meter tails

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daryl631

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Hi guys just going to start new job meter has been moved by dno what is the max length of meter tails do i work it out the same as volt drop on pvc cables/the meter is now outside new extension and the consumer unit will be in old kitchen about 15meters away

 

dave2

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I recently installed meter tails of over 20m.

NEDL confirmed by email that this was ok.

Dont think this has anything to do with NICEIC.

Dave2

 

extension15

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You could fit a 63A switched fuse link in place...

then length is not too much of an issue (within reason)..

:D

 

seajayess

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I think if the meter tails are more than 3 meters you have to fit a double pole isolator at the service head / meter, also if the meter tails are not installed to 17th. edition ie within earthed protection, SWA ,I think you will require RCD protection for them stand to be corrected CJS

 

DonkeyDong

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Hi there,

Like the guys say, depending on the tail run, it would be best to install a metal fused isolator next to the service head, then run 25mm SWA to the new CU

D.

 

extension15

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I think if the meter tails are more than 3 meters you have to fit a double pole isolator at the service head / meter, also if the meter tails are not installed to 17th. edition ie within earthed protection, SWA ,I think you will require RCD protection for them stand to be corrected CJS
You wouldn't believ how many installations I've been to, with long tails and no isolator...

I think the Service head to meter is one of the most inconsistent and widely diverse areas of installation work (From an inspection point of view)..

:|

 
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There is a regulation in the 17th about the max lenghth of tails without fusing will look it up tomorrow. The last time I did a supply like this I used armoured cable fed from an mem 800 kmf switchfuse placed in meter cabinet. They are 80 amp. SSE guys said supply would need to be downgraded so that 80 amp fuse would blow before 100 amp main fuse. Wylex switchfuses are to big as they take up to much room in meter cabinet.

batty

 

kme

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There is a regulation in the 17th about the max lenghth of tails without fusing will look it up tomorrow. The last time I did a supply like this I used armoured cable fed from an mem 800 kmf switchfuse placed in meter cabinet. They are 80 amp. SSE guys said supply would need to be downgraded so that 80 amp fuse would blow before 100 amp main fuse. Wylex switchfuses are to big as they take up to much room in meter cabinet.batty
Mrs. KME likes KMF`s:x:x:x:x

CJS was correct, in that, if the DB is more than 3M from HED, an isolator must be installed at the HED position. There is no requirement for it to be fused, AFAIK. But It may be advisable to use a KMF, as Batty suggests.

 

SPECIAL LOCATION

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Hi guys just going to start new job meter has been moved by dno what is the max length of meter tails do i work it out the same as volt drop on pvc cables/the meter is now outside new extension and the consumer unit will be in old kitchen about 15meters away
Confirming what some of the other guys have said... Meter tails are just another circuit... From Meter to CU...

Not much different to a large installation or say an agricultural installation.. where supply comes to one building..

and another separate building needs its own Cu distribution...

You just stick in a suitable sub-main, meeting certain requirements to ensure..

Mechanical protection,

Isolation,

Fuse protection,

Volt drop etc.. etc..

Within a house, meter tails with adequate sheathing for mechanical protection

and possibly Trunking or conduit if a longer or hazardous run due to external influences where the cables will be run..

I think the 3m bit comes from general guidance about when you need a separate switch to isolate the tails, not just the main fuse.. But think this is just good practice, not a reg.

The only bits I could quickly find in the big book is...

537.1.4 A main linked switch or linked circuit breaker shall be provided as nears as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

A mains switch intended for operation by ordinary persons, e.g. of a household or similar installation, shall interrupt both live conductors of a single phase supply.
which is a combination of old regs "460-01-02" & "476-01-03"

old regs also had this reg, 476-01-02,

where the last sentence had significance upon the meter tails

 
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When doing 17th edition course remember reading about having to put in switchfuse if tails are more than 3 mtr although i wonder if i dreamt it as ive looked through regs but can't find it.

batty

 

binky

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I've always understood length is denoted by DNO not regs, which in sunny Devon was 3m max although recently seems to have been reduced to 1.5m. However, as no one from western power ever seems to check, and cable fitters don't care, some flexibility is 'allowed'. In these circumstances though, I would treat as sub-main as per other replies above and fit Switch fuse at meter end, after which it would be viable to use 16mm FTE given suitable readings of Ze (follow adiabatic equation to justify earth sizing)

 

daryl631

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Thanks guys will fit two pole switch with fuse and run in metal earthed conduit,sent post about two months ago about moving incoming power cables still waiting for dno to move meter,tails run from outside through extension ceiling into kitchen so i will run in conduit

 
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