Changes to reg 411.3.3 PEN Conductor.

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lav89

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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

 
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

 
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

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