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js.b1" wrote in message
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17th Regulations require...
#1 Voltage drop within limits for the final circuit type.
Hence cable size must be suitable for the 35m length so as to minimise
voltage drop.
#2 All cables must have RCD protection unless Surface Run, 50mm
depth, SWA or BS8436 or Steel Conduit.
If you run FTE in the house to a jn-box then SWA up the garden, that
FTE must be surface run or 50mm depth or in steel conduit or have RCD
protection at the house-end rather than shed end. Having the RCD at
the house-end means an earth fault on the garage power would take out
the lights so you may want an emergency light in the garage if using
circular saw.
Some people run SWA all the way to the house CU, but in some cases
this can be very difficult (solid floors, space).
There is a uk.d-i-y FAQ available - worth reading.
35m is quite a long way - I assume that includes the run inside the
house to the CU.
If you dropped to 16A radial in the shed and 6A lighting you could
design for a 16A supply (16A RCBO in the house) which would probably
make 6mm SWA doable. 16A is quite reasonable unless your garage is
actually a workshop with lots of power tools in use. For 35m the
garage is most likely going to be a TT supply, ie, 2 core SWA with
garage local earth rod.
Thanks for the reply..
I was planning on MCB protection only in the house, as it is going to be SWA
from the CU in the house to the CU in the garage (Well, the SWA would
connect to an adaptable metal box under the CU, then I would connect a 10mm
earth cable from this using, a piranha nut, to the main earth terminal
Then run the L&N to the CU in round plastic conduit (Probably about 15cm).
I would then have a small CU in the garage containing a main switch, a 6A
MCB for the lights (run surface, in round conduit) and a 20A RCBO for the
sockets (Again run surface, in round conduit) - I don't see the need for an
RCBO in the house, as that means the whole supply would go off, including
the lights, if there was a problem with sockets, and a trip to the house
would need to be made to reset it.
I would also add a 16A MCB for a possibly future freezer.
The distance between the house and the garage is about 15m, so I was
planning on exporting the earth, using the amour of 2 core SWA, is that
unreasonable for an exported earth?
Toby...