Your feedback on regulation issues

In a proper tag, the copper and crimp would be covered by plastic or heatshrink tube in the normal way for insulation.

This is just to push this up the list. I have received a few comments but would like a lot more. There must be more worries out there.

An alternative approach would be to bring the tails in from the top or even the side.


I think that the tails would have to be manufactured with the wee shepherd's crook on the end, otherwise two connexions have to be made. I also wonder whether existing main switches' terminals are intended to accommodate solid tails. Given that the line busbar is inserted in the opposite end, I don't see why not.

In a manufactured version there would be a single crimp socket for the tails cable Chris, this is to show the idea, and making a crimp socket from scratch rather difficult, thus the butt connector. Crimp connections are very reliable, and the copper bar clamps very firmly in the devices, there is nothing that can move to a different position if the tails are moved, so the screw is very unlikely to come loose, as you say just like the busbar. The hook is made to completely fill the terminal, it really cannot move. The speed advantage over trying to bend and fit the tails is considerable, perhaps 30 seconds to crimp, 30 more to insulate, and a few to tighten the cable clamp. Bending the tails for side or bottom entry can be quite difficult without the gadget, and the clamp is never as secure as one might like, and twisting the conductors is not very easy once shaped to fit. They never fill the terminal fully so can always move around.

Didn't one of the manufacturers come up with similar-ish solution a few years ago - basically it was a pair of DIN rail mounted terminals sat next to the incomer (perhaps even with twin screw terminals for the tails entering from the bottom) and then some links from the top of the terminals to the incomer's top terminals. Admittedly that retained the screw terminals rather than crimp to the meter tails - but that does allow some flexibility in re-using exiting tails and/or avoiding (possibly dubious) on-site crimping.


   - Andy.

"The size of the main fuse up to 100amp has always been considered safe"

The size of ANY DNO service fuse has always been considered safe.

Oh don't tell me, the guide book is trying to change history again!!!

Regards UKPN.

Andy, you have the wrong idea there. Onsite crimping is not "dubious" in any way, with the possible exception of being carried out by untrained monkeys. It is widely used in ALL bigger installations, one does not clamp 630 mm2 conductors under a screw, or even put them in some form of terminal, they bolt on with a crimped lug. Tails cables are an oddity in 100A supply installations, really the terminations are rather poor as we sometimes witness, and studs and crimped lugs would be a much better design. That is simply what I am trying to do in a way which does not need redesign of all the components of a CU.

Of course all sizes of fuses are safe. It is the backup ability which is important for CUs, see the specification of the CU. The requirements for other switchgear are different, in breaking capacity and protection.

David, looking at it from another perspective in that if we don't seem able to get 'electricians' to strip a cable, form it into position, tighten a screw and then do a pull test to see if it will pop out what chance a decent crimping tool and technique will be used. 

I still can't see why tunnel terminals with 2 screws can't be used in the main switch as this suits our cable type.