Main Switch/isolator

[Phaze-3]

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.

 

[Guest111]

main switch to isolate,otherwise how do you carry out maintenance.

 

[Engineer54]

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!!!

 

[Phaze-3]

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

 

[Engineer54]

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!!

 

[Knobhead]

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.

 

[Phaze-3]

Would you guys say it is 'POTENTIALLY DANGEROUS' by not having one installed?

 

[Silly Sausage]

If I dare quote a BS7671 regulation, have a look at 537.1.4 (and 537 in general)

If you're doing an Inspection, C3 and quote above reg.

 

[Phaze-3]

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.

 

[Phaze-3]

Rang the NIC EIC and they deem it to be a C2.

 

[Silly Sausage]

Rang the NIC EIC and they deem it to be a C2.

Yeah, but they write their own regulations!
Did they explain where the potential danger was?

 

[sparkymalarky]

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.

 

[Engineer54]

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!!

 

[KAS1]

Does the said bus bar chamber belong to the distributor or to the electrical installation?

 

[SirKit Breaker]

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