I am running a feed to external building ( see thread on sub-main
earthing )

Just a quick sanity check …
At the head end .. I have an exiting 100A switch fuse for house
supply… taking feed from that to an insulated Din rail box, in which I
will feed a 30mA RCD (80A) then a 30A HRC fuse … the output of that
will be connected to the armour cable.

This seems safe & logical to me …. Is there any requirement to have a
DP switch on this box?, or is the fact that the feed is via my own
switch fuse, which is within 100mm allows full 'local' disconnection
from supply.

I can use the RCD to provide DP disconnection of feed should I wish to
turn outbuildings feed off for any future service reason.


Just significantly cheaper to use an insulated 4 way IP65 Din box,
rather than fit a 6 way CU with it’s DP sw. http://www.tlc-direct.co.uk/Products/WYWBE4.html

Osprey wrote:

Just a quick sanity check …
At the head end .. I have an exiting 100A switch fuse for house
supply… taking feed from that to an insulated Din rail box, in which I
will feed a 30mA RCD (80A) then a 30A HRC fuse … the output of that
will be connected to the armour cable.

This seems safe & logical to me …. Is there any requirement to have a
DP switch on this box?

No. It's perfectly acceptable to use the RCD as a DP isolator, provided
it has facilities for locking-off.

--
Andy

Osprey wrote:

Just a quick sanity check …
At the head end .. I have an exiting 100A switch fuse for house
supply… taking feed from that to an insulated Din rail box, in which I
will feed a 30mA RCD (80A) then a 30A HRC fuse … the output of that
will be connected to the armour cable.

This seems safe & logical to me …. Is there any requirement to have a
DP switch on this box?

The RCD is safe to use as an isolator switch - they have the required
contact separation, and are double pole.



--
Cheers,

John.

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No. It's perfectly acceptable to use the RCD as a DP
isolator, provided it has facilities for locking-off.

I've noted from past posts the point about "locking-off" but
am not clear if for new installation it must be built in.
Is it [still] OK to proceed on the basis that it will be
locked off using one of the plastic accessories which goes
over the switch with a hole for a padlock?

--
Robin

"John Rumm" wrote in message
news:_tednXdFJrV8xYzVnZ2dnUVZ8radnZ2d@plusnet...
Osprey wrote:

Just a quick sanity check …
At the head end .. I have an exiting 100A switch fuse for house
supply… taking feed from that to an insulated Din rail box, in which I
will feed a 30mA RCD (80A) then a 30A HRC fuse … the output of that
will be connected to the armour cable.

This seems safe & logical to me …. Is there any requirement to have a
DP switch on this box?

The RCD is safe to use as an isolator switch - they have the required
contact separation, and are double pole.



Cheers guys ... means I can use the nest (& cheap 4way boxes)