Electrical Regulation Advice for separation of a single supply to a dwelling.

[Nuttyboffin]

We have a large flat that was split into two dwellings 3-4 years ago. Both dwellings had the wiring seperated and hence 2 new consumer units installed. The tails for both dwellings remained fed by the existing meter / mains supply to the property. I have recently had an addition new meter installed so that both dwellings are on sperate metered supplies and hence be billed seperately from their chosen utility company. I have run a 25mm Twin / Earth armoured cable the 12 meters between the new meter and consumer unit and plan to use a 60amp metal clad fused switch between the armoured cable and the new supply at one end and another 60amp metal clad fused switch and the tails of the consumer unti at the other end. I used to work for an electrician many years ago and I am competent to make all the connections safely. Question I have is am I permitted to do this under the latest regulations? If I understand the regs correctly I believe I am not allowed to connect new circuits from the consumer unit, some circuits in bathrooms or fit a new consumer unit. The work I am doing appears to sit outside of these three exceptions. Any advice would be much appreciated.

 

[flameport]

What you are proposing to install is likely to be considered a new circuit, and therefore notifiable.
However as no one other than electricians bothers to notify anything, and nothing ever happens as a result of the non-notification, it makes no difference whether notified or not.

In any case, why do you want a switchfuse at each end of the cable?
Why is this 12m long cable needed anyway - how is the consumer unit connected to the meter now?

 

[Nuttyboffin]

The existing supply has a 60 amp metal clad switched fuse at either end of the existing armoured cable and was already in place when I took on the place. One benefit is that the armoured cable gets anchoured to a strong metal clad box and provides terminals for the earth bonding at both ends. I don't see what the benefit of the fuses is, other than reduction from the 100amp one that National Grid have on their main junction. I have basically run an additional armoured cable beside the existing one and copied the set up with the metal clade fused switches. The armoured cables run under the floor of the communal area and out under a concrete pathway leading to the dwelling outside.

The two existing consumer units have tails running to seperate terminal blocks for live and neutral. A sinlge set of tails then go into a 60amp metal clad box which is in turn connected to asingle 2 core twin and earth armoured cable, which runs outside under the concrete path and back inside under the communal floor, up through floor and into another 60 amp metal clad 60 am switched fuse, then tails into the National grid supply.

Many thanks for your help.

 

[Adam_151]

I don't see what the benefit of the fuses is, other than reduction from the 100amp one that National Grid have on their main junction.

The supply authority will not let you rely on their cutout fuse to protect an unknown (to them) length of submain you have installed. So you require a switchfuse at the start of the run, so their cutout fuse is only protetcing a max of 3m of DI tails. You don't however require a switch fuse at the end of the run, it is pointless. If the consumer unit is not capable of taking the armoured, either replace it with one that is, or terminate in suitable adaptable box etc.

I have basically run an additional armoured cable beside the existing one and copied the set up with the metal clade fused switches.

One should be wary of copying that which exists already, unless one is sure that it is correct in the first place!

You are installing a new distribution circuit. This is notifiable work. I see nowhere that the SI limits itself to final circuits only, it merely refers to a circuit, which must catch both distribution and final circuits within its definition.