Farm installations, division of circuits.

streamer · Jun 19, 2017

Good evening everyone.
I live in a rural area and as such get asked to do work on farms so I'm looking to find out how others go about certain types of farm installations.
I find the division of circuits quite difficult without spending a fortune on switch gear and RCDs, especially on 3 phase installations.
For example, I've been asked to look at a new grain shed. There will be a new sub main to the shed protected by a 300mA s type rcd. There will be lighting, 13 amp sockets, a three phase 16 amp socket for a roller shutter door and three more 16 amp three phase sockets for portable fans. As all sockets below 32 amp have to be protected by 30 mA rcd, the easiest (cheapest) way is a to put a 30mA rcd main switch in the DB to be installed in the new shed. However that's not ideal as a fault in a light, for example, could knock the whole shed off. The alternative would be to put RCDs at each 3 phase socket but that starts to get pricey! I haven't come across 3 phase rcbo's but they would probably be an option.
Any ideas gratefully received!

PS. I've been on the forum for a while now and have enjoyed reading the variety of posts here and have picked up a few tips along the way which I am thankful for but just realised that my profile was incomplete so I've updated that now.

davesparks · Jun 19, 2017

If using Schneider acti 9 (formerly Merlin Gerin) then you can add a 'vigi' trip unit to an MCB to add RCD protection to the unit.

Otherwise just use socket outlets with RCD's incorporated.

streamer · Jun 19, 2017

Thanks Dave

davesparks · Jun 19, 2017

I should add that using the Schneider vigi trip units is probably more expensive than the RCD protected sockets.

There's a great family run company online called distribution zone who are very competitive on prices for such sockets.

westward10 · Jun 20, 2017

I wouldn't be fitting rcd sockets in a grain shed keep the rcd protection at the board. Rcbos cost money, that is life.

streamer · Jun 20, 2017

westward10 said:
I wouldn't be fitting rcd sockets in a grain shed keep the rcd protection at the board. Rcbos cost money, that is life.

Hi Westward. Thanks for responding. Even for the three phase sockets? I hadn't come across three phase rcbos until Davesparks recommended the ones he did. I'm thick skinned enough now to tell the farmers when they have to spend a bit more to do it right so although the cost is a consideration it's not the most important one.