On Wednesday, 4 July 2018 23:06:38 UTC+1, John Rumm wrote:
On 04/07/2018 19:39, tabbypurr wrote:
On Wednesday, 4 July 2018 15:08:25 UTC+1, John Rumm wrote:
On 04/07/2018 14:58, tabbypurr wrote:

was going to go for a Wylex NM CU, but with all the required
RCDs there won't be enough ways left. If a different CU is used
it will add hundreds to the cost due to need for new RCDs/RCBOs.
So... could this lot be split into 2 CUs? How?

Multiple CUs is probably the way I would go - the number does not
really change the principle of what you are trying to do (much -
although note that previous comment about having a terminal to use
as a neutral).

You could probbaly do a large CU for the head end with sumbmain
feeds, and say a couple of rooms. Then a second smaller one for the
next two rooms.

How would I feed the secondary(ies) from the first CU? Ie what
electrical protection would the interconnecting cable need?

They would be fed from the return sub main from the meters. If they are
also surfaces wired then they don't require 30mA trip RCD protection. So
a type S 100mA trip device as main switch in primary CU. MCBs on feeds
to meters. Returns from meters feeding whatever you decide to go with
(RCBOs etc)

I'm not sure that would work. It needs 4x RCDs total, doing the above would not farm any of the RCDs out to the 2nd box, so wouldn't enable use of 2x split CUs. I'd still need a box with 4x RCDs, and haven't seen any.


This 21 way might do the job, though it comes with the wrong RCDs:
https://www.screwfix.com/p/wylex-21-...mer-unit/2503j

Might be better buying an empty CU and reusing what you can and buying
what extra devices you need.

On second look I realised I could work it with the RCDs supplied, and 21 ways is just enough. So maybe I've found the right CU at last.

Didn't like the prices of industrial units.


NT