100m Cable run

[Coenst]

Afternoon all

I have a task of running a supply from the 3 phase incomer on a farm to a barn conversion 100m away. The blue phase (100A) is free that I will have to run and connect to the 100A consumer unit which recently installed in the barn.

What size armoured will be safe to do so? 25mm?

Any advise is appreciated.

 

[Leesparkykent]

Welcome Coenst. It Doesn't look like you have done any calculations to conclude 25mm?

 

[Richard Burns]

You would need to assess your volt drop over that distance as being the likely limiting factor, so you would need to know your anticipated load pretty accurately to avoid installing too large or too small a cable.
25mm² over 100m would limit you to about 39 A.

 

[Darkwood]

As above show your calculations and any errors we spot we will be happy to correct them for you, we like to help on this forum but stop short of doing all the calculations for you.

 

[shanky887614]

over 100m are you joking, your sub circuits for lighting etc wont comply

 

[uksparks]

What's the design current? 100A? Also is it going to be TT at the remote end?

 

[uksparks]

At s guess, 100A over 100m, you would probably need about 70mm, I've not calculated that, that's a rough guess.

 

[uksparks]

If it was 70mm, that's over half a tonne of cable and over £1500 I should think.

 

[Marvo]

At s guess, 100A over 100m, you would probably need about 70mm, I've not calculated that, that's a rough guess.

Not sure that guesswork will help. What do the tables in the regs say about the appropriate cable size?

 

[uksparks]

I'm watching TV, not looking at regs!

 

[snowhead]

Not sure that guesswork will help.

This post started off with guesswork.

This shows it at 50mm with basic info; Welcome to Doncaster Cables - Technical Help

 

[Leesparkykent]

At 5% volt drop ^^

 

[shanky887614]

This post started off with guesswork.

This shows it at 50mm with basic info; Welcome to Doncaster Cables - Technical Help

At 5% volt drop ^^

lol but then a lot of subcircuits wont comply.

seriously but i would get a quote for a new supply from dno, you might get lucky and there might be a service cable close and at that length and size cable you would need and have sub circuits will be expensive.

70mm is £18m and 95mm is £25 +delivery cost as well


you need to do a proper cable calc, over that distance you haven't got a chance in hell 50mm will comply for supply to the board.

clipped direct would give you 2.7% vd with no derating factors applied so as soon as you put a lighting circuit off it you will be over

 

[Leesparkykent]

lol but then a lot of subcircuits wont comply.

seriously but i would get a quote for a new supply from dno, you might get lucky and there might be a service cable close and at that length and size cable you would need and have sub circuits will be expensive

Thats why you would size the cable accordingly.

 

[btvc-electrical]

Alternatively too one thicker cable you could consider 2 slimmer cables?

 

[Andy78]

Hmmmmm OP not been back with his detailed calcs yet ? I'm very surprised I must say.

I wonder if he stuck to the original method of picking a size out of a hat ? Did he go for the 25, or the 35, perhaps a 50, a 70, or maybe the 95 ?

 

[Darkwood]

Due to the time lag of any response it would seem the OP has seen he is a bit out of depth as he asked a question while providing little if any of the info needed to work it out, clearly he would not be aware about the info we needed.