On 30/06/2020 22:25,
wrote:
I have a sub-main to a remote socket with a TT earth and, currently, the
SWA braid is terminated on a plastic enclosure. I need to change the
enclosure to metal so have to find a way to terminate the SWA braid
without connecting it to the metal enclosure. This must be a standard
problem with a standard solution, but it's not one I've had to deal with
before so I don't know the "standard solution" :-(
The standard in the past would have been what you have - an insulated CU
at the TT end. With a move to "non combustible" (e.g. metal) CUs for all
things that is more difficult.
Answers I can think of: 1 terminate on a plastic box attached to the
metal enclosure (not ideal in this application),
Yup that is commonly done - an adjacent plastic box etc
e.g.
https://www.tlc-direct.co.uk/Products/LB9025.html
2 cut-off and insulate
the braid and use a standard nylon gland (loss of some mechanical
protection, but I could clip the cable to the metal enclosure), 3
It would work.
There are actually "insulated" SWA glands available that maintain the IP
and mechanical protection:
https://www.etscablecomponents.com/c...b348-b348.html
(no idea on price or a supplier though)
isolate the head end of the SWA and connect the remote end to the TT
earth (easier to do because it comes through a plastic enclosure, but it
doesn't "feel" like the right approach)
That is fine if you have RCD protection at the origin of the submain -
then a fault to the TT earth, would still disconnect the power. It would
not be practical if the submain is fed only from a Fuse/MCB, since you
are unlikely to have a low enough earth loop impedance to reliably trip
the circuit protection under fault conditions.
--
Cheers,
John.
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