Power mains question: wire gauge

Air compressor 1/2 hp motor rated 220v (2-wire, not 3-phase) @ 15A. Distance from load panel ~100 ft (as the conduit runs).
15A can be handled by 14 gauge, but I'd normally go with 12 gauge due to start current.
With such a distance, is it recommend to up-scale the wire to 10 ga?
Thanks.
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DaveC wrote:

I would, since the starting current is much higher.
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"DaveC"
** Giant HUH ??
Such a motor normally draws around 3 amps.
... Phil
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Phil Allison wrote:

Up to 4.9 Amps, according to the 2011 NEC (Table 430.248). And that's all you have to provide in terms of feeder/branch circuit ampacity.
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On 29/12/2012 9:51 AM, Paul Hovnanian P.E. wrote:

Hmmmm, did the OP leave off a 1 or has he a very inefficient 1/2 hp motor ??
Rheilly P
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On Fri, 28 Dec 2012 17:51:18 -0800, "Paul Hovnanian P.E."

As another poster stated, 220V @ 15A is like 4.5 HP (Or VERY lossy)
Something is amiss somewhere.
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Hmm, now that you mention it...
Lemme check my notes.
[OP]
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3.1 horsepower.
Thanks.
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The rating plate on the compressor says 3.1 hp, 15A, 230V.
Yet I see that 3 hp @ 230v is 18A:
<http://www.cordellmfg.com/tech_fulload.htm
Won't the 14 ga. wire and 15A breaker be taxed?
Should I reconsider the 14 ga (upscale it to at least 12?) wire for this compressor?
Thanks.
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Yet your original post said 1/2HP. Make up your mind.

That's high. 3HP is about 2.2kW, or 7A at 240V. Double it (motors aren't 100% efficient) and it's in the 15A area.

Yes. Use a 20A breaker and 12GA.

Go figure that you'd expect a different answer with a different question.
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OK you go by the nameplate rating. the conductor is sized to 125% of that. (you get 18.75a) The minimum wire size using 310.16 is 14ga. You can oversize the breaker to 250% of FLA so you could use a 37.5a breaker, that rounds up to 40a. per table 430.52 and 240.4(B).
Voltage drop is a separate issue 14ga wire with a 15a load 100 feet out drops 9.48v or about 4% of 240v. That is probably a little more than you want (more than the FPN recommendation). If you go up to 12ga you drop 5.9v (2.5%) so that is probably what I would do. You also will usually be fine with a smaller breaker than the max in 430.52 but there is a chance a 20a might nuisance trip.
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Paul Hovnanian P.E. wrote:

Maybe OP dropped a leading '1'. A 1.5 HP 230V 1ph motor still only draws up to 10 Amps per the NEC.
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On Fri, 28 Dec 2012 17:51:18 -0800, "Paul Hovnanian P.E."

all

I am not sure where, but look up motor start loads and regulation. It may not be precisely discussed in NEC but for many motors droop during start is an issue, and a 100' run can have an excess of that. The sizing issue is about start conditions as well as run conditions.
?-)
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#12 is 1.6 mohms/foot. That's 0.32 ohms total. The short-circuit current from 220 volts is almost 700 amps. A half horse is only around 400 watts, about 2 amps. I'd use #14.
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John Larkin wrote:

Until the motor or compressor is replaced with a larger unit. Then all bets are off. It's cheaper to do it right the first time. You could even put a small breaker box by the compressor & run AWG 6 to it, to power other tools, as needed without starting from scratch.
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That's a good idea. I'll talk it over with the owner.
But for now I want to settle on what size conductor to use if it's just to supply this one compressor.
Thanks.
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On 12/29/2012 3:05 PM, DaveC wrote:

100 feet of AWG 6 will set you back some C-notes. That's an expensive investment if you don't need it.
Rick
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On Sun, 30 Dec 2012 01:28:08 -0500, the renowned rickman

It's also a sweaty PITA to pull.. ( I ran some to a manly (for single phase) compressor and kiln).
Best regards, Spehro Pefhany
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rickman wrote:

The suggestion was to put in a sub panel, if there is a likelyhood of more tools that require 240.
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On Sun, 30 Dec 2012 18:26:04 -0500, "Michael A. Terrell"

...and it's almost always cheaper and easier to run tools separately from the main with more common, and *far* less expensive, #14 or #12.
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