Voltage Drop Calcs.

[steveve1]

Often times we, as contractors, are given "engineered drawings", indicating loads a great distance from their source. The drawings do not indicate wire size to accomidate for voltage drop. As the installing contractor, we must insure that the proper wire size and necessary conduit size is installed. Generaly I use Table 9 with note 2 (NEC 1999) to compute line loss. But what of single phase (208v/240v) and three phase loads? Is a different calc. used?

 

[ralpha494]

Re: Voltage Drop Calcs.

I was just looking at various formulas yesterday to transfer to the 2005 code book. Voltage drop didn't have 1.73 in it. I like using the voltage drop calculators at www.electrician.com. I'll go there and double check later.

 

[charlie b]

Re: Voltage Drop Calcs.

A single phase calculation will have a factor of "2" built into the equation (for two times the length of the run). A similar three phase calculation will have a factor of "1.732" (i.e., the square root of 3) built into the equation, in place of the factor of "2."