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Electroglow

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Hi all

I would like your thoughts please on the following subject

When the dno install a metre in the south west they use 80A main fuse heads....

But they only use 16mm tails....

I asked what they use if they put in a 100A fuse

Same size 16mm

So why do we as sparks have to use 25mm tails on domestic property's?

There is no rcd protection from for the tails just a isolation switch??

Always wondered...?

 
to cover our backsides.!?

BTW, I dont always use 25mm tails, depends on the size/loading of the CU or DB as to what size I use, sometimes its only 6mm I use.

 
No nore do I... Like you said I always use depending on the load eg garage supply! I do only use 25mm on domestic tho

For example I have seen a contractor use 95mm tails on a 3 phase 100A per phase supply? I just don't understand?

 
If the main fuse is defo 80A (or less), then it is perfectly legitimate to fit 16mm tails. If the fuse is ever uprated to 100A, then the tails should be changed to 25mm.

If the DNO choose to fit 16mm with 100A then that is their responsibility. They are responsible up to the meter (or cut out if provided).

 
But why... If the incoming size is 16mm? I understand it's good practice.

Just wanted to get my head around it... Always wondered

 
But why... If the incoming size is 16mm? I understand it's good practice. Just wanted to get my head around it... Always wondered
because we are required to work to BS7671. Check the ratings of 16 and 25 mm tails and you'll see it's 87 and 112 amps respectively.

 
Fair enough

---------- Post Auto-Merged at 18:39 ---------- Previous post was made at 18:39 ----------

O. So y use 95mm on 100a 3 phase lol

 
All DNO are different i got pulled up on a job once, new submain to portacabin maximum supply to building would be 40 amps due to design but they refused to connect as i had used 16mm tails and said they neede to be 25mm. I was not there at time but luckily another sparks was available to change them so supply got put in.

 
Hi all I would like your thoughts please on the following subject

When the dno install a metre in the south west they use 80A main fuse heads....

But they only use 16mm tails....

I asked what they use if they put in a 100A fuse

Same size 16mm

So why do we as sparks have to use 25mm tails on domestic property's?

There is no rcd protection from for the tails just a isolation switch??

Always wondered...?
erm..? Have you looked at the on-site-guide???? :C

Meter tails guidance can be found in Section 2.2.3 page 17 of Green On-Site-Guide.

And was previously found in:-

Section 2.2.3 page 17 of Red On-Site-Guide

Section 2 (iii) page 14 of Brown On-Site-Guide

Section 2 (iii) page 14 of Yellow On-Site-Guide...

etc..

They all say

 
I'm not saying can I use smaller...

It was a question as to why do they install 16mm tails and we use 25mm on most domestic cases.

I know the regs stat you have to use 25 mm my question was y?

 
I'm not saying can I use smaller... It was a question as to why do they install 16mm tails and we use 25mm on most domestic cases.

I know the regs stat you have to use 25 mm my question was y?
The Regs do NOT specifically state that you have to...

The guidance suggests the minimum should be 25mm

 
Last edited by a moderator:
Had a 30A in my house when I first moved in. Mid 1030's property and had just been rewired complete with electric cooker, hob and shower. Needless to say it didn't take long to blow it. lol

 


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