My calc's show a 5% VD on a 120v 20a circuit @ 75' , my ideal tester shows similar results. ALL the circuits I run when i wire a residence, save dedicated runs, are usually more than this length in total...
I would think that this is why most of us routinely install more than the minimum number of circuits required by code, and increase the conductor size when we run into the occasional circuit that is expected to be heavily loaded. This method will not produce the lowest possible installed cost, but it does allow you to sleep better, at least untill you get the service call for the 59 cent switch that failed.
#80442 - 04/15/0211:31 PMRe: The code that ate my brain
I have only seen one voltage drop problem in a residence & it was a double wide that had to have near 150 feet of 14-2 to the furthest outlet. When one of those 12 amp vacuum cleaners was plugged into it, it about choked, voltage fell to 85-90 volts.
The homeowner had hired me to find code violations so he could sue the home builder.I found a few, but couldn't help him with the voltage drop problem.
Few things are harder to put up with than the annoyance of a good example.