PME on a farm?...........

[HappyHippyDad]

I am about to install 4 sockets in 4 separate stone enclosures, housed within a large stone outbuilding. They have stone floors and are completely weatherproofed. They may be having small animals in them, goats, sheep etc.

The existing set up is TN-C-S.

BS7671 doesn't go into much depth with regards earthing. 705.411.4 just says a TN-C system shall not be used. Does this mean just TN-C, or does it also mean TN-C-S? It's a little confusing as the title to this regulation is TN system.

Is the thinking that there may be some potential between the PME earth and actual earth and that this potential could become lethal to livestock? Is this more likely in muddy, wet, earth floored barns or is it just as relevant in my situation above (all stone).

The existing electrical system has been very well installed, which leads me to think this has been thought out, as it must have been installed whilst this regulation was in practise...... making me think perhaps it doesn't need a TT for some reason. Here is a picture of the supply...

 

[loz2754]

705.411.4 just says a TN-C system shall not be used. Does this mean just TN-C, or does it also mean TN-C-S?

The note, just below this reg, says "This does not preclude the use of TN-C-S."

 

[loz2754]

Thought that picture was familiar:

Installing a 3 phase rapid EV charger? - in - UK Electrical Forum

, Installing a 3 phase rapid EV charger?, UK Electrical Forum, ElectriciansForums.net Est.2006 | Free Electrical Advice Forum and page_number.

www.electriciansforums.net

 

[loz2754]

Just to add that TN-C is exceedingly rare, as the protective earth and the neutral are connected together throughout the system.

 

[Pretty Mouth]

There is note 2 to 705.415.2.1 to consider:

Unless a metal grid is laid in the floor, the use of a PME earthing facility as the means of earthing for the electrical installation is not recommended

 

[HappyHippyDad]

The note, just below this reg, says "This does not preclude the use of TN-C-S."

Just realised I was looking in the Big blue, not the Big brown.
So this suggests it may be ok to use PME.
However, they recommend at earth grid is laid.
So really, TN-C-S is not going to be used if all the ground work is already laid?

 

[HappyHippyDad]

Thought that picture was familiar:

Installing a 3 phase rapid EV charger? - in - UK Electrical Forum

, Installing a 3 phase rapid EV charger?, UK Electrical Forum, ElectriciansForums.net Est.2006 | Free Electrical Advice Forum and page_number.

www.electriciansforums.net

It is rather nice to look at though

I don't know what it is about it, but it makes me feel calm.

 

[davesparks]

It is rather nice to look at though

I don't know what it is about it, but it makes me feel calm.

It's a bit of a poor job, there's a lot of unsupported cables for starters.

With a bit of thought, and some containment it could have been a lot better.