voltage drop

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peter d

Senior Member
Location
New England
Re: voltage drop

Your question cannot be answered unless we know the calculated load.

Also, are you planning to use copper or aluminum wire?
 

sky1

Member
Re: voltage drop

"IF" your load is a full 200 amps and this is a feeder, the NEC recommends a maximum voltage drop of 3%.
3% of 240V is 7.2V
The formula for calculating voltage drop for single phase is:
Circular Mills =2kxLxI/Vd
k=12.9 for copper @75 c
L=length
I=current
Vd=Voltage drop
You would need a conductor with a minimum of 200,667 circular mills = 4/0
For three phase subsitute 1.73 for 2 in the above formula.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: voltage drop

A 200 amp panel will seldom have 200 amps worth of load running on it. You can certainly design it to have no more than 3% VD with a load of 200 amps. But if you do, you may end up with a larger feeder than is needed. That is a design (and economic) choice, not a code issue. But then, VD is not a code issue either.

I agree with sky1's calculation of a 4/0. But if the load were actually, let us say, 160 amps, then a 3/0 would be adequate.
 
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