Elfin Safety gone bonkers

What if some part of the service head disintegrated as he pulled the fuse and made a short across the incomer, protected only by whatever fuse is out in the street/substation?

Indeed. Some of those fuse carriers have been known to fall apart, too.

When someone I know (ahem) fitted a DP 100A isolator, they togged up just like that.

And turning off the consumer unit would not isolate anything he was working on.

Clearly not as much as you think. He was taking adequate precautions against the fuse carrier/fuse/cut-out falling apart when he pulled it.

Well now you know how to do safe live working :-)

It may not apply to your install, but there is a short circuit risk with some fuse carriers[1]. So depending on the earth loop impedance and the capacity of your substation transformer, you could be into arc flash territory, and the associated explosive short and spraying of molten metal about.

So its got to be simpler to take the relevant precautions rather than spend time investigating the exact circumstance of every install, since its little extra effort.

The old metal clad incomers with ceramic fuse carriers in particular can end up pulling the incoming live onto the earthed casework should anything fall apart as you pull the fuse.

The main fuse is before the consumer unit.

I did read that the Sky engineer now has to screw the top of his ladder to the wall when fitting a new dish. Dunno how true this is. But, there would be nobody on the ground to hold the ladder if it slipped. In a past life and as a contractor I mounted 4 steps of a ladder in a chemical factory - 2 more steps to go. I was gripped by the big cheese and told not to go any further as I would get cancer. He was dressed up like a spaceman and asked me to the same. I waited until he has gone and went up the further 2 steps. I suppose that he was doing his job.

I have worked on live 3 phase, which I thought had been isolated: I had all the main fuses lying on the work surface in front of me. There was an additional link to the incomer that 1) I didn't know about and 2) shouldn't have been there that had been added by a cowboy in the past. It was following safe working practices, such as those, that saved me from even knowing the parts were live until later.

I was thinking about some massive inductive load inside the house, but apparently I should have thought of the fuse holder falling to bits and splashing molten metal about.

I did ask him whether he or his colleagues had ever had a large flash, and he said no they hadn't. However, I agree that with even a tiny possibility of the fuse holder vapourising I'd take precautions too.

The Eon man's precautions only protected his face and lower arms. Apparently, branding your chest with molten metal (he was just wearing a T shirt) is a sign of machismo.

An old mate of mine did the forensic investigation after an accident where someone was standing on top of big 11kV cables in a cable tray in order to fix something to the wall above. This was enough to breach the cable insulation. It was not a pleasant job.

There was a similar very sad accident in the North Midlands a few years back where apparently a young and inexperienced manager had been left in charge of a substation and someone was sent to work on some fairly high voltage plant which had been switched off, but other cables that crossed his position had not been switched off. That was what the newspaper said, anyway, I never saw an official report.

Maybe he used to be a drain unblocker? Brian

Well, if that were the case why don't all these folk tog up this way, and they don't! Brian

Friends jack russell has rolled in some fox poo, so send him round to the so-and-so and give it a bath in some bleach.

The dog that is.

If you buy stuff from aeriels and tv they sell these eye bolts and recommend their use.

Arc flash protection. Here are some videos:

I can see the need to do this with some old installations but is it necessary with current designs of main fuses?

If you have the gear to hand, why would you *not* do it? It must be all of 20 seconds extra to put on the gloves and visor.

The main issue here is the unknown unknowns... These guys are quite often trained to do the specific job safely in *any* situation. So its far simpler to have a one size fits all procedure, that does not require detailed knowledge of the installation, or the upstream supply, and does not need any great experience or knowledge of electrical installations and how they might be molested out in the wild.

So yes you might be able to look at the style of cutout and be fairly certain that its unlikely to short when you pull the fuse, and you can see there is no load at the CU, hence you assume "low risk". However are you *sure* that someone has not hacked about with the cutout - say to try and illicitly power their grow room at some point in the past? Or that someone has not wired an additional submain feed to another CU at the incoming terminals of the main CU, so that turning it off, still leaves attached loads elsewhere?

Maybe not, but it'll be easier for their "stock" method statement to say always wear PPE when pulling the main fuse

You are discounting human factors. The probability of a modern cutout failing are low. However the probability of a person mistaking a fragile old cutout for a new, probably inherently safe one are much higher.

The donning of the correct kit also creates the impression of a professional outfit, rather than a bunch of cowboys, and also sends a subconscious message: "don't f*** with the meter wiring".