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View Full Version : Do I use the calculated load or the main breaker rating to determine voltage drop and


karmelcopia
Apr 22, 2010, 12:22 PM
I am running a feeder to a panel in my outbuilding. Do I use my calculated load or do I use the 100 amp main breaker rating for my voltage drop and feeder sizing calculations?

Missouri Bound
Apr 22, 2010, 12:39 PM
The voltage drop calculation is determined by wire size and length of run. How far are you going?

karmelcopia
Apr 22, 2010, 01:01 PM
I am running nearly 190 feet to the outbuilding. Planning on a 100 amp double pole main breaker although the calculated load is significantly less.

karmelcopia
Apr 22, 2010, 01:07 PM
Do I have to gauge my wire on the calculated load or the 100 breaker rating ,as well as figuring in the voltage drop?

KISS
Apr 22, 2010, 04:03 PM
Base your calc's on the feeder breaker.

As an example, you are allowed a 60 A feeder and a 100 A subpanel main in your outbuilding . That 100A breaker will act as a disconnect.

The wire size is based on the feeder breaker size and distance.

Missouri Bound
Apr 22, 2010, 05:34 PM
Karmalcopia, as Kiss said...
Here's a calculator you can use if you like.
Wire Size Calculator (http://www.csgnetwork.com/wiresizecalc.html)