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1 members (Scott35),
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Joined: Oct 2002
Posts: 210
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5.5hp sounds a little big for a 20 amp circuit. You may have to carefully apply article 430 here to size your wire size, breaker size and overload protection.
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Joined: Feb 2002
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I may be wrong, but I recall reading somewhere (maybe here) that the horsepower ratings on home-use compressors and vacuum cleaners are grossly overstated.
Peter
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Joined: Nov 2000
Posts: 2,148
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CT,
You are correct, many items of this type use fictional horsepower ratings. This is the reason that Exception #3 to 430.6(A)(1) exists.
Don
[This message has been edited by resqcapt19 (edited 12-07-2002).]
Don(resqcapt19)
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Joined: Nov 2002
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Maybe a hvac type c.b might help on inrush.
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Joined: Apr 2002
Posts: 2,527
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r19don — You raise a good point. Used to be that discount stores sold $20 universal-motor circular saws that were labeled: "Develops 2¾ Horsepower." Kinda’ like the scam audio-amplifier “power-rating” abuse ~25 years ago in the US that required government intervention. Based on the numbers on many portable-compressor labels, either the street lights within a mile radius should extinguish, or the motor is so efficient it should make the watthour meter turn backwards—I’m not sure which.
On the subject equipment, until some basic electrical measurements are done, the problem could stem from one or more of several typically found in the troubleshooting process.
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Joined: Apr 2002
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Based on 99NEC table 430-148, a 5hp 1ø 115V motor is about a 56-ampere running load or FLC. Also, a ¾hp 1ø 115V is rated ~14 amperes. That magic “5.5hp” motor is so wonderful that it should or make the building watthour meter turn backwards, or dim street lights for a mile radius—possibly both. Maybe it’s time to revise some of the laws of physics.
[This message has been edited by Bjarney (edited 12-07-2002).]
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Joined: Jan 2002
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5.0 HP compressors found at Grainger.com show an amp rating in the neighborhood of 22 amps. Sounds like you have to upgrade the service.
I know this is not your exact brand, but like equipment should run alike.
FYI, you would also have to upgrade the wire and probably the conduit. I will let the real electricians on this board help you with that.
Scott
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Joined: Apr 2002
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Heed Don's comment.
430.6(A)(1) Exception No. 3 makes it quite clear that the nameplate amps is used to determine the ampacity for a motor operated appliance.
Remember to look at 430.22 although doubt that many appliances are considered 'continuous' duty.
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Joined: Jul 2002
Posts: 175
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INTP,
Is it possible or practical for you to measure the current that this motor draws?
You wrote - "It just says 115V/60Hz/1PH/15A"
This indicates that the nameplate Full Load Amps(FLA) rating is 15 amps.
If the actual current drawn is not more than the nameplate rating, there doesn't appear to be anything wrong with this installation except that the circuit breaker is under-rated.
Unless you require the compressor to be portable, it could be hard-wired (no receptacle) and use a 30 amp breaker.
Ed
[This message has been edited by electric-ed (edited 12-07-2002).]
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Joined: Dec 2002
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Sounds to me like you got a short
what type of cord is run to it?
Is it stranded frayed at connector or inside the termination box?
the little strands can short than clear making trouble shooting difficult
Does the motor have a capacitor?
If so have it checked or look for shorts make sure covers are not pinching wires
Make sure you disconnect power before doing any work and capacitor will still hold a charge after power
Is disconnected
Brotherhood of the 9.3X62
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