Combining cables to increase current capacity?

[Chrisknowlesuk]

I have a problem and I think I have a solution but wanted to throw it out there to check it is acceptable..

First floor flat with two fuseboards - 1 24hr and 1 Night time economy. The boards are being supplied by two armoured cables coming from separate isolators/meters (60A) from the ground floor.

No clear identification on the armoured cable but possibly 16mm2.

Looking to have the two existing meters replaced with one and the suppy fuse etc upgraded to 100A.

Instead of running a fresh armoured cable from the ground floor, I was considering whether the two existing cables could be combined and therefore have capacity for the increased load?

Taking 25mm2 tails out of the new meter into Henley Blocks and have the Live & Neutral from each existing armoured cable combined and the arrangement reversed at the fuseboard.

I hope I've explained myself clearly there.

Ran this past Niceic technical support and they suggested it was feasible..

 

[ImpededLoop]

Another option would be 2 on peak boards, thus keeping the 2 submains separate, but fed from the on peak supply.

 

[buzzlightyear]

Looking at the what you want the meters
Down on the ground floor you would need to speak to the DNO sub mains isolation.

 

[Chrisknowlesuk]

Another option would be 2 on peak boards, thus keeping the 2 submains separate, but fed from the on peak supply.

Thats a good idea.

The purpose of the upgrade is to install an electric boiler which would be on a 63amp breaker.

I suppose the meters could be upgraded to 80amp ( and both on peak). One board purely supply the boiler and the other one to cover the rest of the flats electrics?

I cannot identify the size of the armoured cable coming off the existing meters but it surely must be no less than 16mm since it is isolated with a 60amp fuse?

 

[ImpededLoop]

Thats a good idea.

The purpose of the upgrade is to install an electric boiler which would be on a 63amp breaker.

I suppose the meters could be upgraded to 80amp ( and both on peak). One board purely supply the boiler and the other one to cover the rest of the flats electrics?

I cannot identify the size of the armoured cable coming off the existing meters but it surely must be no less than 16mm since it is isolated with a 60amp fuse?

That sounds easier than trying to get 2 submains into a domestic consumer unit. You should be able to split the tails after the on peak meter to supply both switch fuses.

 

[Rockingit]

If you're able to gauge the length of the cables then you can work out the conductor csa by doing some continuity resistance sums - look in the on site guide for the copper values. However, some calipers aren't expensive to buy, nor is finding some scrap 10 / 16 / 25mm to offer up and compare!

The requirements for conductors in parallel are that they have to be the same length, csa, material type and be fed from the same OCPD. You also in your case have the infamous 3m rule to consider so instead of using a Henley you might want to use a suitable size KMF instead (or have the KMF upstream of a Henley would probably be much cheaper and neater, although you'd still need to gland the SWA's off....)