Changes to reg 411.3.3 PEN Conductor.

[lav89]

Hi, this is my first post, and I hope it doesn't come across as a stupid one.

I am a qualified spark who primarily works on subsea equipment on vessels, thus the 17th and 18th edition regs are not really required for what I do.

However, I do always keep myself updated with the current regs for when I do work at home. 

My question, I have read one of the changes is regulation 411.4.3 has been modified to include that no switching or isolating device shall be inserted in a PEN conductor.

My understanding was that on said systems, if for example you were moving a fuseboard and the tails were to be over 3metres long you would install a switched fuse unit to protect the cables, how are we now supposed to protect said cable without installing such devices. I do understand the logic of it though ( I THINK!) , the concern is that should the device that's protecting the meter tails become faulty and somehow manage to lose the PME to the fuseboard you would then have a broken PME and be in trouble.  Also then, what about the double pole isolators that the DNOs fit , does this class as an isolator on the PEN conductor?

I hope I have read it right and don't look a complete donkey haha! Its just one of the changes that stood out to me when ive just read them.

Thanks

 

[ProDave]

But all this happens AFTER the meter where N and E are separate.

 

[Andy™]

in most installations, the earth is seperated from the neutral at or before the service head, before 7671 applies. your neutral is just a neutral

 

[Evans Electric]

Its not a daft question  . 

Definition of a PEN  conductor .        ( I may be wrong  so don't alter your Regs book to  " Well Deke said ....)  

A conductor combining the functions of  BOTH   earth & Neutral  conductor . 

I've worked on only a couple of jobs  that are now called PEN  conductors ,    we called it concentric wiring .     You can't actually do a job like it without Home Office permission  I was told .    

A typical  PEN  job  ( as I see it , someone knowledgable  will correct us )          was  1 core concentric pyro   , centre core was  L  ,  the sheath was E & N   (or PEN)   I presume.

The pyro pot had a long tail on it ........ you made the pot (no gland)  off into a clamp box ..... without cutting the tail you sleeved the first bit  green  connect to back of box . Sleeve the next bit  black  connect to N   ..... sleeve the next bit green looped into the E terminal   .  1

 

[Tony S]

That is similar to SWER (single wire, earth return) used for MV distribution in some countries. Thank god it’s not allowed here.

 

[kerching]

@Evans Electric

that CAD upgrade was worth the money!

 

[Evans Electric]

You mean mine  of course  ?/  Not Tony's ?  His is just rubbish !!