voltage drop

[atlas electric]

I have a voltage drop question. I have a connected load of 200amps and a distance of 385 feet using copper conductors. This is a single phase system. Is it as it appears that I will have to use 500mcm copper conductors? Thank you.
John

 

[bphgravity]

Re: voltage drop

What calculation are you using? What is the system voltage, and what percent drop are you allowing?


I use cm= 2 x k x d x i / vd permitted

cm= 2 x 12.9 x 385 x 200 / 7.2 = 300kcmil

I am using a K of 12.9, vd of 3% at 240-volts.

If this is a service, and no voltage drop is expected on the feeder or branch-circuit end, you could raise the vd to 5% and still be okay.

 

[iwire]

Re: voltage drop

With 200 amp load on a 240 volt service 385 feet long I come up with 300kcmil to stay less than 3% drop or 3/0 AWG to stay less than 5% drop.

Same as Bryan arrived at using his head.

I arrived at this the lazy way , from the voltage drop calculater that is available at Mike Holts "Free Stuff" page.

[ April 19, 2003, 11:33 AM: Message edited by: iwire ]

 

[bennie]

Re: voltage drop

What is the calculated load?

 

[darren]

Re: voltage drop

VD = (2x(KxQ)xIxD)/CM

As per Chapter 9, Table 9
Conductor Size 300kcml
Number of Conductors 2.00
Distance, from supply 385.00
I, Amperes/Current 200.00

K=Direct Current Constant
CU 12.90 (used)
AL 21.20
Q=Alternating Current Adjustment Factor 1.05 (eddy currents) 2/0 and larger. Divide Table 9/Table 8. Example (0.045 / 0.0429)

CM=Circular Mils 300,000.00 Chapter 9, Table 8.

Voltage Drop = 6.95

Serving Voltage 240.00
EVD (Resulting VD) 233.05
VD % 2.89%

WHEW! So I come up with volts drop/loss of almost 7 which would be just under 3%VD. Hope this helps.

 

[atlas electric]

Re: voltage drop

Thank you everyone for your time and effort on this problem. You were all very helpful.
John

 

[bennie]

Re: voltage drop

John: You wrote "200 amp connected load". The calculated load will be considerably less.

When cost is a factor, using the connected load is a bit of overkill.