Only Live conductors in a metal enclosure

[anything electrical]

Hi
I am installing a Teletask Micros+ Home Automation metal enclosure
Is it ok to bring just Live and SW Live conductors though a 400mm by 20mm slot cut in the rear of the enclosure ( sometimes cut in the base )
I know I have to bring L N CPC conductors through the same hole but the N and the CPC conductors are all terminated in the large plastic trunking which is mounted underneath the panel to keep it neat & because there is not enough room in the metal panel for them all

Thank you

Paul

 

[John D v2.0]

You don't need neutral but you need to earth the enclosure with the cpc anyway so you'll have to bring it in for practical reasons as well as regs reasons
Also if it's metal make sure you protect the cables with grommets or something as the edges will probably be sharp.

 

[endecotp]

Is it ok to bring just Live and SW Live conductors though a 400mm by 20mm slot cut in the rear of the enclosure ( sometimes cut in the base )

If you're referring to the need to avoid unintentionally creating a transformer, then the answer is yes.
If a metal enclosure only has one opening in use then there can never be a problem (topology).
There may be other reasons why you need more wires, e.g. the earth as mentioned above.

 

[Taylortwocities]

Hmm. Just had a thought. As Earth and neutral are at the same potential, could there also be issues with eddy currents etc if the line and the earth come through separate holes in the metal enclosure?

 

[anything electrical]

thank you for the quick replies

the panel has a 3 core mains flex which powers the power supply which earths the panel & an internal earth bonding point

I was worried about regs ( 521.5.1 Ferromagnetic enclosures: electromagnetic effects )

this is the panel https://www.teletask.be/media/2454/tds10012_en.pdf

Thank you

Paul

 

[Adam_151]

Hmm. Just had a thought. As Earth and neutral are at the same potential, could there also be issues with eddy currents etc if the line and the earth come through separate holes in the metal enclosure?

I'm not quite sure on the logic there "As Earth and neutral are at the same potential", but to answer the question the best I can, as the earth isn't carrying any current normally under normal conditions there won't be any effect. Under fault conditions, there will be some magnetic losses, which will manifest themselves in the reactive component of the earth loop imepedance. In domestic, neither is likely to be a problem, on big stuff the extra impedance in the fault loop might be an issue and the losses into the enclosure could possibly cause undiresable thermal or physical effects, I would imagine

 

[Adam_151]

I was worried about regs ( 521.5.1 Ferromagnetic enclosures: electromagnetic effects )
Paul

I think you are picturing it wrongly when you say you have to bring L and N through the same hole. What we really mean is that the sum of the currents through the hole must always be zero. So yes you can bring a conductor in through a hole, switch it and take it back out through the same hole. You would have for example X amps on the feed, and minius X amps on the switch wire (the current in the two wires is opposite to each other). If you were to instead get confused and after taking your feed into the enclosure, then take your switch wire from the outside in again, like some weird kind of stitch, then not only would you not be able to put the lid on!, the current would be running in the same direction as the first and you'd have 2X. If you have a clamp meter you can prove this...

 

[bernardgreen]

 

[John D v2.0]

Yes as said it's the current through the holes that matters not the potential of the conductors going through.