Square peg round hole.......

Michaelwgroves · Dec 27, 2017

I'm looking at running 25mm SWA to supply secondary CU to future proof HMO design. See my previous threads for details House of Multiple Occupancy Design - https://www.electriciansforums.co.uk/threads/house-of-multiple-occupancy-design.124817/

My issue is a 100A CU and SP Distribution boards seem to only have 16mm neutral terminals from what I can find. So I'm stuck, can you buy bigger terminals, if not what about placing Henley block in CU/SP Distribution board to run main neutrals. At the risk of being scalded, dare I say drill out to accommodate 25mm ?
Otherwise only solution would be to buy 3Phase which seems like massive overkill for what I'm looking to do.

Deleted member 26818 · Dec 30, 2017

Lucien Nunes said:
Looking at the other thread, it's an HMO with 12 rooms that might be separately let. If the communal GCH packs in. 12 x 2kW fanheaters will go on. There are also some electric hobs.

Returning to the subject of terminating 16 & 25mm² in DB's, we sometimes have to do this where the cable has been selected for VD or running through very high ambient temp. A terminal pin is OK, it won't automatically reduce the CCC, but then typically you won't hit the CCC with the kind of outgoing way you will have in a regular 60898 DB. Beware the effect of poor quality terminals though, sometimes they don't hold well on a solid lump of copper. Tthe same is true of solid MI cores which can be a problem to terminate in marginal single-screw terminals.

An alternative is to use an inline uninsulated butt crimp sized for the SWA core, with a tail of smaller cable with the correct number of strands carefully doubled over inwards, so that all strands contact the crimp. A suitable length tail will allow flexibility to minimise stress on the terminal.

I have been known, when pressed, to put three strands in one hole and four in the next, but I don't recommend it. I would be more likely to do this on an outsize EC, where it also gives the advantage of redundancy.

FWIW here's a pic of a 60898 board with 3x 3-phase 50A outgoing circuits in 16mm², admittedly conduit cable. I didn't wire the straggly stuff in the background, only the 16mm.
View attachment 39943