Meter Tail length 3 metre theory

[riveralt]

I was under the impression that responsibility for meter tails from the meter into the property were the responsibility of the property owner.
However, the length of the meter tails and cross sectional area must comply with the requirements of the distributor. Sect 434. 3 (iv) red book.

I have a customer whose lives in a top floor (3rd floor) flat whose meter is situated in a ground floor cupboard. He wants to replace and move his current consumer unit about three metres.

I contacted Scottish Power to seek their advice on moving the consumer unit and was told that their responsibility ended at the distributors cut out and that provided the customers cable current carrying capacity exceeded the main fuse then the length of the cable was not a concern. (apart from potential voltage drop)

This seems to put paid to the 'three metre theory' limit on meter tails.

 

[ericmark]

I think the 3 meter rule comes from 434.2.1 and 433.2.2 which says you must protect a cable within 3 meters of a change in current carrying capacity.

I am also under the impression that singles must be either in earthed conduit or max of 3 meters although can't find regulation. In flats I have seen SWA between meter cupboard and consumer unit where it runs for over 3 meters.

 

[ban-all-sheds]

I think the 3 meter rule comes from 434.2.1 and 433.2.2 which says you must protect a cable within 3 meters of a change in current carrying capacity.

provided the customers cable current carrying capacity exceeded the main fuse...

I am also under the impression that singles must be either in earthed conduit or max of 3 meters although can't find regulation.

Meter tails are insulated and sheathed.

 

[holmslaw]

..

 

[JohnW2]

I think the 3 meter rule comes from 434.2.1 and 433.2.2 which says you must protect a cable within 3 meters of a change in current carrying capacity.

As I understand it, that rule is saying that if the cable is less than 3 metres (plus some other conditions) overload protection may be at the downstream end (or anywhere in between), rather than at the point of reduction in CCC. It doesn't say that one can omit overload protection.

There seem to be at several reasons why that doesn't apply to meter tails. Firstly, there is generally no reduction in CCC after the meter terminals (often the opposite!). Secondly, there is usually no real OPD at the CU end of the tails - the only overload protection is usually provided by the MCBs in the CU, the total pre-trip rating of which is probably going to be too high. Thirdly (although this is perhaps a matter of the different regs on the two sides of the meter), if the overload protection provided but the cutout fuse is deemed adequate for the pre-meter tails, it theoretically ought to be adequate for the post-meter tails, whatever their length.

I was under the impression,as implied by BS7671, that it was the DNOs who attempted to impose conditions (length and CSA) of the post-meter tails, even though that's theoretically not their territory! In common sense terms, SWA would seem to make sense for long tails, particularly if they took circuitous routes, because of the mechanical protection and earthed armour.

Westie?

Kind Regards, John.

 

[ricicle]

the 3 meter rule ......max of 3 meters ...........3 meters.

Continuity tester, IR tester and loop tester ?