Excuse me! Runs just fine doesn't me just runs; you could
accurately assume that runs just fine means it runs as
intended with no problems. Runs just fine also means that
the motor runs within the temperature intended. But, excuse
me, next time I run my compressor I'll measure the voltage,
will that tell you anymore about how my motor is running?
How the hell would I measure the load on the compressor
motor. The load is the compressor, if the load is 90, 80,
or 70 percent of capacity, what do I care, that's determined
by the manufacture. You think they reduced profits by
installing a motor that runs at 50 percent capacity?

There is no safety issue, if the load is too much for the
circuit, the breaker will trip and protect the wire, if the
motor get too hot, the internal fuse or break will switch it
off and protect the motor.

I didn't poo-poo the chart, for all I know it is correct for
its intended purpose. What I did was dispute some of the
possible bases for the chart. If you can't figure out that
a 1 hp motor won't run fine on 10 gage wire when 4 gage is
require, then you shouldn't bother with replies.

It's funny that you didn't offer any real information or
insight.

Bob Swinney wrote:

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.