Domestic Installer - a scheme that covers general electrical installation work in UK domestic properties only

As an electrician that mainly does domestic work  I only see 3 phase maybe once or twice a year. Then on most occasions it has fairly limited impact on what I do, 

Personally I think I have had enough training and knowledge to perform the work safely. But as I don't do it often I recognise that I have to step back and think about things more carefully. But that's like most things in electrical work, there are so many different aspects to the job that many of us will come up against things we haven't done before or in a long time on a regular basis and have to so some back ground work.

I would say the one downside of bs7671 used on its own is that its not a good solution for identifying potential risks to think about. Its great for finding answers when you know what the question is.

We have these crazy long check lists for an ev instal, maybe a list of things to think about with 3 phase would be useful.

Phase rotation, phase balancing, make sure protective devices are compatible with a 3 phase board,make sure you buy boards that allow instalation  of an spd if required make sure adjacent sockets are on the same phase, how are you going to achieve a switched neutral if required, do single phase bidirectional rcbos for a 3 phase board exist or would you need a seperate board etc.

Overall I think the hard part is working out how to comply with regs in a 3 phase environment, compared to single phase  things we do day to day suddenly change slightly and become more complex.

I found a good example recently. Electrician had clearly forgot about buying boards that supported spds. They have bolted some spds inside the board. Totally invisible outside  have to move wires inside to see them. Customer won't be able to see if they failed and its going to take hours to change a module.

adjacent sockets are on the same phase

Why? That requirement disappeared decades ago...

   - Andy.

AJJewsbury said:

That requirement disappeared decades ago...

For very good reason ... although in domestic situations I'd still recommend arranging things so that, as far as possible, simultaneously-accessible socket-outlets are on the same circuit.

"as far as possible, simultaneously-accessible socket-outlets are on the same circuit"

 I must say I am not entirely clear why you would really need to worry much about that. The idea that the whole circuit means it all goes off all at once is actually something of a pain if the ADS ever operates, as indeed it is in countries where lights and power are on shared 16A circuits. 
That said, when I was working in Germany in the early 2000s common domestic practice was that lights and power shared, and it was one floor per phase for all the single phase stuff, at least for houses with 2 floors and a cellar, and cellar and attic shared a phase if there were both.

We are now a longish lifetime away from the old AC/DC radios and TVs that had the metal chassis attached to one pole of the mains, and 2 pin plugs that meant that half the time, that pole was a live phase. Nothing that meets modern product standards is made that way, so the only time you would be holding something live is under fault conditions. Given the whole ADS strategy hinges on simultaneous independent faults being improbable, we should afford the two faulty appliances side by side the same likelihood.

regards Mike

"as far as possible, simultaneously-accessible socket-outlets are on the same circuit"

 I must say I am not entirely clear why you would really need to worry much about that. The idea that the whole circuit means it all goes off all at once is actually something of a pain if the ADS ever operates, as indeed it is in countries where lights and power are on shared 16A circuits. 
That said, when I was working in Germany in the early 2000s common domestic practice was that lights and power shared, and it was one floor per phase for all the single phase stuff, at least for houses with 2 floors and a cellar, and cellar and attic shared a phase if there were both.

We are now a longish lifetime away from the old AC/DC radios and TVs that had the metal chassis attached to one pole of the mains, and 2 pin plugs that meant that half the time, that pole was a live phase. Nothing that meets modern product standards is made that way, so the only time you would be holding something live is under fault conditions. Given the whole ADS strategy hinges on simultaneous independent faults being improbable, we should afford the two faulty appliances side by side the same likelihood.

regards Mike

mapj1 said:

I must say I am not entirely clear why you would really need to worry much about that.

In a place of work, agreed, no worries ... accessing a live conductor is a breach of legislation.

In domestic premises, access to live terminals by the curious is possible, as we have seen numerous times, by defeating shutters and poking things into the socket-outlet. Yes, this is mis-use ... but not necessarily a breach of legislation if a private individual does this in their own home (it could be considered negligent ... or a breach of a duty of care ... but that's a different matter).

If we consider, however, someone accidentally bridging both live conductors with themselves, if the RCD protecting the circuit is not bidirectional, there is no guaranteeing the RCD protection will operate ...

All mis-use, granted ... but the same went for the former consideration of having socket-outlets on the same phase if they are simultaneously accessible ...