blowing a fuse or tripping a breaker would also trip the RCD, but they have a certain time delay (100mS usually) and a minimum difference they can detect (0.03A).

Bottom line, in non-sparky speak? She was exceedingly lucky not to have a serious fire.

[Beki]

@retrotecchie My hubby is an electrician in the Army, but he loathes it! 😂

What does the N to E fault in RND mean?