Hi, I'm planning to cut into the ground floor power cable ring and
extend it into the adjacent, integral garage. The concrete block walls
of the garage will make it necessary to run the cable in conduit
(plastic).

I intend to have one vertical run of 2.5M, with 3 x 2 gang boxes and
sockets contained within this run. I then want to elbow the top and
place another 2 gang box and socket at the end of a 1.5M horizontal
run, which will then form an inverted L shape. To maintain the ring
structure I'll need to return the cable to the extension starting
point.

Is it common practice to return the cable down the same conduit that
it came up in, or is it better to form a conduit loop?
The latter option is going to require twice as much conduit, so I'd
rather use the former method if practical.

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Kind regards,
Geoff Mills