DP sw needed on power feed. ?

[Osprey]

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

Just a quick sanity check =85 At the head end .. I have an exiting 100A switch fuse for house supply=85 taking feed from that to an insulated Din rail box, in which I will feed a 30mA RCD (80A) then a 30A HRC fuse =85 the output of that will be connected to the armour cable.

This seems safe & logical to me =85. 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=92s DP sw.

[Andy Wade]

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

[John Rumm]

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

[neverwas]

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?

[Rick Hughes]

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