Garage supply

[toffee]

OK this is probably something that has come up many times before, sorry if it has.

I have a garage + utility room with a cold water supply into it .

I will be pitting a 4 way DB in the garage feed fed via SWA, from a split load board usal things sockets and lights etc small load so i am not worried about loading, cable sizes/MCB sizes etc

My question is about the earthing arrangements for the garage.
The house has a TNC earth system.

As the garage is not connected to the house would this mean that the house is outside the equipotential zone of the house? ( The garage is about 5 meters away from the house)

Do I need to convert the earthing system in the garage to a TT type (I remember reading something about this awhile ago but can not remember in what context).

 

[ezzzekiel]

no you could fetch the meb into the garage thus extending the zone,( and main bond the water supply) this comes up often and is really more an issue with tncs, however there is no requirement within the BRB it tends more to be a Dno rule that a tt is required.


I am pretty sure this will turn into an issue once again

 

[sparkylad]

I think you mean TNCS dont you Toffee ?
You will require a 10mm Main Bonding conductor to the detached garage to maintain the equipotential zone. Or------you will need to isolate the cpc in the supply to the garage {at the garage end of the cable only ] and then convert to a TT system with a rod installation.

 

[toffee]

The all important 'S' looks like I did thanks. Cool so both ways are fine, think I will go with the TT system, less cabling and a neater job, (just the one cable to bring from the house to the garage).

 

[sparkylad]

Yep Toffee . but if you made the SWA 10mm 3-core then the cpc in it can also double up as the Main Bonding conductor.......just another option open to you

 

[wade88]

Hi guys,

Im about to embark on something very similar to Toffee for my elecsa assessment job. But being brand new to the game, can someone please just run over that again for me!

The garage i will be working on is also about 5 meters from the main house. So as far is earthing is concerned i must either convert to a TT (the house is currently TNC-S) or i can extend the MEB from the existing main CU?

 

[telectrix]

nothing to stop you using your TNC-S earthing for the garage. if you use a TT for the garage, you will be relying on the RCD for fault protection rather than the MCB/s. if using SWA, you don't need RCD protection for the SWA, i prefer to duct the SWA in plastic. 1. for extra mechanical protection. 2. to facilitate replacement ,say, with a bigger cable in the future if load demand increases.

 

[wade88]

So what do i need to do in regards to the TNC-S earthing in te garage? Run 10mm CPC from the MET to the Garage CU?