Earlydean, using the worst case scenario of 100A is VERY unrealistic. First of all (and probably most importantly) the panel should only be loaded to 80% of its max. Secondly, even 80 continuous amps being used in a residential garage is extremely rare. In other words, the actual percentage of home garages that have a continuous load of 80A would be quite small. To wire all garages based on findings from say 0.5% of the heaviest loaded would be overkill to say the least.
I like the fact that you consider voltage drop in your calcs since far too many electricians fail to do so. However, the drop needs to be based on realistic info gathered for each specific case and not just generalizing all situations as being equal.
Delton Ebanks, the minimum size feeder allowed for that application is #3 Cu or #1 Al (remember table 310.15(B)(6) cannot be used for garages even if they are for residential use). If this is an average residential garage with a few lights and a few 120V receptacles then voltage drop should not be much of an issue. If heavier usage is expected now or in the future then you need to estimate a calculated load with which to do some voltage drop calculations. If it were my project, I would probably size the wires above the minimum since the distance involved is somewhat excessive.
BTW earlydean, are you sure that table 9 in chapter 9 can be used in this case? The heading says that table is for three-phase and I doubt that the home falls in that category.
[This message has been edited by triple (edited 02-28-2004).]
