sizing neutral on a split phase 180 deg

[vde-electrician]

Hi, looking at installing a sub main down to a field to supply caravan hook up points. the supplier has stated they are installing 2 x 100 amp split phase 180 degrees apart. not worked on 460v/480v split phase - my question is how do i go about sizing the neutral. i plan to run a steel wire armoured. i plan to export the 2 phases down the field. does the neutral need to carry both maximum currents, or do the phases effectively cancel each other out requiring a smaller neutral conductor? any help or where to look for guidance is kindly appreciated.

 

[bill01803]

What do you think the neutral current would be with a balanced load?

 

[vde-electrician]

What do you think the neutral current would be with a balanced load?

hi bill
my initial thoughts are that it would be the same as a 3 phase supply 120 degree apart. that the neutral would be equal size to one of the line conductors? would you agree

 

[pc1966]

The situation is a bit like 3-phase neutral, in that a linear and balanced set of loads lead to zero neutral current, but worst case of full load on only one of the line-neutral sides could lead to the neutral carrying the same current as the supply rating.

Of course reality is likely to be somewhere between the two and it might be possible to use a half-side neutral, but without detailed knowledge of it, and if the cable is not huge singles, then you are probably going to end up using 3-core SWA, or 4-core if a copper CPC is needed for ADS or PME-bonding requirements, so neutral will be the same anyway.