SawStop vs. ShopFox HP ratings

[Christopher Charles]

Hi all,

Riddle me this. I recently found a SawStop PCS 1.75 HP used for a nice price. I have 220 in my shop and confirmed that I can upgrade to 3 HP, figuring I could use the 1.75 HP motor in my 2 HP Shop Fox dust collector. The dust collector motor has been making bearing noise when it's cold out for a while and I figure its days are numbered....and I could upgrade, fix the DC issue and still be way ahead cash-wise.

Here's the quandary: I checked the plates on both motors. The "2 HP" Shop Fox says it is 12 A at 220 = 6 A / HP. The 1.75 SS motor says it is 7A at 220 = 4 A / HP. Does this mean the SS motor is really 33% more efficient?

Best,
Chris

[Charles Coolidge]

1HP at 220vac at 90% efficiency = 4.19 amps.

[Frank Pratt]

Hi all,

Riddle me this. I recently found a SawStop PCS 1.75 HP used for a nice price. I have 220 in my shop and confirmed that I can upgrade to 3 HP, figuring I could use the 1.75 HP motor in my 2 HP Shop Fox dust collector. The dust collector motor has been making bearing noise when it's cold out for a while and I figure its days are numbered....and I could upgrade, fix the DC issue and still be way ahead cash-wise.

Here's the quandary: I checked the plates on both motors. The "2 HP" Shop Fox says it is 12 A at 220 = 6 A / HP. The 1.75 SS motor says it is 7A at 220 = 4 A / HP. Does this mean the SS motor is really 33% more efficient?

Best,
Chris

Yes, the difference is partly due to greater inefficiency of the Shop Fox motor. The cheapest induction motors can be very inefficient.

I should add that it isn't all due to inefficiency. A large part of the difference could be due to the cheap motor having a much lower power factor, which raises the current draw while not actually using more power. It's because of the current being out of phase with the voltage.

[Christopher Charles]

Thanks gentlemen. Maybe those horsepower ratings are actually useful in some cases--I've paid more attention to amps and wattage in the past given the wild claims of hp by some manufacturers.

[Frank Pratt]

Thanks gentlemen. Maybe those horsepower ratings are actually useful in some cases--I've paid more attention to amps and wattage in the past given the wild claims of hp by some manufacturers.

It's the universal motor HP ratings (the kind with brushes) that you have to ignore because they are a lie & completely meaningless. Like the 6.5 HP shop vacs that might ​actually be 1 HP.