I was in Harbor Freight in Columbus, OH the other day and saw they are
having a huge sale on November 28 -- the day after Thanksgiving. This
is chain-wide and you can access all their locations by going to
I am sure they will have some GREAT deals!
I went to my first HF yesterday. They had a marvelous 2hp motor for my
table saw that only drew 15a and weighed about the same as most 1hp motors.
How on earth do they do that, and for only $60!? I can't wait to install
Most of the rest of the stuff there was junk. I would have been
disappointed, except for the motor.
BALONEY! 1HP is 745.7 watts. That's a little over SIX amps at 120V.
2HP, 1491.4 watts, equates to a current draw of approximately 12.42 A at 120V.
15A draw, at 120v, *WILL* give 2HP at the motor shaft, if the motor has an
efficiency factor of roughly 83%.
With motors in that size range typically having efficiencies of 80-85%,
there is *nothing* unreasonable about the rating. It looks like an -honest-
Unlike my little shop-vac, which claims "3.0 HP (peak)", and for which
the 'plate' reads 7.25A, 115VAC. To deliver 3HP at that voltage/current,
the motor would have to be 268.3% efficient. *snort*
Anyway, for rough figuring, electrical equates for 1HP, at typical (80-85%)
7-1/2A @ 120V
3-3/4A @ 240V
4-1/3A @ 208V (2-phases from a 3-phase 240V distribution)
I would like to see the motors you descibe!
Graingers lists a high efficiancy 1-1/2 HP motor that draws 14 amps @ 120
volt, 7 amps @ 240 volt. Standard efficiancy motors run higher amps yet. A 2
HP high efficiancy motor is shown to run about 20 amps @ 240 volts. Again
standard efficiancy motors are higher amps yet.
The most you can run on a 20 amp, 120 volt circuit is a 1-1/2 HP motor. @ HP
goes to 240 volt.
I have always used 1 HP per 10 amps for 120 volt, 5 amps per HP for 240
volt, it my run SLIGHTLY less with higher horsepower motors, but you will be
I'm well aware of the math, and you're right about that. The problem is that
your "real-world" figures are what's BALONEY! I've never seen any induction
motor on this planet with from a reputable maker with a usable service rating
that comes anywhere close to those figures. What you're likely to find for
actual induction motors:
1/3HP motors would draw around 4-6A, 1/2HP from 7-9, 1HP in the 13-16 range,
and a 1.5HP motor 18-22. All of this is pretty close for both split-phase and
cap start. I don't have cap run figures on hand.
Go and look at products from a real motor company.
I'm not arguing your figures, because I have an old 1/4 hp
that say 5.4 amps, but 16a at 120v for 1 horsepower means an
efficiency of 39 percent. Is this true of even modern
My Baldor 1/4 hp (about 1 year old) rated at 2.8 amps which
comes to 56 percent efficiency and I have a 1 hp (about 30
years old) rated at 12.2 amps which is 51 percent. All of
this seem rather poor considering the efficiency of
Like I said in my post, 1HP would be in the 13-16 range. The 16, of course, is
way up there and not seen much any more, and your12.2 is pretty close to 13. I
can just mention general guidelines, since I haven't looked at every motor or
spec sheet out there. The 1HP motors I have on hand are 14.7 or something like
The 1/4 HP at 2.8A really suprises me for an induction motor, although I don't
doubt the rating if it's from Baldor.
Does Baldour count as a 'reputable' manufacturer, and a 'real' motor company?
How about one of their units, rated for continuous use, i.e., 100% duty cycle
at full load?
it's 120/240 convertible.
The plate says:
1.5HP at 120V, 2.0 HP at 240V
12.8 A at 120, 8.6 A at 240.
At 120V, "theoretical" for 1.5 HP is a tad over 9 A,
figuring 83% efficiency takes it to about 11-1/4.
It's gonna be 19-22A at 120V, you say?
Seems like _this_ 'real world motor', from a 'reputable manufacturer', is
a lot closer to my numbers than yours.
Hell, I've got engineering reference handbooks (from 'inconsequential'
technical publishers like McGraw-Hill) from the *1920s* that document
"average" efficiencies for 2HP 220V motors at 82% at 1/2 load to 84% at
At 10HP, they're 85% efficient across the range.
At 100HP, one is looking at 91% efficiency at 1/2 load, and 92+% at full load.
I will note that starting current, _for_full_load_torque_, is stated to be
2.7 - 3 times the full-load current.
Your claimed 19A @ 120V giving 1.5 HP equates to a _maximum_ 'efficiency'
of 49.02% The 22A 'high-side' is even worse -- 42.34%.
This implies that "modern" motors are significantly less than 2/3 as efficient
as the 'typical' motor built in the 1920s.
Somehow I *really* doubt that that is true.
As one gets down into the fractional HP range, overall efficiencies do tend
to go down significantly. I've got a FASCO INDUSTRIES 0.1 HP (honest
measure, I've had it on a dynamo), that draws 1.08A at full load. So says
the plate -- I measured 1.05 A, using a _non-calibrated_ meter. (a 10% error
wouldn't surprise me.)
At a straight scale-up to 1.5 HP, that'd be about a 15.5A draw.
Great deals on JUNK, just kidding some of there stuff is ok if your like me
just a hacker, what I dont like is the idea that everything and it's not only
Harbor it's Home depot Menards Lowes etc that most think's today is either
made in China or Tiwan Korea etc.
Do we make anything here in the good old USA any more
Small world. I'm actually sitting here in Zhongshan, China as I'm typing this.
I'm at a factory where about 3000 workers are enjoying the jobs that used to
be in the USA. They used to be minimum wage jobs in the USA that became too
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