No such thing as Safe Isolation. You are only proving dead at the time of testing, a few seconds later the installation or part of it could become live.

Best thing is do not touch anything conductive even if it is green/yellow covered.

JP

John Peckham said:

No such thing as Safe Isolation. You are only proving dead at the time of testing, a few seconds later the installation or part of it could become live.

In addition, there's a far more fundamental issue in logic with the term "proving dead"... 'Absence of evidence is not evidence of absence'

It's not easy (some scientists and philosophers might say not possible) to 'prove' something is not there. In fact, all we are doing using a voltage indicator is saying 'I can't detect a sufficient amount of electrical energy can travel between the two points I tested to operate the detector'  It's very easy to show "false positive" by not making contact with the conductors we are testing between, and we know we have to check the voltage indicator is working before and after the test.

Sadly, we are not 'proving dead' but gathering as much evidence as we can that the circuit is likely to be dead.

And then, as John Peckham  said, 'proving dead' is a momentary indication of 'not energized' not a proof that your means of isolation are infallible for all circumstances.

So, you might ask, how on Earth (no pun intended) do I comply with the absolute duties of Regulations 13 and 14 of EAWR?

Unnervingly the answer is that (as HSE Memorandum of Guidance on EAWR tell us) Regulation 29 provides a defence against certain of the provisions of EAWR (including Regulation 13 and 14) for someone to prove they took 'reasonable steps' and 'exercised all due diligence' to avoid commission of that offence.

So, you do what you can, and use that as a defence if worst comes to the worst! Also shows that 'proving dead' alone, if anything were to go wrong, is also not a 'get out of jail free' card ... for example if the 'danger' could have been avoided by other means such as the use of insulated tools etc.

Perhaps JP offers good advice here ...

... Keep safe, mind how you go!

(It's a 'Thursday' post [general groaning])

Methinks that JP is teasing us. :-)

It should not be possible for the installation to become live if locked off and the key is in one's pocket (electricians' padlocks are sold with only one key), or perhaps the main fuse(s) is. That said, there is nothing to stop a malefactor from removing the padlock with a pair of bolt croppers, or putting in some other fuses. Were that to occur, the malefactor might struggle to avoid a charge of murder, but at least the duty holder could rely on R. 29 of EAWR 1989.

Methinks that JP is teasing us. :-)

It should not be possible for the installation to become live if locked off and the key is in one's pocket (electricians' padlocks are sold with only one key), or perhaps the main fuse(s) is. That said, there is nothing to stop a malefactor from removing the padlock with a pair of bolt croppers, or putting in some other fuses. Were that to occur, the malefactor might struggle to avoid a charge of murder, but at least the duty holder could rely on R. 29 of EAWR 1989.

Adhere to the five essential rules (PIPIC) for making low voltage equipment dead and safe to work on.

Evening Chris

Can you think of way and installation could become live with the main switch off and the supply fuses withdrawn?

JP

PEN faults, solar panels, batteries poor drawings - hands up if you have ever pulled the wrong fuse on a big site? There may be another incomer for something un-marked.

It is far from impossible for things to be live or worse for them to become live mid-job after all.

And then beyond that, the cases where it is meant to be. Live working may be OK, so long as you can justify it and have the tools and know how to do it well. Of course if not, then  you first slip-up maybe your last.

Mike.

Yes. There is more than one (mains) supply. I recall such an event being mentioned during my training, but not in a domestic installation.

But ...

There could be.

I am in the process of installing a new DB at home. The new one sits adjacent to the old one, but the supplies are different so there is scope for carelessness.

OK. As Mike says, a PEN fault. So next door is still connected and we share the same gas (or water) supply so neutral and earth go up to somewhere near line voltage. Hang on though - I could be touching an ECP without working on the installation.

But then again, both supplies are in plastic and we have no PV on the roof and no EV plugged in on the drive.

Hm?

Chris Pearson said:

It should not be possible for the installation to become live if locked off and the key is in one's pocket

Induced or capacitive coupling from another source (perhaps lighting ... but not always) has been known to take human life !

It's "energization" ...

Chris Pearson said:

There is more than one (mains) supply. I recall such an event being mentioned during my training, but not in a domestic installation.

But ...

There could be.

Island mode ... prosumers' electrical installations ... and other means of energization!

John Peckham said:

Can you think of way and installation could become live with the main switch off and the supply fuses withdrawn?

I can. Even without solar PV and battery storage ...

YES ... but ... that's only one option. And it's not just "PEN" problems. There are TWO other issues to consider here:

1. What if I said that "diverted earth currents" are not limited to PME, but possible in ANY system with main protective bonding?

2. The harmful current n may not come from a protective conductor, but a live conductor, or even a telecomms/auxiliary conductor?

Worth remembering that we don't need Amperes to kill, just mA !

Are we talking electromagnetic induction and conductive coupling when it comes to telecoms ?