IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Meter Tails Size
Topic Summary:
Created On: 09 February 2013 04:21 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 09 February 2013 04:21 PM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Hi

In short, I'm applying for a new job, and wanted to refresh myself. So I bought the new scaddon book.

I've found a few incorrect figures in the book (maybe misprints), but this one has been quoted twice, and I'm sure I'm right.

Can anyone tell me. The Main incoming Tails, to carry 137.2 Amps, is 35mm isn't it? Not 25mm as it says in the book. If it is 25mm... why?

The regs say, on for 141 amps, its 35mm. Ok if free air, horizontal, you can get away with 25mm.

Any light on the subject would be appreciated. As I'm sure I'm right...
 09 February 2013 06:11 PM
User is offline View Users Profile Print this message



perspicacious

Posts: 7128
Joined: 18 April 2006

Welcome Ady

Perhaps the author has considered that Note 1 to Table 4E1A isn't applicable.......

Regards

BOD
 09 February 2013 06:13 PM
User is offline View Users Profile Print this message



ssohnoherewego

Posts: 63
Joined: 07 March 2008

His books are renowned for containing mistakes.
 09 February 2013 06:38 PM
User is offline View Users Profile Print this message


Avatar for UKPN.
UKPN

Posts: 463
Joined: 17 January 2012

25sqmm @ 100amp
 09 February 2013 07:04 PM
User is offline View Users Profile Print this message


Avatar for sparkingchip.
sparkingchip

Posts: 5820
Joined: 18 January 2003

I seem to remember a cable calculation in one of his books ending up with 16mm T&E for a 3Kw immersion heater, it is all to do with installation methods.

Andy
 10 February 2013 03:57 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Hi Bod, and thanks for reply.

In the book, it gives no reasons for using 25mm and and ref Note 1 says on 4E1A, main tails surely will not be subject to 90 Deg C.

I am right then...
He should be using Table 4D1A Method C for Main Tails.
For 137 amps load on the house, it would require 35 mm Tails and not 25mm as that has a max current carrying capacity of 114 amps.

Regards Ady
 10 February 2013 04:01 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Ref mistakes in the book.... i have noticed that a lot.

Makes you wonder sometimes, like this one, am i right or wrong!?!?
You expect a book, to be right, don't you....
 10 February 2013 04:40 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Originally posted by: UKPN

25sqmm @ 100amp


Thanks for reply.

Which table is this from?
On Table 4D1A 25mm is rated at 114a.
 10 February 2013 08:46 AM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11259
Joined: 13 August 2003

I suspect UKPN is referring to the nominal size of the supply, rather than Iz as such (i.e. for a 100A fuse you need 25mm tails by the supplier's rule book).
- Andy.
 10 February 2013 10:02 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Originally posted by: AJJewsbury

I suspect UKPN is referring to the nominal size of the supply, rather than Iz as such (i.e. for a 100A fuse you need 25mm tails by the supplier's rule book).

- Andy.


Hi Andy

Thanks.

And i guess, without looking now, i'll no reference to the suppliers's rule book in the regs.
As long as i'm clear now. Drove me crazy thinkng, thinking this is wrong, surely!

Regards Ady
 10 February 2013 10:03 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Originally posted by: perspicacious

Welcome Ady



Perhaps the author has considered that Note 1 to Table 4E1A isn't applicable.......



Regards

Hi Bod, and thanks for reply.

In the book, it gives no reasons for using 25mm and and ref Note 1 says on 4E1A, main tails surely will not be subject to 90 Deg C.

I am right then...
He should be using Table 4D1A Method C for Main Tails.
For 137 amps load on the house, it would require 35 mm Tails and not 25mm as that has a max current carrying capacity of 114 amps.

Regards Ady


BOD
 10 February 2013 08:50 PM
User is offline View Users Profile Print this message


Avatar for UKPN.
UKPN

Posts: 463
Joined: 17 January 2012

-the "book" is only for the privileged few. but you can trust me, 25mm is 100amp.
16mm is 60/80amp

Regards
 11 February 2013 07:08 AM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Originally posted by: UKPN

-the "book" is only for the privileged few. but you can trust me, 25mm is 100amp.

16mm is 60/80amp



Regards



Thanks for reply, and i agree....
But i still have a question regarding Scaddons theory in his book.

I see how if an 100amp main fuse you'll need 25mm tails.
But he's talking about 137amp total load on the dwelling, so surely in theory; he'd need to upgrade the main fuse?

Ok, I know in practice, the dwelling will not have everything running at once, and the chances of dragging that much power through, to blow the main fuse is unlikely. But he doesn't mention any of this in his book.

Maybe I'm getting too concerned here, as i only wanted to brush up, as doing things day in and out, you kind of get used to doing things.
But thanks again for taking the time to reply.
 11 February 2013 11:54 PM
User is offline View Users Profile Print this message



alancapon

Posts: 5745
Joined: 27 December 2005

You need to ensure reference to the correct "book". Since the privatisation of the Electricity Supply Industry, each DNO has their own book, and there are slight differences between them in what is required. My employer for example requires 25mm² for any fuse size up to 100A.

Regarding 137A for domestic, here you would have to apply for a three phase supply.

Regards,

Alan.
 12 February 2013 02:30 PM
User is offline View Users Profile Print this message



AdyWilliams

Posts: 8
Joined: 09 February 2013

Originally posted by: alancapon

You need to ensure reference to the correct "book". Since the privatisation of the Electricity Supply Industry, each DNO has their own book, and there are slight differences between them in what is required. My employer for example requires 25mm² for any fuse size up to 100A.



Regarding 137A for domestic, here you would have to apply for a three phase supply.



Regards,



Alan.



Thanks for reply.

It does seem that way about which 'Book' you refer to.

Regards Ady
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.