George,

Your description of "runs just fine" is not quite an accurate appraisal. In
fact it is quite vague. Just because a motor runs doesn't mean that it is
wired correctly or safely. "Runs just fine" doesn't imply what load is
imposed on the motor. Phrases, like "fully loaded", "2%", "1%",
"efficiency", etc. have exact meanings more or less as they are used to
describe conditions of operation. Before you poo-poo Grant's chart or any
other published standards, you are going to have to come up with a better
argument, than "runs just fine".

Bob Swinney
"George E. Cawthon" wrote in message
...


Ted Edwards wrote:

Bob Swinney wrote:

Charts of this type giving motor hp or motor kva instead of amps are
usu.
based on the amount of current a motor would "draw" if working fully
loaded.

Perhaps Grant's chart is based on starting current which is typically
quite a bit higher than run current, even at full load. While to brief
in proper operation to overheat the wires, I have seen a case where a
small generator could keep an appliance running but couldn't start it.

Ted

The chart says it is from Dayton Electric Co., so I guess
some one could ask them. Based on just the figures given
for 1 hp and under single phase 115V, we know it isn't for
2% voltage drop. And it isn't based on inefficient motors,
reasonable starting currents, and practical knowledge, based
on other published data and experience. For example, 1/8 hp
motors don't require 14 gauge wire, they run just fine on 16
gage and even 18 gauge wire. They even run just fine on 14
gauge extension cords that are 200 feet long.

Another example is my compressor is rated at 5 hp, but we
know that is a lie and is probably close to 1 hp. It runs
just fine from a building that is supplied by about 100 feet
of 10 gauge wire. That is in stark contrast to the chart
that indicates 4 gauge wire would be required for a 1 hp
motor.