cable sizing help please!

[steve-irl]

Hi all, just new here today. Just want a few opinions on cable size needed for a cable run from a main dis board to a sub dis board.

It's 3 phase 400/230V system so will be using either 5 core swa or 4 core swa with separate earth. It will be run in buried duct. The cable run is 80 metres between the boards. max load of the entire sub circuit should be about 60 amps, being generous.

Circuits off the sub board will be two 10kW 3 ph motor circuits and three single phase circuits of 4.5kW each.

Have something worked out myself but just want some more opinions as im second guessing myself as not been at this end of things for some time lol.

Thanks in advance!

 

[Sintra]

If there are no lighting circuits to be connected to the sub main 16mm otherwise 25mm if lighting is included.

These are worked out on the load being 60A

 

[steve-irl]

thanks sintra, theres a possibility of lighting being added but would only be 8 or 10 twin fluorescents if it goes ahead.

I had thought of going for 35s to allow for volt drop and allow for some expansion in future. Or am I being way too generous?

do u mind me asking why u said 16s but 25s if lighting is included?

cant get my head together here sorry lol

 

[Sintra]

If lighting is involved then your max volt drop allowed is 3% which would be exceeded on a 16mm and if no lights are involved then your max volt drop would be 5% which would enable you to use a 16mm.

 

[steve-irl]

thanks for clearing that one up. far as i remember the max drop in the irish regs is 4%.

have you got the volt drop formula? just to make sure i was using the right one.

its terrible how much can be forgotten when you're out of the loop for a long time!

 

[Sintra]

Volt drop = ((mV/A/m) x Ib x L) / 1000

 

[steve-irl]

Thanks again!! that's the formula I had alright jus needed confirmation of it!

now if only 5 core swa wasn't so expensive!! being quoted around €15 + VAT per metre over here for the 5 x 35s.

 

[robsparky1975]

Cant you buy from uk and get shipped over,its all standard eu colours isnt it,brown,black,grey,blue and green/yellow same voltage i think,from memory,same regs(irish version)?take it euros you are in southern ireland.

 

[steve-irl]

yep in southern ireland.. same colours, need it pretty quick tho as it's gotta go in this week.. wouldn't even know where to start to go about getting it in from uk.

 

[Knobhead]

Try this link Welcome to AEI Cables there's a useful calculator for cable runs in most situations