My new edge sander was delivered today, Grizzly 6x80. In the version
of the manual on the website they list it as 1.5 HP 16A/8A. But in
the manual that came with it and on the nameplate on the motor it says
1.5 HP 20A/10A.
Now I should probably run a dedicated 220V line to it regardless, but
for the time being I thought I was going to be fine on my 20A 110V
circuit. I just think it's very weird because if it's really drawing
20A then why are they calling it 1.5 HP? 20A should give 2 HP. I was
under the impression that they couldn't lie about the amps, but HP
ratings were more fudge-able. It's a 1725 RPM motor, and looking at
the motors Grizzly has in their catalog the 1.5 HP 1725RPM model draws
17A, whereas the 3450RPM draws 15.6. So I suppose that can explain a
bit of why the number is higher than I expect, but not all of it.
Have they just found a new source of really inefficient motors?
I wired it for 110 and it ran fine with no belt on it, but that
doesn't really mean anything. I need to build a stand for it and get
it up on that before I start bolting on all the tables and whatnot so
it's going to be a while before I can test it under load.
I think that's a bit optimistic. Baldor's "premium efficiency" 3HP
motor gives 85% efficiency and 96% power factor.
Their more typical 3HP motor gives 78% efficiency and 85% power factor
for a total efficiency of around 66%.
er... isn't the starting current somewhat higher than the running current -
(Back EMF and such?)
What's your fuse rating? If it's a slo-blo spec that would usually indicate
that a startup surge is expected and it will draw considerably more juice at
switch-on than when performing. In this case you can't relate ampage to
Is this what we're talking abiut, or have I missed the point?
(Sorry, I'm not really familiar with 110 v stuff 'cos we don't have it here
Horsepower ratings aren't always all that precise, and motor efficiency
can lead to higher max draw.
I suspect it's simply an inefficient motor. Also, it's likely that the
motor will hardly ever actually draw the rated amount. Most shop tools
(except for dust collectors) aren't running anywhere near full load.
But marketing departments making specs sound as good as they can is
right up there with death and taxes. The Sawstop contractor saw
actually says 1-3/4 HP which I've never seen anything say.
I found this link which says the minimum efficiency for a NEMA "Design
B" should be 79%. I don't know what a Design B is.
Even at 75%, 20A at 115V is well over 2 HP. Or going the other way,
1.5 HP at 75% is 13A, which is exactly what my table saw says.
The manual actually has a page where it says the machine will draw 10A
on 220V under normal use. Which doesn't make any sense, but that's
what it says.
Before adding special circuits I would first plug it in to what you have and
try it out during actual use.
On a 15 amp circuit I run a radio, lighting, 12 amp dust collector and a 15
amp router, no problem at all unless the compressor comes on. typically
your heaviest amp draw is going to be when you start the machine, usually
you don't work on the machine until it comes up to speed and the amp demand
Watts=volts x amps. 1HP t6Watts. Double the voltage then half the amps. It
is 240 volts and 120volts in residential. 110volts and 220 volts went the
way of the Doh-doh bird long ago. Using old numbers with newer equipment
will do funny things to your mathematical calculations compared to real
That's definitely what I'm doing, and I built the base for it and got
it setup. Seems to run fine. The one set of 4 ft lights on the same
circuit barely flicker when it starts up. It starts up fine with the
spindle sander next to it running too, but that's just rated at 2.5
amps. Still, if the manual is to be believed that should have brought
upon the end of the world. The dehumidifier is also on that circuit,
but we're getting to the end of the season where it's needed. Before
you know it I will be freezing my ass off in there again.
I can say that a TS and a space heater on a 20 amp circuit is a no
go :) Well, it's a go.. to the panel to reset the breaker.
Anyway, I raised the topic not so much in regards to what I need to do
to make it work, I can deal with that. It was more that I have
definitely heard on the wreck that you can't trust the hp rating, but
the amps were more reliable because that gets tested by UL. And I
just wonder if the marketing departments haven't figured that out and
now you can't trust anything.
Might I also add that there isa 20" fan blowing on my circuit also.
A space heater tends to use a constant higher amp so they will tend to use
most of the amps that they are rated at.. Electric motors tend to use more
amps getting up to speed than they do during actual usage.
UL tests that the amps don't ever go higher than the nameplate. They
don't test whether they go as high as the nameplate.
I've heard a few stories of drill/jigsaw/etc manufacturers padding the
amperage rating to make the tool seem more powerful. No evidence that
it actually happened, but it sounds like something someone would do...
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