Single phase socket from 3 phase outlet query

[robgraham]

I've a 3 phase switched outlet on a 32A triple mcb that is no longer being used and I require a single phase 13A standard socket in its place.

I could strip out the whole lot and put in a smaller mcb, etc with an RCD protected socket, but have found that I can get an RCD protected

13A fcu. Is there any reason to prevent me leaving all the 3 ph stuff in place, pick off phase and neutral out of the 3ph outlet to feed the FCU and thence to the 13A socket. This means that I don't have to mess about with the MCB and the 3 ph outlet could be re-activated if required in the future.

Rob

[John Rumm]

You could make up an extension lead with appropriate connector on the source end, and a trailing socket (with RCD if require) on the other end. (caveats about ensuring the insulation on the flex is good for 400V given the proximity in the plug)

[robgraham]

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Extension leads are banned as unsafe, and anyway the extension lead would then be facing the whole output of the 32A mcb. This has to be a permanent 240vac, 13A socket outlet; that's why I was going to put the 13A fcu between the socket and the 3ph outlet, which by the way is a wired outlet with a rotary switch, not a socket.

Rob

[John Rumm]

I was thinking 6" long adaptor lead rather than reach across the room lead!

Chances are 1.5mm^2 flex would be adequately fault protected by the 32A MCB anyway.... (a single socket would impose the overload protection)

Ah, sorry my bad. I got the impression that it was a socket outlet of some sort. In which case, yup a hardwired solution will be better. A fused spur won't do any harm, although may not strictly be necessary if ones follows the rules for adding an unfused spur to a 32A circuit (i.e. no more than one single or double socket).

[robgraham]

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Thanks John - sorry about the confusion - so easy to write something inadequate ! Yes of course the 13A plug fuse protects the line doesn't it. There's not an RCD on the 3 ph line (can you get 3ph rcd's ?) so I'll use an RCD socket.

Rob

[John Rumm]

You can get 3 phase RCDs, although I expect you will like the price of a single phase RCD socket much better! ;-)

[TheOldFellow]

=46rom memory: you have to worry about which phase you choose if there are other single phase outlets within some distance. This is many many years ago for me though.

R.

[Andrew Gabriel]

That never was a requirement, but it's good practice. The requirement was to provide a 400/415V warning label where 3 phase is present and not expected. Not sure if that's still a requirement off the top of my head.

[hugh]

In message , Andrew Gabriel writes

I seem to remember from my (proper) computer days when processor supplies were 3 phase any single phase equipment such as tape decks had to be more than 6ft (arms length) away from any other single phase equipment on a different phase. I think this was to avoid the possibility of a 400v shock. Whether this was a "regulation" or just a "Rule" I couldn't say.

[Andrew Gabriel]

It was often quoted, but was never in the wiring regs.

[John Williamson]

Dunno if it was the law, but in the school physics lab in the 60s, we had three phases, one per bench, IIRC, and it was a right soandso getting all three together to power a linear motor I built. We had extension leads running all over the place.

The safety elves would have had a nightmare if it was tried today.