Main Feed for 3 phase unit. What size cable would be best?

[mgnelec09]

I went looking at a job yesterday.

It is going to be a commercial office block with 3 large offices with around 25 d/sockets in each.

There is a large sub main in an adjacent building about 40 metres away.

It is all going to separately metered .

I am just aking your opinions on what size supply cable would be suitable to run from the sub main to the building which will be supplying 3 x 100amp single phase consumer units.

any suggestions?

 

[telectrix]

25mm will give you 100A/phase. whether you want to go larger to allow for increase in demand is your call. have to do a volt drop calc. should be OK at 40m.

 

[telectrix]

top of me 'ed abvout 8volts at 100A,40m.

 

[mgnelec09]

Thanks, think the actual length is about 33m but say 40 to be sure.

 

[telectrix]

do your vd calc. at 100A , 40m. my figure of 8v is a guesstimate.

 

[netblindpaul]

All above sounds good, but it may not be the 25 dso's that are your main load to consider, though @ 100A you should be fine I suspect.

 

[Steve1412]

Lighting and heating to consider...you need more info and proper elec spec me thinks.