25mm^2 sub-mains cable type?
Clive Elsmore
>Your wisdom greatly received!
Or even "gratefully"!
Clive
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Frank Erskine
<Clive....@jet.uk> writes
>Hello!
>Does anyone in the Group (or Bill, Matthew; I know at least
>you'll be reading this!) have any knowledge about what kind
>of cable is commonly used to connect the meter to distribution
>box? I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
>Is there a standard cable, or do I have to use separate
>twin-sheathed single cores for the L&N? It will be mostly
>under floorboards - I don't think it needs armouring.
The correct cable to use is separate sheathed singles - armouring isn't
necessary (unless you have vermin under the floorboards) :-)
You should be able to get the meter tails at any electrical wholesaler -
it isn't exactly very cheap though :-(
--
Frank Erskine
Sunderland
Christopher Hall
>Clive....@jet.uk (Clive Elsmore) wrote:
>>Your wisdom greatly received!
>Or even "gratefully"!
>Clive
Hi there!
As I understand the regulations, there is a maximum distance between
the meter and the Main Switch (in the consumer unit) of about 1m. The
Electricity Supplier will connect only short tails to the meter
(although you generally have to supply the cable).
If you want to locate the consumer unit remotely from the incomming
supply and meter you must place your main point of isolation (switch)
and preferably a form of over-current protection (either MCB or HRC
fuse) close to the meter. You can then extend the output of this
switch, which becomes a sub main, to your consumer unit.
I had to do this when we had an extension built and the wall to which
the incommer was atteached had to be demolished.
I burried a conduit from the pole to the point on the outside of the
house where we wanted the meter cabinet moved to and mounted a
weatherproof box with lockable hinged door below it. In this box I
mounted a 100mA RCD and 63A MCB (plus another 30mA/16A combined
RCD-MCB (RCCBO) for an outside socket and some other equipment) and
wired to the consumer unit in 16mm^2 twin + ECC. In our case we
calculated that a 63A supply was sufficient and thus 16mm cable was
OK.
If the sistance between main switch and distribution board is long you
will have to do a voltage-drop calculation, a prospective short
circuit current calculation, and a fault-loop impedance (Line-Earth
Loop) calculation to determine the size of cable necessary, to use
25mm^2 without the calculations might render the installation outside
of the regulations BS(I've forgotten!) formally the 16th Edition of
the IEE Wiring Regulations.
If you need more information, mail me and I will try to help.
Chris Hall
(opinions are my own, not necessarily those of my employer)
peter.t
>Does anyone in the Group (or Bill, Matthew; I know at least
>you'll be reading this!) have any knowledge about what kind
>of cable is commonly used to connect the meter to distribution
>box? I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
>Is there a standard cable, or do I have to use separate
>twin-sheathed single cores for the L&N? It will be mostly
>under floorboards - I don't think it needs armouring.
According to the latest IEE Regs, if the length of meter tails is more
thatn 3m then a 100A HRC double pole switch fuse must be installed
adjacent to the meter.
You can get 25mm.sq. twin and earth cable but is is a s** to work with
and you will still need a 16mm.sq. earth cable as the earth conductor
in the T & E is not big enough. When my sparks did the same job for
me he used armoured cable as the terminations made a good connection
to the Metalclad switch fuse and the distribution board.
Beware, if you don't do it right the Electricity Company will either
not connect the new tails or disconnect it if done by *another*.
Peter T
[pete...@ukonline.co.uk]
Bill Boyd
Clive....@jet.uk (Clive Elsmore) wrote:
>Hello!
>Does anyone in the Group (or Bill, Matthew; I know at least
>you'll be reading this!) have any knowledge about what kind
>of cable is commonly used to connect the meter to distribution
>box? I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
>Is there a standard cable, or do I have to use separate
>twin-sheathed single cores for the L&N? It will be mostly
>under floorboards - I don't think it needs armouring.
>Your wisdom greatly received!
>Clive.
Hi Clive
There isn't actually a standard cable as such - most of us use 6181Y
type cable for the job - singles just like you say (meter tail).
You could use SWA and cut your cost by around half - I think it's
going to be easiest to get hold of, and most practical.
Looking through my trade catalogue (TLC) I reckon that the meter tail
route will cost you about £14/metre. The SWA 25mm 3 core will run at
about £7/metre.
I don't believe that they make a 25mm T&E, and indeed a quick phone
call to my beloved supplier has just confirmed - 16mm is as big as it
goes.
Hope this helps........
From Bill Boyd, at "bi...@mbox.gaiacom.co.uk"
Albion Security Services
http://www.gaiacom.co.uk/users/bill/welcome.htm
David Aldridge
Hi Clive.....
Clive Elsmore wrote:
> [snip] I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
That sounds expensive........ 25 mm "squared" cable would be
very heavy and not very flexible. Isn't that what the electricity
co. would use in its sub-stations? Even 16mm "squared" sounds
excessive in home use!!!! :-) ;-) :-)
Of course, you may mean 25 square mm, which sounds much more
reasonable! :-)
David
--
David C. Aldridge
email: d...@ray.npl.co.uk / emp...@brunel.ac.uk
WWW: http://http1.brunel.ac.uk:8080/~empgdca/
If God had meant us to be naked, we would have been born that way.
If God had intended Man to Walk, He would have given him Feet.
If God had intended Man to Smoke, He would have set him on Fire.
nightjar
In article <4ll2am$7...@postman.jet.uk>, Clive....@jet.uk (Clive Elsmore) says:
>
>Hello!
>Does anyone in the Group (or Bill, Matthew; I know at least
>you'll be reading this!) have any knowledge about what kind
>of cable is commonly used to connect the meter to distribution
>box? I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
>Is there a standard cable, or do I have to use separate
>twin-sheathed single cores for the L&N? It will be mostly
>under floorboards - I don't think it needs armouring.
>Your wisdom greatly received!
>Clive.
>
My local Electricity Board will refuse to supply you if the
distance between the meter and the distribution board
exceeds 2 metres. This is a safety requirement, as the
tails are only protected by the company fuse until they
reach the consumer unit.
I would put a small distribution unit near the meter with
2 x 50A MCBs and connect each to a 10mm twin and earth
cable, as used for cookers, joining them at the main switch
of the distribution board you want to install.
2 x 10mm cables will have the same 100A+ capacity
as 1 x 25mm cable, but are much easier to bend and to
lay. The 16th edition IEE regs are quite happy with a load
being split between two or more conductors, provided only
that they are of equal size. You may prefer to fit 45A MCBs
which give an extra safety margin and are more often stocked
by suppliers. 90A will serve most domestic installations.
Nightjar
Bill Boyd
pete...@ukonline.co.uk (peter.t) wrote:
>According to the latest IEE Regs, if the length of meter tails is more
>thatn 3m then a 100A HRC double pole switch fuse must be installed
>adjacent to the meter.
I should have pointed this out to Clive, but forgot, - it is a very
valid point though.
>You can get 25mm.sq. twin and earth cable but is is a s** to work with
>and you will still need a 16mm.sq. earth cable as the earth conductor
>in the T & E is not big enough. When my sparks did the same job for
>me he used armoured cable as the terminations made a good connection
>to the Metalclad switch fuse and the distribution board.
Where can you get 25mm2 T&E?? When responding to Clive yesterday, I
phoned my three top suppliers, asking specifically if there was such
an animal - each replied no. I didn't think there was either - I've
not come across it in eleven years of practise....
I think 3 core SWA is probably best for this job in balance. 6181Y
meter tails, or even 6941X singles will work out too expensive in cut
lengths, plus the SWA has the advantage of only running one cable
once....
>Beware, if you don't do it right the Electricity Company will either
>not connect the new tails or disconnect it if done by *another*.
The grounds for refusal to connect, or condemnation/disconnection do
vary from board to board, but will only generally be excercised where
the installation is obviously dangerous - e.g. no earth bonding,
incorrect earth bonding, reversal of polarity, potential cable
overload and so on....
Rainer Thonnes
In article <318612...@ray.npl.co.uk>,
David Aldridge <d...@ray.npl.co.uk> writes:
> Clive Elsmore wrote:
> > [snip] I need a 15metre run of 25mm^2 L&N plus 16mm^2 earth.
>
> That sounds expensive........ 25 mm "squared" cable would be
> very heavy and not very flexible.
>
Ahem, Clive didn't actually say "25 mm squared", did he? He used "mm^2",
which by accepted convention means "square mm". It just like with AE's
famous E=mc^2, where the "^2" is taken to apply only to c, not to mc.
In speech, rather than writing, I'd agree, of course, that one should
not use "squared" in this kind of context. In writing, the issue does
not usually arise, since well-understood abbreviations are normally used.
Andrew Gabriel
In article <4m56is$j...@news.gaiacom.co.uk>,
bi...@mbox.gaiacom.co.uk (Bill Boyd) writes:
>
>I don't believe that they make a 25mm T&E, and indeed a quick phone
>call to my beloved supplier has just confirmed - 16mm is as big as it
>goes.
There is a shop in Reading which sells it (or did) called "The Shop
on the Bridge" and also "Milne & Son" (I think first name is the
retail shop and second name is the wholesale part).
They are on Kings Road, opposite ICL's office.
Their prices for most things are very good. Unfortunately, I don't
live in Reading any more.
(I've got no connection with them, other than being a satisfied
customer.)
--
Andrew Gabriel Home: And...@cucumber.demon.co.uk
Consultant Software Engineer Work: Andrew....@net-tel.co.uk
Andrew Gabriel
In article <4m5oqs$8...@s02.pavilion.co.uk>,
nigh...@pavilion.co.uk (nightjar) writes:
>
>I would put a small distribution unit near the meter with
>2 x 50A MCBs and connect each to a 10mm twin and earth
>cable, as used for cookers, joining them at the main switch
>of the distribution board you want to install.
Personnally, I would stear clear of parallel conductors except
ring mains.
>
>2 x 10mm cables will have the same 100A+ capacity
>as 1 x 25mm cable, but are much easier to bend and to
The 10mm cables would have to be well separated so their
heating effects were independant.
Otherwise, if touching, derate by 15% and if separated by
one cable diameter, derate by 6% (see Wiring regs table 4B1).
These are for surface mounted cables; for enclosed cables,
derate by 20%.
>lay. The 16th edition IEE regs are quite happy with a load
>being split between two or more conductors, provided only
>that they are of equal size.
and the same length, so they have the same resistance and
hence carry the same current.
> You may prefer to fit 45A MCBs
>which give an extra safety margin and are more often stocked
They would need to be ganged so it wasn't possible to have
one on and the other off.
>by suppliers. 90A will serve most domestic installations.
Many domestic installations have a main fuse of less than
this. I think 60 and 80 Amps are typical, although the
characteristics of an MCB means it is quite likely to trip
before the fuse blows, depending on the type of fault.
John Stumbles
On 3 May 1996, Andrew Gabriel wrote:
> There is a shop in Reading which sells it (or did) called "The Shop
> on the Bridge" and also "Milne & Son" (I think first name is the
> retail shop and second name is the wholesale part).
> They are on Kings Road, opposite ICL's office.
>
> Their prices for most things are very good.
They seem to have lots of stuff, but the prices I checked seemed more
retail / high street than wholesale: e.g. a set of outside coloured lights
I'd bought at TLC (ex CEL) in Penge were about 20% dearer at the Shop on
The Bridge.
> Unfortunately, I don't live in Reading any more.
Unfortunately I don't live in London anymore :-)
--
John Stumbles j.d.st...@reading.ac.uk
Computer Services, University of Reading http://www.rdg.ac.uk/~suqstmbl
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