Discuss Main Switch/isolator in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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Hi Guys,

Right, 3 phase supply into main distributors fuses, then through the meter then feeding a busbar section. The from the busbar section is feeding 3 main isolators feeding dis boards.

Does there need to be a main switch or isolator between the meter and busbar section? Or is the distributors fuse good enough for isolation (even if you have to get the distributors in to isolate them.
 
Hi Guys,

Right, 3 phase supply into main distributors fuses, then through the meter then feeding a busbar section. The from the busbar section is feeding 3 main isolators feeding dis boards.

Does there need to be a main switch or isolator between the meter and busbar section? Or is the distributors fuse good enough for isolation (even if you have to get the distributors in to isolate them.

In a word, ALWAYS!!!
 
But is it a nice to have or is it against the regs.

If you was to do a ECIR on this installation would you list it down as a deviation it not having 1 and if so what code would you put on it. Personally I would say a C3.

What do you guys think
 
Frankly, i wouldn't and don't care what is says in BS7671, You would never have a Bus Bar chamber connected direct on to the tails of a supply without a form of isolation. A straight isolator wouldn't be my first choice either, but better than nothing at all!!
 
Frankly, i wouldn't and don't care what is says in BS7671, You would never have a Bus Bar chamber connected direct on to the tails of a supply without a form of isolation. A straight isolator wouldn't be my first choice either, but better than nothing at all!!

E54 I never thought I’d hear you say that and I fully agree.
Unfortunately BS7671 wasn’t written with good engineering practice in mind. A fused switch would be my choice in this situation.
 
Thanks Archy,

This was the route I am thinking of taking. Even though BS7671 states it, its not a C1 or C2 as its not in anyway dangerous.
 
It is against BS7671 NOT to have one.

As said before Reg.No.537.1.4 and if you want to be reall pedantic about it Reg.No.132.15.1

If a main switch is missing, its a C3 in my book. There's no danger at present, or is there the potential to be danger providing everything else is in order. Engineers site-based decision.
 
Would you guys say it is 'POTENTIALLY DANGEROUS' by not having one installed?


Of course it's potentually dangerous!! You can't isolate the bus bar chamber without pulling the main service fuses, which encourages unnessesary live working. Now think about the fault current available within that bus bar chamber which could easily be a 400A TP+N set-up?? As Tony has stated, a suitably rated Switch fuse or MCCB/ACB would be the ideal, ...but a straight isolator would be the very least i'd expect to see!! And if that requirement isn't stated in BS7671, then more shame on them!!
 
In my opinion, it comes down to whether or not it was or wasn't a requirement at the time the installation was designed, constructed etc. It may have been OK in days gone by, which means that it is still OK now, but i would give it a C3 just from using common sense, and to quote the honourable member Engineer54 "I dont care what the regs say either".

Cheers............Howard
 
In my opinion, it comes down to whether or not it was or wasn't a requirement at the time the installation was designed, constructed etc. It may have been OK in days gone by, which means that it is still OK now, but i would give it a C3 just from using common sense, and to quote the honourable member Engineer54 "I dont care what the regs say either".

Cheers............Howard

As far as my experience goes, i've never seen a bus-bar chamber of any size connected directly to meter tails, not in the 40 odd years i've been in the industry!!

I'd also argue the point with anyone that is stupid enough to say ''there is nothing wrong'' with such an installation. You are literary handing over the control of such an installation to the DNO, it would also warrant DNO seals being fitted too!! lol!!
 
We're talking about a Periodic Inspection here, as specified by the IET in BS7671, following regulations given in BS7671, following guidelines given in GN3 (IET publication) and inserting the results into forms specified by the IET in BS7671.

By your own early admission not to acknowledge BS7671, I think you've excluded yourself from this discussion!
 
We're talking about a Periodic Inspection here, as specified by the IET in BS7671, following regulations given in BS7671, following guidelines given in GN3 (IET publication) and inserting the results into forms specified by the IET in BS7671.

By your own early admission not to acknowledge BS7671, I think you've excluded yourself from this discussion!

I would argue with any of my institute colleagues on this matter. I didn't say that i don't acknowledge BS 7671, but it's not the be all and end all, in many cases it's confusing and at worst contradictory!! The difference being, is that i don't need BS 7671 to tell me when something is right or wrong!!
 
Main Switch/isolator {filename} | ElectriciansForums.net
Originally Posted by KAS1 Main Switch/isolator {filename} | ElectriciansForums.net
Does the said bus bar chamber belong to the distributor or to the electrical installation?

It might as well be, they would be the only people that can officially isolate the bus bar chamber!! lol!!

 

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