Extending supply from one CU to the next with internal connectors

Just been browsing parts and seen these


Wondering if in some cases they are a more elegant way of effectively splitting the supply to two consumer units.

Run supply into first unit and then use one of these to connect to the second unit. Struggling to get my head around how I would connect inside the consumer unit and maintain a supply capable of carrying ideally 100 amps.

Presumably the bus bar is ok if the connector is next to the incoming device, second board would use another one of these instead of a switch.

Then presumably use a short internal neutral cable from hager or similar from the neutral bar.

Wondering why I haven't seen others doing something like this. I am mainly looking at EV installs.

I assume these are aimed at when CU's are stacked and enabling effectively internal interconnection, where as for me I would probably have the boards next to each other, maybe with a gap. 

  • Hi All

    Thanks for the input so far.

    The part number is IT1002U. https://fusebox.co.uk/products/it1002u/ 

    So the challenge i am trying to solve is finding an elegant way to split the tails when the consumer unit is in a downstairs toilet or in the wall way. Quite often in houses that are less then 5 years old, some less than a year old. Still with split load boards, that I can't connect an EV charger to because they can't share n RCD with other circuits. Some are actually pre wired for EV's.

    So frustrating that electricians are still allowed to install split load boards, in my opinion all new domestic boards should be RCBO or as an absolute minimum have some high integrity ways.

    Informing the customer that their almost brand new consumer unit isn't suitable isn't an easy conversation. Then telling them they need an additional consumer unit, plus a load of trunking to hide cables and Henley blocks isn't great, especially if the existing CU is semi recessed with the tails running in the cavity; i know tails shouldn't be in the cavity but there is one company that wires 90% of the new builds within 20 miles of me and it's their standard practice.

    Also it can be challenging to keep cable lengths short enough for a single SPD to protect both boards. I can get around this with an isolator with built in spd, but this can be expensive

    My thought was that theses connectors would allow me to avoid Henley blocks and just run the cables between the CU;s.

    I agree I hadn't thought about the prongs on the bus bar being thinner. Maybe I should put the additional CU below the existing one and use a CU expansion kit.

  • The part number is IT1002U. https://fusebox.co.uk/products/it1002u/ 

    Yes, got that - too many Alans!

    I shall have a look at alanblaby's Hager boards in slow time.

    One of the problems, I think, is that modern houses are so small. I went to a promotional event for a local housing estate 3? years ago (pre-covid) and they allow 25 m² per person!

    My bugbear is not so much the CU up against the ceiling (whether or not above a WC) but at the regulation wheelchair user's height in a downstairs cloakroom cupboard/wardrobe/WHY which is fine until it gets snuggled up under the family's coats.

    I agree with "high integrity" or all RCBO boards. I think that alarms (smoke or burglar, etc.) should be on a separate RCBO. As a consumer, the cost of all RCBO does not bother me, but we do have the cost-of-living-crisis!

  • The Hager one is a poor option, as if you turn off the first DB, the second is turned off as well.

    But if the first DB's switch is intended to be the "main switch" for the installation, that's exactly what you do want. It's then a lot clearer if the 2nd DB (especially if close to the first) had these blocks instead of switch disconnector - the whole combination acting like one large DB (or CU) (if easier to fit in the shape of the space available).

    Bus-bar wise, apart from the old MK CUs which are now consigned to history, I don't recall bus-bars having any thicker prongs for the incomer - so if 100A going out on one of these devices is likely to be an issue then the incomer is going to have much larger problems. Overall load shouldn't exceed 100A for domestics anyway.

    These blocks are just simple terminals - not fused at all. Most of the larger manufacturers produce them in some form or other. So no chance of fusing neutrals or lacking approval.

       - Andy.

  • We used a lot of these in a recent job. Hager do a combined 2 pole AFDD/MCB, fed by busbars from a RCD. Of course, 2 busbars run along the bottom of the circuit protection, which is fine for the double module AFDD/CB combination, but when a single pole device is used, for example for lighting where no AFDD is required, then there isnt a Neutral connecting bar, the busbar under the circuit protection has to be used, hence one of the KRN190 connectors is used , connected to the neutraal busbar, alongside the circuit breaker on the line busbar.