In my view, if the board is live, then two workers are required.

Remember though that working "on or near" live equipment is strongly discouraged, though not totally prohibited. IT MUST UNREASONABLE in all circumstances for the equipment to be made dead,  and REASONABLE IN ALL CIRCUMSTANCES for it to remain live.

In practice, and again in my view, it also depends on the nature and complexity of the work. Connecting a new subcircuit to a spare MCB that is turned off, but whilst the rest of the board remains live ? Possibly just acceptable. Removing an MCB from a live busbar and installing a new one ? Probably not acceptable. I have done this but cant recommended that others do so.

The rules need to be applied with common sense, and in particular what is meant by near.

Firstly I am no H&S Expert. I am, however,  a QS and do have a team. I am also the director and responsible person. In the event of an accident it all comes to me and the Health and safety executives prosecutions of me AND my company - So my thoughts are:

1) I think you're in for a health and safety finger pointing session coming up. 

Working in a live three phase DB will always carry a risk; More risk than a dead three phase DB.

As a manager (or QS) for my team, it's probably my job to create the safest working environment for my team that I can. 

The business risk and personal risk, working in a live 3 phase DB when written down, will scare the life out of anyone, and that's what the ol judge will see and decide on.

We're electricians - and we cant eliminate risk altogether, but a dead board will always carry less risk than a live DB.

2) Having said all the above, the reality is often very different; I've spent my life in and around three phase DBs, often in an office and plant room environment and fully support that modern DBs minimise this risk just by their very construction and it is fairly safe for an experienced electrician to work in a three phase DB that is live, to install another circuit for example. An older three phase DB with exposed bus bars and no incoming supply covers would be a completely different storey. 

We do work in modern three phase live DBs all the time, because the reality of turning off a large three phase DB or MCC that is supplying software or start up processes - even as "simple" as the door entry, fire alarm or fire alarm interface, smoke fans, or even just that the CCTV screen needs a password when it boots up, so that the security guard can see the CCTV and who knows what the password is........can add endlessly silly out of scope job costs and client dissatisfaction. Not our fault, but a reality. The client will be disgruntled with my company when endless issues arise doe to our works, every time I come in to do some work. 

Inconvenience is not a defence - I know. 

3) Safe working in this environment takes some training and most importantly developing of safe working habits. - eg: always work as if its live,  watch out for the loose cable ends and flicking back onto a live screw on the MCBs, tighten all connections before any cable manipulation, be very careful of the hole saw and its direct effects, including the burning hot hole saw waste dropping onto existing cabling, do, and make safe, all the dead part of the job before you access the live part of the job, the list goes on and on.

Some hypocrisy here by me,  but this what I should probably do better than I do now too - put together a tool box talk and get the guys to sign it, sign the RAMs, and go a little overboard in issuing safety gear, and get them to sign for that lot too. I've done all of this periodically in the past but probably should do again.

Of course like everyone else, I think - I'm as safe as can be in this environment and I am happy days working on a live DB,  but as the QS and you're responsible for others working practices and methods, it gets a lot more difficult hey? 

As for 1 vs 2 guys........I can't offer formal guidance, just my musings.........

I'd suggest 2 is better than one, but if that 2nd man is only there for kicking the first man, then for financial reasons, he doesn't need to be so experienced, perhaps an apprentice. He/She will land up with their sticky fingers in that DB too, so good supervision and real life training needs to come from the electrician next to them, supervising. Perhaps a supervising training course is order.....it does get a little endlessly difficult doesn't it?

In my recent SMSTS refresher, we did cover a section on lone working, while not necessarily electrical related, perhaps see what the GE700 document used on that course has to say?

Is your 4 county work for the council and do they have their own demands?

This is just my personal opinion.

On or Near a 3 phase LIVE board.  Yes 2 person job for safety reasons.

Now the real question

Why do they need to work LIVE?

Daniel S Robinson said:

So my question is, if the electrician is carrying out dead tests on the worked on circuit that is housed in a DB that can't be isolated, should two people be present.

Why can it not be isolated?

Amazing guys thank you for your input. I'm due to discuss it with the four other QS's in the business next Monday. I really think if its a communal area and the board just houses sockets and lights there is no reason not to turn it off. If on the other hand it has the fire alarm, warden control systems and help lines I think we will put a process in place whereby we can work on the live board depending on its age and other factors. I will feed back what is decided. Just good to get other peoples thoughts. We are a housing association by the way with around 65 operatives so its important to get this right.

The other question that comes to mind is whether DBs should be a special case - most of the hazards are also potentially present elsewhere - e.g. in single phase DBs or other 3-phase equipment or just re-connecting tails to henley blocks. Is there a more general live working policy to be considered?

   - Andy.

The five levels of control to eliminate or reduce risks, in order of effectiveness, are:

    Elimination
    Substitution
    Engineering controls
    Administrative controls
    Personal protective equipment (PPE)

Remember the safety triangle.

The following 2 web sites could help with the safety/business case discussion/debate

https://www.hse.gov.uk/ppe/managing-risk-using-ppe.htm

https://www.tsw.co.uk/blog/health-and-safety/hierarchy-of-control/

Only work live when it is essential to do so.

If you must, ensure that the correct PPE is worn. (Rather like DNOs jointing live.)

I am not sure that having a second person present helps. How does the second help the first who has just had a shock? Does he or she carry a defibrillator? Could both be killed or injured?

I am not sure that the number of phases matters - it is still 230 V to earth.

Daniel S Robinson said:

If on the other hand it has the fire alarm, warden control systems and help lines I think we will put a process in place whereby we can work on the live board depending on its age and other factors.

There’s something seriously wrong if those safety services will not work during a power cut.

The second person could isolate the power upstream, administer first aid and call an ambulance.

I don't suppose many organisations' health & safety policies would allow employees to do dangerous work alone.