TN-C-S / Pyro / Outbuilding Upgrade

[SW1970]

Hi, bit of a job with scope creep going on. "Oooo it's so good we've found a nice electrician we can get all these things done that we've wanted for years". Client wants new outside lights on garage but existing isolation and circuit protection supplying garage is falling apart so that needs sorting too. Circuit to garage is on buried 2 core pyro of unknown depth and routing. Existing old Wylex isolator and fuse in meter cupboard is rusting and existing old Wylex isolator and fuses for lights and sockets has no RCD (sockets are used for outdoor equip). So these items need replacing and upgrading. Primary concern is earthing, installation is TN-C-S. Earthing to MET is ok. Have a look at this sketch (red is new equipment replacing old, blue is existing and propose to retain):



First time I've worked with pyro. Not sure which rating as existing terminations aren't marked so assuming worst case from Lenny's sticky it's 8.2mm2 equivalent. Any thoughts or guidance on this one? Many thanks as usual!

 

[Knobhead]

Look at past posts :cowboy:

 

[oxocube]

Pyro is not suitable for burying direct and it is an extraneous conductive part. I'd start from scratch and abandon all the existing.

Edit - where I have said its an extraneous conductive part is incorrect and is nonsense.

 

[SPARTYKUS]

Spade'd go straight through it

 

[Knobhead]

Spade'd go straight through it

As an apprentice I put a piece of pyro across an anvil with a 1000V Megger connected. It took about 5 belts with a 14lb sledgehammer to break the insulation down!
It’s as tough as old boots!

 

[SPARTYKUS]

If you'd used a spade it'd have gone straight through it.

 

[mattmoo1974]

Spades have been known to go throught SWA as well, Pyro is a good cable and still insisted on in some locations, problem is, like always, more and more so called electricians have never used it, or know how to pot and terminate it.

Iv got pot and no how to use it!

 

[SPARTYKUS]

Spades have been known to go throught SWA as well, Pyro is a good cable and still insisted on in some locations, problem is, like always, more and more so called electricians have never used it, or know how to pot and terminate it.

Too true. Would last longer though!

 

[Deleted member 9648]

Pyro is not suitable for burying direct and it is an extraneous conductive part. I'd start from scratch and abandon all the existing.

The pyro is not an extraneous conductive part,it is a conductive part as it is the supply cable to the garage and part of the electrical installation.
Whilst I agree that a direct buried pyro is not ideal,as it is already there,and if it tests out ok and is of adequate current carrying capacity I cant see the point in changing it.....use it.

 

[SPARTYKUS]

Hardly !!!!Try a light sabre :single ****:

You haven't seen my spade

 

[oxocube]

The pyro is not an extraneous conductive part,it is a conductive part as it is the supply cable to the garage and part of the electrical installation.
Whilst I agree that a direct buried pyro is not ideal,as it is already there,and if it tests out ok and is of adequate current carrying capacity I cant see the point in changing it.....use it.

So you inventing a new reg, buried metalwork is no longer an extraneous conductive part, lol.

 

[SPARTYKUS]

Sw1970, apologies if Ive wandered with my lethal diamond tipped spade on your thread. I hope you can come to a satisfactory conclusion as to what to do!Wirepuller-would you want to see / confirm its depth over the run?

 

[Risteard]

So you inventing a new reg, buried metalwork is no longer an extraneous conductive part, lol.

It is an EXPOSED conductive part. That is why the sheath is earthed, not bonded. It is also used as the cpc.

 

[Deleted member 9648]

So you inventing a new reg, buried metalwork is no longer an extraneous conductive part, lol.

An extraneous conductive part cannot be part of the electrical installation....I am not inventing regs...you will find this information in the definition of an extraneous conductive part in the BRB/BGB if you bother to read it.......(lol)

 

[Deleted member 9648]

Sw1970, apologies if Ive wandered with my lethal diamond tipped spade on your thread. I hope you can come to a satisfactory conclusion as to what to do!Wirepuller-would you want to see / confirm its depth over the run?[/QUOTE]

As long as there were no obvious issues...no I wouldnt. I would just do a cert to cover work within the garage,as the refurb of the garage install and a few additional points is the object of the excercise.

 

[Deleted member 9648]

They are still both earth though are they not so can we put the toys back in the prams please !!!

Not when I am told I dont know what I'm talking about by someone who doesn't know what he's talking about.

 

[ayjay]

bet noone knows what heatshrink was---it came out about 25 years back but was discontinued it replaced the micc pots , had to use a special attachment on a blowlamp to terminate it
also there were pots that didnt screw on, they had a separate brass wedge instead-- and you had to use a converted set of molegrips to crimp the wedge into the pot
micc is very underrated imo this new stuff is impregnated with silicone so it doesn,t get moisture in the insu, not like the old days, no silicone then-- u had to work fast or the meggar reading would be low
if an old mineral had damp in it you used a blowlamp to drive it out after removing the pot
bloody sparks these days wouldn,t know **** from clay, if they were presented with an micc job

 

[Risteard]

Mineral Insulated Copper Clad, also known as MIMS (Mineral Insulated Metal Sheathed) or Pyro.

 

[malcolmsanford]

]Pyro is not suitable for burying direct[/B] and it is an extraneous conductive part. I'd start from scratch and abandon all the existing.

I have to ask why not

 

[Deleted member 26818]

So you inventing a new reg, buried metalwork is no longer an extraneous conductive part, lol.

Metalwork such as water, gas or oil pipes or steel reinforcing in concrete are extraneous-conductive-parts.
Mettalic cable sheaths, conduit or trunking and metal enclosures are exposed-conductive-parts.