Long Distance Electrics
 

Can anyone supply me their view of the 16th edition with respect to
volt drop and current capability.

I am taking a supply from a third party (with their permission) to a
site some 180m away. The third party has insisted that I use 16mm sq
SWA to minimise the volt drop. This I accept.

He has calculated (and I concur) that I will remain in the
"permissible" voltage range if I restrict my load to 8A. To do this,
he is stating that (by the 16th Edition) he needs to fuse the source of
my supply with 8A.

This is where we start to disagree.

I consider that the purpose of the outgoing fuse is to protect the
cable, thus with 16mm sq, I should (in theory) be good for about 90A.
However I shall be prepared to accept 16A that will allow me to run a
welder (albeit at lower volts than upstream).

So, I accept that it is his supply and theoretically he could fuse it
at 5A (if he wanted) but is there anything in the Wiring Regs that says
he must current limit it to prevent me doing damage to my equipment?
Surely if he states that the maximum current I can take is 8A to stay
within the permissible voltage range, if I decide to exceed that's my
problem? (and any damage I do to my equipment is my responsibility).

As it is, the only loads are likely to be fluorescent lights, kettle,
welder (ocasionally), compressor (ocasionally) and step down
transformers to 110v, 24v and 12v (which I shall tap to suit).


Cheers

Peter

How did you calculate the 8A?

My calculations using Ib = 16A, and a voltage drop of 2.8mV/A/m (for 1
16mm^2 conductor) gives:

Voltage drop = 2.8 * 16 * 180 / 1000 = 8.064V.

The limit should be 9.2V so I don't see a problem.

"puffernutter" wrote in message
ups.com...
Can anyone supply me their view of the 16th edition with respect to
volt drop and current capability.

I am taking a supply from a third party (with their permission) to a
site some 180m away. The third party has insisted that I use 16mm sq
SWA to minimise the volt drop. This I accept.

He has calculated (and I concur) that I will remain in the
"permissible" voltage range if I restrict my load to 8A. To do this,
he is stating that (by the 16th Edition) he needs to fuse the source of
my supply with 8A.

This is where we start to disagree.

I consider that the purpose of the outgoing fuse is to protect the
cable, thus with 16mm sq, I should (in theory) be good for about 90A.
However I shall be prepared to accept 16A that will allow me to run a
welder (albeit at lower volts than upstream).

So, I accept that it is his supply and theoretically he could fuse it
at 5A (if he wanted) but is there anything in the Wiring Regs that says
he must current limit it to prevent me doing damage to my equipment?
Surely if he states that the maximum current I can take is 8A to stay
within the permissible voltage range, if I decide to exceed that's my
problem? (and any damage I do to my equipment is my responsibility).

As it is, the only loads are likely to be fluorescent lights, kettle,
welder (ocasionally), compressor (ocasionally) and step down
transformers to 110v, 24v and 12v (which I shall tap to suit).


Cheers

Peter


Well according to
http://www.tlc-direct.co.uk/Technica...ltageDrop.html you will be
safe for use up to 4.5kw, 19amps.

So a 16 amp fuse should be ok.

Matt Beard wrote:
How did you calculate the 8A?

Is the length of the current path 360m (round trip) though ... 16v @ 16A?


My calculations using Ib = 16A, and a voltage drop of 2.8mV/A/m (for 1
16mm^2 conductor) gives:

Voltage drop = 2.8 * 16 * 180 / 1000 = 8.064V.

The limit should be 9.2V so I don't see a problem.

When I looked orginally on TLC-Direct, I thought I saw that it was it
was a maximum 4.4v drop. On revisiting the site I realise that I
misread the calculation and that 9.6v is acceptable. (Which means I can
get 16A and I'm happy!)

All I need to do now is convince the site sparky! (and find out where
he got 8A from!)

(I assume that mV/A/m figure quoted in the regs is for both conductors,
so you are doing "out and back" at the same time.)

Cheers

Peter

"puffernutter" wrote in message
ups.com...
When I looked orginally on TLC-Direct, I thought I saw that it was it
was a maximum 4.4v drop. On revisiting the site I realise that I
misread the calculation and that 9.6v is acceptable. (Which means I can
get 16A and I'm happy!)

All I need to do now is convince the site sparky! (and find out where
he got 8A from!)

(I assume that mV/A/m figure quoted in the regs is for both conductors,
so you are doing "out and back" at the same time.)

I once helped Kango drill in a cave in the Mendips over quite a distance
wired using over 100m of 13A solid core cable. To get 110V at drill end
required over 180V on the surface generator !!!