meter tail length

[dougal]

Is there a maxium meter tails length as I have a pizza shop that requires the old consumer unit connecting up with the new supply that is seven meters away at the front of the shop.

 

[Apache]

2 or 3 metres off the top of my head. Will need overload protection at that length

RCD if buried.

 

[Apache]

like this

http://cgi.ebay.co.uk/MEM-800KMF-Switch-Fuse_W0QQitemZ260443559696QQcmdZViewItemQQptZUK_BOI_Materials_Supplies_Electrical_ET?hash=item3ca3a55710&_trksid=p3286.c0.m14&_trkparms=65%3A12|66%3A2|39%3A1|72%3A1683|293%3A1|294%3A50

 

[SPECIAL LOCATION]

Is there a maxium meter tails length as I have a pizza shop that requires the old consumer unit connecting up with the new supply that is seven meters away at the front of the shop.

Not in the regs..

But DNO will often specify max permissible lengths without additional isolator & overload protection.

e.g. page 17 OSG paragraph 2.2.3 Meter Tails.

I think 5m is a length at which it is a big no-no for direct connection to meter without isolation.

If you put a isolator & overload protection it effectively becomes a distribution circuit. such that the DNO's cut out is only protecting a short run to your Isolator.

I have done a 16m run from Cut out to Cu,

I used 25mm SWA via an 80A cut out switch.

 

[the doctor]

hi

i am sure 3m is the length without some sort of fused isolator

434.3 (iv) which they cite in relation to 434.2.1(i)

if stuck let them tail into an enclosure with say a 80A DP breaker-you can then run the tails round the house happilyGuiness Drink

 

[green-hornet]

I would normaly isolate any meter tails longer than 2.5 mtrs 3 mtrs is the accepted maximum.

Once isolated then the only restriction is voltage drop.

If RCD is used which I strongly do not recomend on meter tails, you have to allow for discrimination which again makes a mockery of the new 17th edition when additional protection is required.

How can you discriminate with all RCD's that comply with the 17th ie buried in walls less than 50mm having to be 30mA insane I hear you shout.

 

[binky]

What do you guys do about earthing after the switch-fuse??? round here, most people just seem to use the CPC of eg 16mm FTE, which I understand is acceptable, but is it good practice?

Locally 3m is max length, so imagine my surprise when I looked at a new flat conversion with meter tails running to each flat from the underground parking area, straight from the meters. The building is 3 storeys high .

 

[extension15]

Locally 3m is max length, so imagine my surprise when I looked at a new flat conversion with meter tails running to each flat from the underground parking area, straight from the meters. The building is 3 storeys high .

But in reality, that is the norm, is it not?

:|

 

[dougal]

Not in the regs..But DNO will often specify max permissible lengths without additional isolator & overload protection.

e.g. page 17 OSG paragraph 2.2.3 Meter Tails.

I think 5m is a length at which it is a big no-no for direct connection to meter without isolation.

If you put a isolator & overload protection it effectively becomes a distribution circuit. such that the DNO's cut out is only protecting a short run to your Isolator.

I have done a 16m run from Cut out to Cu,

I used 25mm SWA via an 80A cut out switch.

so would you give this a separate cert and another for the CU?

 

[Apache]

so would you give this a separate cert and another for the CU?

Sounds a bit overkill to me Craig.

 

[wozz]

Ive always thought it comes down o your DNO, speak to them and see what they say. I know around here they dont like much over 3 meters (the EDF man said "its not like im going to get a tape measure and check") but ive heard others allow longer.

In the past i have worked on flats that were supplied by 3c 25mm SWA, terminated in to trunking and made off straight into the meters. DNO and main contractor were fine with this as no one wanted a ryefield(spelling) board.

 

[binky]

so would you give this a separate cert and another for the CU?

If you look at certs there is a bit about not being directly connected to supply, and top line of NIC certs has black box for distribution circuits.

 

[a1]

What would be good is, if you guys could E-mail your local DNO and ask for their preferrence on it.

IE: What is the Maximum length that they allow? And what is the length before they say to add protection to the tails?

Then post the replies on a dedicated thread.

 

[Evans Electric]

We have always worked on 2 metres here . It must be from the 15 edition, over 2m we fit a fused isolator . ( Push it to 3m sometimes ,but don't tell anyone)

 

[dougal]

i have had an email back from NEDL saying

"Thank you for your e-mail, you will need to speak to your own electrician this is something that we don

 

[Badger]

oh well sounds like directly to the supply it is then

 

[Andy™]

i have had an email back from NEDL saying "Thank you for your e-mail, you will need to speak to your own electrician this is something that we don

 

[Evans Electric]

i have had an email back from NEDL saying "Thank you for your e-mail, you will need to speak to your own electrician this is something that we don

 

[binky]

Have had cause to re-visit this subject and phoned Western Power ref. some new build properties with very long meter tails indeed (4 stories high flats).

It would seem that someone challenged the DNOs right to not connect anything longer than 3m without a switch-fuse, and DNOs lost, so you can now have meter tails as long as you like without Sw.fuse effectively protected by Cut-out fuse only. Needless to say DNO not happy as their fuse is to protect their cables / stuff not anything beyond meter,. but that is the current situation, till something goes wrong!!!

 

[tom1]

http://www.talk.electricianforum.co.uk/showthread.php?p=76893#post76893

i was on this post befor. thanks for clearing it up. its prob a good idea to put isolator in if your doing out with tails.