please check my numbers

[pgordon]

A residential service calculation.
1200 amp 3 phase 4 wire 480/277v 300' long ,75C thhn cu conductors installed in pvc. 3 sets of parallels, 4 sets of parallels.
I come up with 4 sets of 350 mcm good for 300'
I come up with 3 sets of 600 mcm good for 300'
The engineers say 4 set of 600 mcm.
I think this is over kill.

 

[iwire]

A residential service calculation.
1200 amp 3 phase 4 wire 480/277v 300' long ,75C thhn cu conductors installed in pvc. 3 sets of parallels, 4 sets of parallels.
I come up with 4 sets of 350 mcm good for 300'
I come up with 3 sets of 600 mcm good for 300'
The engineers say 4 set of 600 mcm.
I think this is over kill.

Code wise 3 sets of 600 will do it.

If the EEs want 4 sets of 600 then by all means provide it, install it, charge for it and enjoy the extra money you just made.

I have run five sets of 500 kcmil for a 1600 amp feeder that was only 200' long but it was what the EE wanted so that was all that mattered.

 

[ultramegabob]

this is going in a residence?

 

[pgordon]

iwire, good point . I will do just that.
ultramegabob, Yes a this is a BIG house , 45,000 sq,

 

[iwire]

Yes a this is a BIG house , 45,000 sq,

In that case they can afford the extra copper.

The real shame here is the NEC load calcs have already increased the size of the service much larger then it needs to be.

 

[masterinbama]

I would definitely like to get the extra profit and overhead on 1200' of 600 mcm. It would make that bottom line much better.

 

[normbac]

out of curiosity if you dont mind what is the ball park of an electrical bid for a house that big

 

[JWCELECTRIC]

A residential service calculation.
1200 amp 3 phase 4 wire 480/277v 300' long ,75C thhn cu conductors installed in pvc. 3 sets of parallels, 4 sets of parallels.
I come up with 4 sets of 350 mcm good for 300'
I come up with 3 sets of 600 mcm good for 300'
The engineers say 4 set of 600 mcm.
I think this is over kill.

Why not 3-Phase,4W 208/120 - Then you don't need a step down transformer with the loses running constantly?

 

[iwire]

Why not 3-Phase,4W 208/120 - Then you don't need a step down transformer with the loses running constantly?

Well then you would need a 2,400 amp service and maybe 8 sets of 600 kcmil.