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3 HP on a 15 Amp 120 v circuit #5286498 12/05/19 09:53 PM
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Snagglefoot Offline OP
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This Makita Air compressor is labeled 3 HP but has a 120 V 3 prong cord. I’m used to the limit being 2.4 HP on a 15 Amp breaker. (120 V x 15 A)/746 Watts per HP. Does anyone know the answer on how Makita expects this to be run on a 120 V outlet.I suppose one option is to upgrade to a 20 A breaker if the wiring is up to it. A search of the internet brought up a fellow asking the same question about the same compressor.

E13176B7-BFF8-4996-BE4F-C3BE10478363.jpegF9D5A709-73B2-4DAD-9C03-82E7680CBCDD.jpeg

If you want the job done right......do it yourself.
Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286503 12/05/19 09:59 PM
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Donald Online Content
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I would get a AC peak hold amp meter. Maybe they did some marketing rounding of the HP.


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Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286510 12/05/19 10:11 PM
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Rand Offline
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peak hp its how shop vacs are 6.5hp.

that air compressor draws around 13.8amps. so its really more like 2 continuous hp.



ps those are great air compressors.. none better in that size.


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Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286511 12/05/19 10:12 PM
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Snagglefoot Offline OP
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Just found the spec sheet on the net. It’s 2.1 running horsepower and 3 peak HP. Problem solved. Looks like a bit of false advertising. Thanks.

spank

Last edited by Snagglefoot; 12/05/19 10:15 PM.

If you want the job done right......do it yourself.
Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286519 12/05/19 10:26 PM
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P10crew Online Content
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Snag it’s the new math. Smoke and mirrors

746 Watts per hp and don’t forget to add the service factor. Modern motors are usually 1.15 sfa the good old ones were 1.25 sfa.

Last edited by P10crew; 12/05/19 10:32 PM.
Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286643 12/06/19 06:57 AM
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edwardh1 Offline
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like toilet paper and paper towels, 6 of their rolls equal 400 of other brand.


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Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286665 12/06/19 07:52 AM
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Dave Sherman Offline
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There was a bit in the news years ago about air compressors having misleading or meaningless HP ratings, namely against Craftsman and CH. Their cryptic rating was based on the instantaneous power it could deliver for a split second from the inertia of the rotating assembly if it suddenly stopped. Totally meaningless for an air compressor, but I'm sure the marketers thought it was a great idea. I have a "3 HP" Craftsman that was rated at 13 amps at 120 volts. Yeah, sure. Thought it was funny when years after I bought it, it was recalled for a possible fire hazard, and when it came back from repair it had a new sticker on the motor shroud that says 1.5 HP. Guess they decided they had to come clean and state that it's not really a 3 horsepower motor.


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Re: 3 HP on a 15 Amp 120 v circuit [Re: Snagglefoot] #5286720 12/06/19 09:17 AM
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bullwinkle Online Confused
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Their horses aren’t Clydesdales, more like Shetland ponies! You should be OK, but a stout extension cord & running on a circuit with nothing else will be necessary for 15A 120V.


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Re: 3 HP on a 15 Amp 120 v circuit [Re: P10crew] #5286785 12/06/19 10:39 AM
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Originally Posted by P10crew
Snag it’s the new math. Smoke and mirrors
746 Watts per hp and don’t forget to add the service factor. ...
... And that's per horsepower electrical input power. Mechanical output power will be substantially less, because the motor is not 100% efficient.


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