Exporting Power (again)

Sounds OK to me. How were you planned on spurring off the incomer? Presumably you'd need Henley blocks to tap the 100A feed, and a way to pull the cutout because this is before the main switch in the CU? (Unless you have an isolator near the meter). It would also mean the outbuilding is still live when you pull the main switch, which could be surprising.

Do you have a spare way in the CU that you could instead use to tap off from the CU, which would make everything controlled by the main switch? You could put it before any RCDs in the box.

If you did have a spare way (or could rejig things to make one), a 20A RCBO would avoid the need for the internal box and the Henley blocks.

How are you arranging earthing? Are you exporting the earth or fitting a TT earth rod? Are you exporting using the armour or a separate earth core in the SWA? Does the outbuilding have any metal it in (like a greenhouse) or any buried pipes?

Theo

Theo <theom+ snipped-for-privacy@chiark.greenend.org.uk> wrote in news:d+f* snipped-for-privacy@news.chiark.greenend.org.uk:

Initial plan was to slave the feed off the CU isolator but wouldn't be worried about having duplicate tails via henleys, it appears quite common where there are multiple CUs which is effectively what this is. I'd happily pull the main fuse and know enough to do that safely.

There is a spare way in the Crabtree CU and I thought of using an RCBO but I really wanted double pole isolation of the external cable. I could do that with a separate isolator but that in turn could lead to confusion having 2 'off' switches for the outside feed. All being done on a budget as a favour so I'd prefer to use a generic Aviom RCBO but would be worried about the fit in a different CU. Similarly I could put in a 20A MCB with a separate DP RCD in an enclosure. Bending towards these options as it does simplify the supply feed.

Probably shouldn't but I will be exporting the earth, it's not far and it's a wooden structure, no greenhouse or other metalwork. Earth will be via a separate core but with the armour earthed for digger protection.

Thanks for the input.

What sort of CU is it? I have a Crabtree Starbreaker, to which I have retrofitted miniature RCBOs - they are all double pole ... indeed you can Megger the circuit, without disconnecting it and just switching it off.

SteveW snipped-for-privacy@walker-family.me.uk> wrote in news:vdhrqj$2t2mm$ snipped-for-privacy@dont-email.me:

Great news, thank you! My mainly obsolete stock here has only neutral loop thro for current sense so glad to see one with DP. It is a Crabtree CU and poss a slightly older model[1] but I'll take a punt and get the RCBO as it looks no larger than a regular MCB and I have the nouse to adapt the installation if any tweaks are required.

Thanks again, that's saved a lot of effort.

Earth will be> via a separate core but with the armour earthed for digger protection.

So use a MCB at the head end and a RCD in the shed.

That's the whole point of SWA

That's what I did for my brother's shed. MCB in the main CU (not on any RCD). SWA from CU to shed, earthed at CU. SWA earth not connected to anything at shed end. Earth rod and TT system in shed. Shed CU contains 6A and 20A RCBOs for lighting and sockets respectively including outdoor sockets for lawn mower, hedge cutters, etc.

Also laid an underground ethernet cable to shed, and there's an original Raspberry Pi 1B in there which monitors the shed, and adjusts shed environment to prevent any condensing in there (and has been running

Andrew Gabriel snipped-for-privacy@cucumber.demon.co.uk> wrote in news:vdrtbu$r61c$1 @dont-email.me:

Acknowledging your knowledge both, particualy Adam as it is his job, I want DP isolation at the source end and the simplest way to do that is with a DP RCBO in the CU so that is the way I will be going.