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

 

[SimpleSimon]

Your main switch at your consumer unit which is double poles will satisfy this point.

 

[claire_r]

Basically when working on tt turn the lot off!

 

[simonspark]

No. It doesnt say that. Thats what I always thought. Ok, I'm gonna type out the whole bloody thing.
ii Other than at the origin of the installation, every circuit or groups of circuits that may have to be isolated without interrupting the supply to other circuits should be provided with it's own isolating device. This device must switch all live conductors in a TT system and all line conductors in a TN system.

See what I mean?

 

[Risteard]

every circuit or groups of circuits that may have to be isolated without interrupting the supply to other circuits should be provided with it's own isolating device.

Do any circuits need to have the facility to isolate without isolating other circuits though?

 

[telectrix]

Do any circuits need to have the facility to isolate without isolating other circuits though?

that's what your MCBs are for, as well as OCP.

 

[Risteard]

that's what your MCBs are for, as well as OCP.

Not in a TT system - a single-pole device is not suitable for isolation. Hence the main switch.

 

[Knobhead]

Am I missing something here? Line and live? Has someone redefined neutral as live?

 

[Risteard]

Am I missing something here? Line and live? Has someone redefined neutral as live?

Neutral has always been live.

 

[simonspark]

Risteard. Sorry mate but Ive already typed this once before and I don't know where it went! But as I tried to say (puff!) Yes. According to the wording of the paragraph. It also cross references Regulation 537.2.1.1. Whatever that may be