OSG. Page 33. Is this right?

[simonspark]

Hello all.
The other day I was leafing through the red OSG and for no reason started to read chapter 5, isolation and switching. At point ii for every other circuit it says blah blah blah......... The device must switch all live conductors in a TT system and all line conductors in a TN system.
The latter point I have no problem with. It's the former. Does this mean ( you should read the full paragraph to be honest. I couldn't be bothered to type it!) that in a TT system all circuit breakers should be double pole? It certainly reads that way in my eyes.
I rarely have any dealings with TT systems, so I don't get involved. But one day I may need to know the answer to this. Anyone?
Simon

 

[scotsparky]

Well not got the BRB to hand so had a look at my Shinney BGB and in that it Reg 537.2.1.1
says Every circuit shall be capable of being isolated from each of the live supply conductors . Ina a TN-S or TN-C-S system the it is not necissary to isolate or switch the neutral conductor where it is deemed to have a reliably connection to earth by a suitably low impedance

Provision may be made for isolation of a group of circuits by common means.



What i take from that is on TN systems you can islolate phase conductors only but TT its Phase neutral and 1 switch can cover all.

 

[vernam616]

Would explain why the porter cabins that i wire a temporary supply up to, all have double pole mcb's installed in the internal D/Bs

 

[simonspark]

Double pole mcb's are brilliant. Hager makes a board that uses a twin bus bar. One live, one neutral. These are offset so that you just drop the dp mcb (or rcbo or cartridge type fuse holder) onto the twin bars.The dp breakers take up the same space as a single pole one. No neutral bar required. No more huffing and puffing trying to work out which neutral goes with which phase when testing.
All boards should be made this way. And, except in certain circumstances, mcb's should be done away with and every final circuit should be protected with rcbo's.

 

[Knobhead]

Double pole mcb's are brilliant. Hager makes a board that uses a twin bus bar. One live, one neutral. These are offset so that you just drop the dp mcb (or rcbo or cartridge type fuse holder) onto the twin bars.The dp breakers take up the same space as a single pole one. No neutral bar required. No more huffing and puffing trying to work out which neutral goes with which phase when testing.
All boards should be made this way. And, except in certain circumstances, mcb's should be done away with and every final circuit should be protected with rcbo's.

I wondered how long it would take the £SD brigade to jump on the bandwagon!

 

[simonspark]

Whats a £SD

 

[telectrix]

used to be a little white pill

 

[telectrix]

Double pole mcb's are brilliant. Hager makes a board that uses a twin bus bar. One live, one neutral. These are offset so that you just drop the dp mcb (or rcbo or cartridge type fuse holder) onto the twin bars.The dp breakers take up the same space as a single pole one. No neutral bar required. No more huffing and puffing trying to work out which neutral goes with which phase when testing.
All boards should be made this way. And, except in certain circumstances, mcb's should be done away with and every final circuit should be protected with rcbo's.

if only carlsberg made CUs.

 

[JUD]

Hi Tony,

I believe the regs book does say somewhere that the neutral conductor is treated as if it was a live conductor.

Best wishes

Rex

It's in the definitions....

Live conductor (see Live part).

Live part A conductor or conductive part intended to be energised in normal use, including a neutral conductor but, by convention, not a PEN conductor.