Intresting fact about meter tails

[Wotsit]

After worrying that my bulk order for meter tails was the wrong size i found this info, hopefully it will help sombody else

See the full page here:

Q & A of the Day - meter tail sizes - Voltimum UK - Electrical Installation Products and Contracting


Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, on meter tail sizes in the domestic environment, is answered by BASEC:

Meter tail cable - which size to use?

Question: A dwelling in which I am working has meter tails of a smaller diameter than the 25mm2 sample I take around with me. The diameter of the inner insulation appears to be the same as the diameter of the copper conductor of my 25mm2 sample. Two questions in fact: 1. What size meter cable do you think I have encountered here?
2. What is the minimum diameter permitted (the meter is no more than 3m from the consumer unit, and the main fuse is a 100A BS1361).
Answer: Cables that are made to the relevant British Standard (generally BS 6004, Table 7) will follow the regular conductor size ranges.
The next size smaller than 25mm2 is 16mm2 (then 10mm2). It may be 16mm2, or your sample may be a particularly generous 25mm2, in which case it might still be 25mm2. The actual parameter we measure is the conductivity of the cable, not the physical dimension, which is purely nominal.
Both sizes (16mm2 and 25mm2) are commonly used for meter tails, depending on the load. Clearly 25mm2 is a better bet for possible future increase of the load. Depending on the load applied, 16mm2 may or may not be adequate. For advice on this matter, consult a body such as NICEIC or ECA that can advise on the interpretation of the Wiring Regulations (which should be followed) in this respect - Dr Jeremy Hodge, BASEC.

 

[Spudnik]

This has been happening for quite some time now,

i have just installed nearly 500M of 10mm T&E and i had a couple of different makes. They were physically different sizes too.

As for tails, its 25mm all day long for me.

I dont install anything else nowadays, regardless of whats upfront.

 

[Wotsit]

Same for me always 25mm. Found the above supprising.

 

[TPES]

I have often looked at some tails and have been unsure if its 16mm or 25mm, As its not always been obvious.. maybe Ive come across some of the odd insulations thickness's on tails making it hard for me to tell..

9 out of 10 times its obvious.. but sometimes i have been thrown.. Now i know why..

 

[boatnik1]

Have come across smaller than usual 25mm in Germany (Manu. Poland) where the individual cores where more triangular shape allowing the cores to nest tighter against each other with virtually no airspace between cores.

 

[Wotsit]

Its surprising to think that if it was a solid core and with a circle a diameter of 5.7mm it would be 25mm2. Or a triangle 7.6 x 7.6 x 7.6 = 25mm2

Did not know that triangular cable was available that small

 

[Spudnik]

Have come across smaller than usual 25mm in Germany (Manu. Poland) where the individual cores where more triangular shape allowing the cores to nest tighter against each other with virtually no airspace between cores.

There are some SWA's available with this core construction.

 

[boatnik1]

There are some SWA's available with this core construction.

I've used them Jason.

Maybe I didn't explain that I meant the individual strands in a single core were shaped to give a cross section virtually equal to a solid conductor.

 

[kung]

Same here always use 25mm for single phase.

 

[lurch]

so if I come across a flat witha 60a hrc fuse and the tails are 16mm , I should look to upgrade to 25mm????

 

[Spudnik]

so if I come across a flat witha 60a hrc fuse and the tails are 16mm , I should look to upgrade to 25mm????

Ideally yes, although does depend on budget etc.

 

[lurch]

Jason, why ideally? 16mm tails are rated at 60amps, and there fore technically this is ok.

 

[spark1]

so if I come across a flat witha 60a hrc fuse and the tails are 16mm , I should look to upgrade to 25mm????

No. 16mm2 would be fine; in fact 16mm2 is fine up to an 80A HRC fuse.......25mm2 only necessary if 100A fuse installed...............Incidentally Main cut out fuses marked up at 100A by and large, have 80A fuse elements within.



spark1