3 phase

[boris1348]

Hi there,
i have been asked to help design an installation for a new house which is very large.
it has a 3 phase supply and i need to run some sub mains to seperate consumer units.
should i run the sub mains in 3 phase then into single phase at each of the seperate
consumer units or run single phase sub mains straight from the original 3 phase supply.
any help would be appreciated.
Boris

 

[Shakey]

Hi there,
i have been asked to help design an installation for a new house which is very large.
it has a 3 phase supply and i need to run some sub mains to seperate consumer units.
should i run the sub mains in 3 phase then into single phase at each of the seperate
consumer units or run single phase sub mains straight from the original 3 phase supply.
any help would be appreciated.
Boris

depends how far apart the CU's are

i would tend to go for single phase submains, other wise how are you going to change from three phase to single phase ?

 

[boris1348]

one mains will be 45 meters away, 2nd will be 25 meters away, the others will be roughly 15 meters from original 3 phase suplly.
there will be 6 sub mains to run in total.
would you still use single phase?
thanks.

 

[Had8Lives]

I'm amazed the electric supplier has given 3 phase supply, normally you have to prove you need it. Is there going to be any 3 phase equipment? Might be aswell to design and cost with 3 phase cable to each sub main CU and if u only end up with one phase then the 2 spare wires are there for the future. Also depends on the expected load at each CU.

 

[Shakey]

I'm amazed the electric supplier has given 3 phase supply, normally you have to prove you need it. Is there going to be any 3 phase equipment? Might be aswell to design and cost with 3 phase cable to each sub main CU and if u only end up with one phase then the 2 spare wires are there for the future. Also depends on the expected load at each CU.

But this was my earlier point, if you are using single phase CU's, how are you going to terminate the three phase?

I would just treat the three phase as three seperate phases, and run them out as single phases. Only thing to remember is warning notices if you have socket outlets in close proximity running off seperate phases (warning:400V etc)

 

[boris1348]

the expected load is going to be 20kva's at 3 of the cu's.
the other 3 will be roughly 10kva's.
there is no 3 phase equipment but anything over 25kva's for an installation the electric supplier insists on 3 phase.
thanks shakey