garage feed

[sonasardar]

Hi all,
i have re-wired a house to 17th edition,however the feed to the garage was not done because thr ground work was not being carried out.
The senario is this ,the garage is detached ,brick built ,about 10-15 metres from house.the old garage was fed with a 2 core swa i think 4mm buried underground.
i am hoping to use the existing swa ,the garage will have a light and 2x2 gang sockets.
i will have a 2 way metal clad cu in the garage,and hoping to use a metal box in the utility area to terminate swa and from there take a 4mm t&e to the consumer unit in the house on a 40a mcb on the non-rcd side.
Please advise. thanks

 

[Notsosmart]

(From the tables in the back of the BRB);
The maximum current carrying capacity of 4mm T&E clipped direct is 37A (before derating factors and Volt drop is calculated) ~ so if the question is is this okay on a 40A breaker then the answer is no.

Assuming the armoured is 4mm ~ Buried direct in the ground; maximum current carrying capacity is again 37A (before derating factors and Volt drop is calculated) ~ so if the question is is this okay on a 40A breaker then the answer is, again, no.

Have you checked the integrity of the cable? (IR, continuity etc) Is it buried deep enough? You also need to find out its actual csa so you can design the circuit without impunity.

Personally if the ground work is now being carried out and if it is feasable I would try to run in a new 3 core SWA back to the board (no need for an extra joint and the design is easy to control)

If it isn't feasable to run in a new cable if you then use the existing I would feed from 20A breaker in the CU & as its only a 2 core I would install it into an RCD putting in an earth stake at the garage, then as its only lights and a couple of sockets; from sub board with a 16A socket radial & a 6A lighting circuit in the garage.

 

[nick22]

Hi
Just done a periodic however found the following:-
6mm 3core swa cable from unprotected side of CU to garage metal clad dis-board earth used in swa and terminated in garage dis-board, I usually leave earth of swa disconneted at garage end and supply earthrod and garage end.

QUESTION - Can the earth of the swa cable be used to supply garage dis-board, 6mm 3core supply using 3rd core as earth, PME system at mains.

Hi again

PME Supply--->---House disboard---->---6mm swa 3core cable, 15 mtrs away from house--->----garage disboard metalclad

 

[sonasardar]

Thanks the reason for the extra connection box in the utility is so that the armoured cable can be made ( glanded) and the earth from t&e carrying on to the CU in the house.

 

[Guest123]

Hi
Just done a periodic however found the following:-
6mm 3core swa cable from unprotected side of CU to garage metal clad dis-board earth used in swa and terminated in garage dis-board, I usually leave earth of swa disconneted at garage end and supply earthrod and garage end.

QUESTION - Can the earth of the swa cable be used to supply garage dis-board, 6mm 3core supply using 3rd core as earth, PME system at mains.

Hi again

PME Supply--->---House disboard---->---6mm swa 3core cable, 15 mtrs away from house--->----garage disboard metalclad

Depends if there are any additional services in the garage i.e water, gas. Is there any exposed steelwork, the frame of the garage for instance???