Voltage drop in service entrance wire

[fastline12]

I was recently talking with a design tech and we were comparing Vdrop data and his calculations were quite different from mine. I asked him how his were calculated and he said he was just using a PC based calc that someone gave him. Not saying his are wrong but I would really like to figure out where the discrepancy is.

Someone here willing to post a formula along with referenced data for the calculations?

 

[waross]

Ohm's law, not just a good idea, it's the law.
But R is not just R, it is actually Z for voltage drop. The X:R ratio of Z may be significant and the phase angle of the I may be significant.
How about you post your formula?

Bill
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"Why not the best?"
Jimmy Carter

 

[fastline12]

Well, that is sort of where I am at in the calculation. I am thinking that some of these calcs have an engineered margin for PF of about .8-.9 which would certainly throw things. All calcs would be at 60hz. I will dig up my forumla to see if it gels. I think I worked it from the EE law side rather than the NEC code book side which might be where the issue is. I am not as concerned of the NEC data as much as I am concerned that I have done the correct calculation and accounted for all present conditions.

 

[starkopete]

Hi,
This is the NEC.

http://www.dolphins-software.com/IEEE_ExactFormulae.htm

Thanks

 

[fastline12]

That is precisely what I was looking for. Thanks a bunch!