Supply to garage.

[Edward67]

Hi ok here we go.
Friend has asked if can rewire his garage as he is turning it into a gym. I said ok no problem.

He the put the spanner in. Ok I want
1 circuit for a car charger. 7.4kw.
2 x 3kw heaters
1 x ring main for gym equipment. From what i can tell running machine is most power hungry.
1 x lighting circuit.

All on a 2.5mm incoming swa.

So now I need to split the meter tails.in the cupboard and put in 25mm swa cable. Run about 12 meters.

Pme 80amp.

So looking for thoughts.

He needs cutout upgrading to 100amp. Its large 5 bed already with a hot tub.

Do you think I should install 2 core swa and TT the garage.

Or 3 core swa to mini board in meter cupboard then to isolator.
Or a two core swa with separate earth cable run next to it. This is better as earth can be smaller diameter.

Due to the size of the earthing conductor with the mini boards even accept them.

Or thinking outside the box. I could run the swa and terminate to a metal bracket mounted in the meter cupboard then run into a double isolator switch which will protect the current house tails and new swa tails.
The issue with this is the tails from the bracket to isolator are not double insulated.
However they are In cupboard that requires a key to enter so does that comply. I'm not sure.

I already know about the debated exporting pme conversation so don't wish to revisit it please.

Looking for ideas or pictures of people who have performed this.
If it wasn't for a friend I would refuse because sometimes it's best to DGI.

All comments appreciated.

Pic.of meter cupboard attached. Mmmm loads of space? think there is room for mini board.

 

[davesparks]

I was referring to an article in electri

Exporting A PME Supply To Another Building

In this article the technical team at Stroma Certification offers expert guidance on exporting a PME supply to another building. One of the most common queries to the Stroma help desk concerns running

professional-electrician.com

Doesn't say it's not allowed but was referring back to this.

Ah yes, that well known source of verified technical information, the freebie mag from the wholesalers.

The article makes some good points but also makes some mistakes.
There is nothing, as far as I am aware, preventing the use of an earth from a PME supply being used in a building with a concrete floor.
I'm sure a lot of us have been to, and worked on, installations which have a PME supply and a concrete floor.

 

[radiohead]

I'm sure a lot of us have been to, and worked on, installations which have a PME supply and a concrete floor.

Probably a majority of buildings with a PME supply have a concrete floor.
My house does. And so does my attached garage, it's on the same PME as the house.
I do often wonder why the 'exporting' thing only seems to apply to PME??
Why dont we 'export' TT or TNS?
And why does it only apply to outbuildings? Why does the fear of PME seem only to apply to outbuildings?
I 'exported' the PME to a socket by a pond last week, never ever seen anyone TT a pond socket..

 

[davesparks]

I 'exported' the PME to a socket by a pond last week, never ever seen anyone TT a pond socket..

I'd keep quiet about that if I were you, otherwise someone will be along with an eath rod and drive it straight through your pond lining!

All that water leaking down the earth rod will be great for keeping the Ra down, but pretty terminal for the prize koi!

 

[TJ Anderson]

Probably a majority of buildings with a PME supply have a concrete floor.
My house does. And so does my attached garage, it's on the same PME as the house.
I do often wonder why the 'exporting' thing only seems to apply to PME??
Why dont we 'export' TT or TNS?
And why does it only apply to outbuildings? Why does the fear of PME seem only to apply to outbuildings?
I 'exported' the PME to a socket by a pond last week, never ever seen anyone TT a pond socket..

It only applies to PME because of the of the potential risk of exposed and extraneous conductive parts rising to mains potential if the PEN conductor suffered a broken earthed neutral and the line conductor stayed intact. This cannot occur on a TN-S or a TT as they have separate conductors.

 

[radiohead]

It only applies to PME because of the of the potential risk of exposed and extraneous conductive parts rising to mains potential if the PEN conductor suffered a broken earthed neutral and the line conductor stayed intact. This cannot occur on a TN-S or a TT as they have separate conductors.

I understand the potential dangers of PME supplies, I don't need that explaining.
But it does not explain why only PME is apparently 'exported', TNS and TT are also 'exported' where they feed a remote installation .
Neither does it explain why PME is only ever 'exported' to outbuildings. There are many other situations remote from the intake where 'exported' PME is never questioned. The pond socket I installed last week. External lighting/garden lighting. I recall a job a few years back where the installer had fed a string of drive light columns from the TNCS house supply, and run a distribution circuit to a summer house which had been separated and TT'd......so they couldn't export the PME to the shed but it was fine on the drive lights!
I just hate the term 'exported' and the lack of logic behind only applying it to outbuildings.

 

[TJ Anderson]

They only mean extending the earth outsider by the term exporting so I am not worried about the terminology. They could be more specific regarding outbuildings (as with Caravans) but it is really because the impact of a PEN failure is likely to be more severe with some outbuildings dependant on what is being supplied in them. Lots of class 1 metal cased equipment for example and also just having exposed ground or concrete. Also what is the likelyhood of someone being in contact with it. The way it is at the moment allows an electrician to apply his/her judgement and I prefer that.

My home has PME. My garage is remote from my house and I utilise the distribution circuit earth. I don’t have lots of metal cased class 1 equipment. If I did, I might consider changing it to TT.

Your pond pump (likely class 2) would not be any risk at all even under an PEN failure conditions.