Voltage between phases (3Ph supply)

[AngloSaxon]

I'm sure the question I'm about to ask has a very simple answer, yet it's one that I'm not aware of!

When designing circuits from a 3-phase dis bd. why are single phase loads separated between rooms/areas? I understand there is a p.d. between the line conductors of 400V, but why must they be spatially separate?

For example, I have a TP+N dis. bd. where I am supplying a number of single phase ring circuits. I am aware that I shouldn't mix phases within rooms, but I am unsure as to why. Could someone please enlighten me?

Thanks in advance!

 

[darai]

Think about load balancing and all it implies.. very important