Hi all
Am looking for some advice on running a supply to a detached garage.
Some pertinent info:
- I believe the house supply is TNCS
- I have a spare way in the house CU on the non-RCD side
- 15m of 10mm2 T&E (with 4mm2 CPC) runs from the house CU, through the house to the exterior of the house
- ...this connects, via an adaptable box on the outside of the house to...
- 18m of 10mm2 3-core SWA
- ...this runs to the detached garage via a duct, and comes up the inside wall of the garage to where the garage CU will go.
- the garage is a detached double, with stone walls, steel doors and concrete floor. There is no water supply in there at present (maybe a possibility in future, but not now).
- the CPC of the T&E connects to one of the 3 x 10mm cores of the SWA (not the armour) in the adaptable box.
I've a few questions:
1) In the absence of a water supply in the garage, am I OK to export the earth from the house supply, or would I still be better off fitting an earth rod and using a TT system in the garage ?
2) Am I right in thinking that if the equipotential zone had to be exported to the garage (for example if it did receive a water supply), then the 4mm2 CPC of the 10mm2 T&E wouldn't be of sufficient CSA, and therefore I'd have to switch the garage to TT ? (As it would be impossible for me to run a supplementary 10mm earth cable from the house CU area all the way to the garage)
3) I have a spare 50A MCB. From the calcs I've done, I think I should be OK in terms of volt drop and earth impedance. I was planning to use a 50A MCB on the non-RCD side of the house CU, and in the garage, use a MK Sentry "Super Garage Kit" CU with 63A RCD and 4 MCBs. Probably one MCB for external lights, one for internal, one for an internal ring, and one spare way. Does this all sound OK, or is there anything else I need to think about ?
4) If I did export the house earth to the garage, can I do this via the 3rd core of the armoured cable, and run this directly into the garage CU, leaving the armour disconnected at both ends (IE it's just there for mechanical protection) ?
Thanks for any thoughts !
Cheers
Am looking for some advice on running a supply to a detached garage.
Some pertinent info:
- I believe the house supply is TNCS
- I have a spare way in the house CU on the non-RCD side
- 15m of 10mm2 T&E (with 4mm2 CPC) runs from the house CU, through the house to the exterior of the house
- ...this connects, via an adaptable box on the outside of the house to...
- 18m of 10mm2 3-core SWA
- ...this runs to the detached garage via a duct, and comes up the inside wall of the garage to where the garage CU will go.
- the garage is a detached double, with stone walls, steel doors and concrete floor. There is no water supply in there at present (maybe a possibility in future, but not now).
- the CPC of the T&E connects to one of the 3 x 10mm cores of the SWA (not the armour) in the adaptable box.
I've a few questions:
1) In the absence of a water supply in the garage, am I OK to export the earth from the house supply, or would I still be better off fitting an earth rod and using a TT system in the garage ?
2) Am I right in thinking that if the equipotential zone had to be exported to the garage (for example if it did receive a water supply), then the 4mm2 CPC of the 10mm2 T&E wouldn't be of sufficient CSA, and therefore I'd have to switch the garage to TT ? (As it would be impossible for me to run a supplementary 10mm earth cable from the house CU area all the way to the garage)
3) I have a spare 50A MCB. From the calcs I've done, I think I should be OK in terms of volt drop and earth impedance. I was planning to use a 50A MCB on the non-RCD side of the house CU, and in the garage, use a MK Sentry "Super Garage Kit" CU with 63A RCD and 4 MCBs. Probably one MCB for external lights, one for internal, one for an internal ring, and one spare way. Does this all sound OK, or is there anything else I need to think about ?
4) If I did export the house earth to the garage, can I do this via the 3rd core of the armoured cable, and run this directly into the garage CU, leaving the armour disconnected at both ends (IE it's just there for mechanical protection) ?
Thanks for any thoughts !
Cheers