Commercial periodic question

[Phil Mumford]

Commercial periodic with loads of IT kit. One or two of the disboards have 4 pole isolators/main switches. I believe switching the neutral in some cases is incorrect and potentially dangerous.

When should you NOT switch the neutral conductor??

Thanks in advance for any info.

 

[glenneth256]

Hi There,

BS7671:2008 regulation 537.2.1.1 states that "Every circuit shall be capable of being isolated from each of the live supply conductors. In a TN-s or a TN-C-S system, it is not necessary to isolate or switch the neutral conductor where it is regarded as being reliably connected to Earth by a suitably low impedance."

I have never come across a situation where disconnecting the neutral is dangerous. In fact it's a bonus if you can, less risk of picking up a back feed through the neutral conductor for total isolation. Although according to the reg's not essential.

Cheers

Glenn

 

[Phil Mumford]

Thanks for the info/advice.

 

[Amp David]

You thinking of a fused neutral?

 

[Phil Mumford]

Not a fused neutral - this is 4 pole incomers on the 3 phase disboards. My inspecting engineer thinks there may be a problem with switching a neutral/PEN conductor in this scenario.

I don't see a problem - hence the post !

 

[electricAl]

Don`t see a problem either.

If 537.2.1.1 does state that (unable to check at this mo) then as the Neutral is now considered a LIVE conductor...

Hope it helps

 

[Amp David]

Not a fused neutral - this is 4 pole incomers on the 3 phase disboards. My inspecting engineer thinks there may be a problem with switching a neutral/PEN conductor in this scenario.

I don't see a problem - hence the post !

Ah OK.