Not sure you will find words like 'lock off' or even 'dead' in the big book - partly because sometime there is no lock as such but an equivalent safe method of work, such as removing fuses or links, or access control and tokens, and then there are cases which may, but only when reasonable to do so, include working with live conductors exposed, but in a well planned system those should be very rare and logged.

I am aware of organizations that mandate 2 man working for such cases, and require that both parties agree and record that they cannot see any alternative non-live way of working for the problem in hand - usually called up for testing and debugging machinery like generators with the covers off. Equally the DNO send one chap in to do a live change of a company cut out and fuse and no-one blinks, though street joints are at least two working.

Mike

With BS7671 being the primary book of reference for
Electricians
Designers
Testers
Especially in a domestic capacity and that it is a requirement for all to have (some CPS Competant person Schemes ask to see the up to date copy on the yearly assesment) an up to date copy. Surely this would be an appropriate place to have the subject matter of
Prove dead
Safe isolation
Lockoff/Lockout
GS38 compliant testers.

After all the main point of the rules (BS7671) and laws (EWR1989) is to protect the safety of person, livestock and property.  In my eye when a electrician is working on a CU/DB they are covered by the EWR1989 and BS7671 hence the safe method of work would include the list above.  Maybe it's a disscussion worth having?

I'm not sure that it is you know, it is a standard, but it is not intended to be used as a text or reference book -  by which I mean I challenge anyone with no prior knowledge of electricity to take it to bed one night and wake up understanding anything useful after reading it.

For that there are codes of practice, on-site guides, makers instructions and more text books than you can ever read. Also it has to cover anything from 100A single phase domestic with 6A lights and one ring, to large warehouse and barns,  to factories with 690v three phase machines passing by universty campuses and estates of industrial units on the way. Also it is not UK specific so ECSQR, EAWR etc do not always apply when '7671 may. It's also why we assume cable buried in a desert, even thouhg in the UK it usually isn't.

As it is folk get hung up about the fact that the cable rating annexes have not considered all possible installation cases and things like that - which given who writes it, is unreasonable. The person who understands any given installation intimately is the design authority.

Mike

Sergio Fernandez said:

Question. In BS7671 what reg states about proving dead? Also about locking off?

None, although there are provisions (via a long list of Regulations in the standard) to ensure suitable devices for safe isolation are present.

The reason is that BS 7671 provides requirements for electrical installations, not a code of practice or requirements for working safely on electrical installations. It is also not a design manual for electrical installations.

The standard you're looking for if you want to know the requirements for safe operation of and general safety precautions for work on electrical installation is BS EN 50110-1 (along with BS EN 50110-2).

Where you have electrical test equipment setups, BS EN 50191 also applies.

131.2.1 (i) provides a sort of framework for safe practices.

(131.2.1 (ii) has a typo, n in wrong place.)

Electricity at Work Regulations- Regulation 13.

www.hse.gov.uk/.../hsr25.pdf

That certainly covers locking off, but it assumes that the equipment is dead, however proved.

I shall stick my neck out and say that if you know that an installation (or part thereof) is dead, it does not need to be proved in the time honoured way with a lamp and proving unit. That said, if you are not absolutely sure, it would be foolish not to do so. I do not think that we need regulations to tell us that.

ETA: I have now had a quick shufti at BS EN 50110-1:2023 and it seems that the above is in breach of 6.2.4: "Verification of the absence of operating voltage shall always be completed prior to commencement of work." (My emphasis.) You can debate whether, e.g. removal of the company fuse(s) amounts to "verification".

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.