Outbuilding

[AndyD]

I have a customer who has asked me to look at connecting a prefabricated outbuilding. In essance it's basically a walk-in cold room, ie it's a 3 meter by 2 meter room that stands in the garden on a concrete slab and it's built out of 100m styrofoam chromadec panels. It's use is a graphic design studio with 3 Apple Mac computers and an internet router and it came built with preinstalled sockets and lights all on one circuit. They just left a 2.5mm flat twin +e cable hanging out underneath, no subDB.

The customer wants a new external socket in a York box on its own 20Amp circuit from the main DB mounted 1.5 meters away on the wall of the main house and a trailing lead from the prefab room with a plug on the end. I'm inclined to refuse this installation method, the trailing lead would just be laying in the garden. The prefab isn't mobile as such but it isn't fixed either, I asked them if they were planning on shoving it around to other locations and they said they weren't.

My initial thought was to use exactly the same set up with a 20Amp supply to a York box but with an SWA cable hardwired and buried between the prefab shed and the York box.

If anyone has any thoughts I'd be interested to hear.

[GCE]

My initial thought was to use exactly the same set up with a 20Amp supply to a York box but with an SWA cable hardwired and buried between the prefab shed and the York box.

If anyone has any thoughts I'd be interested to hear.

Or surfix which will be easier on his pocket

[Tang]

I would take it straight to the db on a sp+n and label it mixed circuit in outbuilding. If everything is wired with 2.5.

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[Isetech]

I would fit a Weather proof DP with an earth leakage unit, weather proof plug 32 amp 3 pin (industrial type) mounted below the DB on the wall, and run a 2.5 mm trailing cable to the first socket outlets.

If you concerned about damaging the cable, bury it in a conduit.

If you have any problems with the unit, or want to relocate, just unplug, roll up the cable.

A trailing cable is double insulated and designed for that type of application. Sometimes it is better that the cable is exposed, then nobody damages it with a pick or spade.

[AndyD]

Thanks for the comments.

@GCE I would use surfix between the DB and the enclosure on the side of the house. I considered surfix between the house and the prefab but with such a short run there's not much price difference and SWA underground without conduit would actually be an easier and faster installation than cable in conduit for me.

@Tang Yes all the prefab wiring including lighting is 2.5mm CSA so it can be a 20A mixed circuit.

@Isetech The circuit would already have RCD protection in the main DB so no additional needed. There is walkway access around the prefab although going by the overgrowth it's not often used but any surface trailing cable would lay across the walkway so I preferred to avoid this. I did specifically enquire whether they were going to move the thing around and they said not so plugs and sockets would be relatively expensive with no advantage, also with SWA cable it would only be a quick and cheap resin joint to extend the cable if they do change their mind.