What cable size to run to the garage.

[Dave-sparks]

Last time I bought some SWA cable the price for the correct coloured stuff was crazy,

If by 'correct' you mean SWA with brown, blue and green/yellow cores then that is non-standard cable.

Standard 3 core SWA is brown,black,grey (3 phase and earth, the armour being the earth)

 

[RaceDiagnostics]

Is this a TN-S connection?

 

[Morrisman]

If by 'correct' you mean SWA with brown, blue and green/yellow cores then that is non-standard cable.

Standard 3 core SWA is brown,black,grey (3 phase and earth, the armour being the earth)

Lord knows, but I priced up the stuff I was told I had to use on a garage building web site several years ago, and a local electrical shop told me a far cheaper alternative.

 

[RaceDiagnostics]

Just something to note.

Depending on the construction of the garage and the earthing arrangement, two core may not be suitable.
Chances are you are on a PME supply, and when exporting the earth you need to consider bonding - the armour of the cable may not be sufficent.

If you want to be sure and cover yourself, install a three core.

It's a brick garage with no gas/water or extraneous metal parts, I don't think the metal up and over door counts as extraneous. So would I need to consider a thicker earth for bonding?

I think I have TN-S supply (old house), not a TN-C-S with PME.

 

[brightspark]

I would pay the extra and go for three core.

Bob

i would use 3 core depending on the earth arrangements at the supply.if its a tt incomer id only use 2 core and the garage tt with earth rod if the board supply the earth id use 3 core one as the earth and just bond the steel braiding

 

[Barking Mat]

You're running underground compressed air pipes?

That's the plan.

 

[jimbo84]

It's a brick garage with no gas/water or extraneous metal parts, I don't think the metal up and over door counts as extraneous. So would I need to consider a thicker earth for bonding?

I think I have TN-S supply (old house), not a TN-C-S with PME.

View attachment 447992

I’d say a TN-C-S but looks like an old PILC so depends what’s going on in that service head and whether or not there is a link in it. You can enquire to the DNO and they should be able to tell you but it all depends on how up to date their records are.

The TN-S thing is a bit of a moot point now anyway and some schools of thought recommend TN-S supplies should all be considered to be TN-C-S due to the fact that any repairs that have previously been carried out underground will convert it to a TN-C-S supply by the way the DNO now repairs cables.

If there’s nothing extraneous in the garage there’s no need to run a 10mm bond back to the house but a 10mm 3 core cable or above would cover you for that anyway.

There are some schools of thought that you shouldn’t export the PME earth regardless and all outbuildings should be TT’d with a rod but that is a whole other can of worms that no-one can definitively agree on.

 

[Guineafowl]

 

[aesmith]

You want to buy the swa especially for car chargers with the inbuilt data cable for the CT clamp meter thing.

That only helps if you run that special SWA all the way from the meter location direct to the charger. In reality his charger would more likely be fed off a sub DB in the garage.

 

[addjunkie]

That only helps if you run that special SWA all the way from the meter location direct to the charger. In reality his charger would more likely be fed off a sub DB in the garage.

Chargers need a ct clamp at the meter to allow them to regulate if the house hold demand when charging is excessive.

 

[RaceDiagnostics]

I plan to put a conduit in at the same time (plus a bit of string) so I can add data cables later if necessary. No point in putting in expensive SWA with the twisted pairs as it won't go all the way to the charger anyway, as described above it will only go to a CU in the garage.

 

[sparkysy]

I plan to put a conduit in at the same time (plus a bit of string) so I can add data cables later if necessary. No point in putting in expensive SWA with the twisted pairs as it won't go all the way to the charger anyway, as described above it will only go to a CU in the garage.

Ah yes but it would be most of the way and can be gel crimped and extended to the charger.
Personally i would go one size bigger than what i calculate, future proof the project.

I would just use standard 3core swa in a duct for future additions.
The amount of times I have had to have extra trenches dug after completing a job is ridiculous!
Sy

 

[aesmith]

Chargers need a ct clamp at the meter to allow them to regulate if the house hold demand when charging is excessive.

Yes of course I understand that. My point is that this recommended SWA with twisted pair included is not much help unless it runs right to the meter location, unlike for example ours which splits off some way away from the meter. And unless it runs all the way to the car charger, ie dedicated for that sole purpose, rather than feeding a DB in the garage.

 

[Erie Fred]

I would use 4" conduit, and while I have the trench open, make (2) runs of it.
Either side by side, or a skinny trench, on top of each other.

 

[aesmith]

I'd probably bury the SWA, going oversize to play safe, as I think it ould be a right pain drawing in 25sq.mm cable even in a big duct. Then run one or two 40mm or bigger ducts for the future. Bear in mind you're not supposed to run network or signal cables in the same duct as power.

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