Air compressor Gee Whiz info

I just got my new Cambell Hausfeld 6.25HP Home Depot compressor going. After the break in (don't forget to stick an empty jack in the air chuck to release the air) I decided to do some checking to see what I really had. This says 6.25HP but we know that is a lie if it is 120v. The motor says "SPL" in the HP field but the FLA says 15A so that makes it nominally about 1HP. I hooked up my clamp on amp meter setup and cranked it up. It starts out around 12a and quickly builds to 14. <sumpin> as the pressure comes up. It is quickly cruising around 14.8- 14.9 As it approaches 80PSI the amps is 15 and around 100PSI it is 15.2 and then starts dropping off. At 150 where it makes the pressure switch it was back down to 13.9 or so. I assume this is the same phenomena as a vacuum speeding up and dropping current draw when you plug the hose. The amp readings do explain why these things don't work on a 15a. I am really curious how they get away with putting a NEMA 5-15 plug on this thing! It certainly should be a 5-20. It does recomend that this should be on a dedicated 20a circuit. I guess I am breaking out the Kliens.
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"Greg" writes:
<snip>

You definitely want a 1P-20A c'bkr & #12AWG wire for your compressor; however, the plug and receptacle are 100% rated to handle 15A all day long.
OTOH, 1 c'bkr is only rated to handle 80% of nameplate rating on a continuous basis, thus a 1P-20A device is only rated at 16A under continuous load.
HTH
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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Not really. On all cord and plug connected equipment you are limited to 80% of circuit ampacity. The plug should be sized to 125% of the equipment load.

The breaker can handle 100%, you just have to adjust the circuit ampacity for any continous load.
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From NEC 2002 210-23(A)(1) (1) Cord-and-Plug-Connected Equipment. The rating of any one cord-and-plug-connected utilization equipment shall not exceed 80 percent of the branch-circuit ampere rating.
I doubt Table Table 210.21(B)(2) will post but it says on a 15 or 20a circuit a 15a receptacle can only be used for a 12a load.
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You really need a dedicated 20a circuit. If there is only one receptacle and it serves the compressor you don't need the GFCI. I will be putting mine in tomorrow.
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Get more bang for your buck on your electrical service - do some 220 volt and convert your heavy users to 220 volt. It doesn't cost any more and you can run more tools and accessories from your 50 amp service without worrying about tripping a breaker. If you are going to air condition it, you'll be adding 220 volt anyway (assuming you do some kind of dedicated air conditioner).
Bob

and
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And while you're about it, get an estimate for a 100 amp sub with several 220 outlets. Running a big saw with crud collection when the compressor suddenly decides it's time... Might be worth it to do it all at the same time.     mahalo,     jo4hn
Bob Davis wrote:

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Greg wrote: As it approaches 80PSI the amps is 15 and around

Counter EMF. My guess is it's coming under a load that actually 'pushes back' and restricts loading.
Another thing is we would need voltage readings to know more of what was going on. If the Buss isn't pushing the needed voltage under load your amperage will be higher.
Truth is I can't bring something into the house and plug it into it's 100 amp box and expect the same performance I get from the shops 200 ampere service.
In my shop the 15 amp plug may never approach 15 amps but in the house it may not be able to run on a 15 amps because of the old voltage-amp-watt thing.
So much for practical application verses theory. Hey, it all looks good. On paper.
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Mark

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This is on one of my 20a shop circuits that are about 5' of #12 away from the 200a main. My line voltage cruises at 124 or so.
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Greg said:

And even when installing a 20 amp breaker, you may STILL kick it. DAMHIKT. You should get a high magnetic trip breaker to serve 120v motor loads, or be prepared to reset the damned thing at the most inopportune times. I have a CH '6HP' model that runs on 120V, can't be rewired for 240 (crap!), on a dedicated 20 amp circuit with 10 gauge wire about 20 feet from an 80 amp Square-D sub-panel wired #4. Kicks the breaker on startup about 15% of the time, especially when cold. The motor MFG blanked out the true HP rating with "SPEC" but the FLAs are listed as 15, same as yours. May even be the same model. A temporary solution is... never mind... I don't want to go there. <g>
Breakers higher than 20 amp are generally not 'fast trip', but generic 15 and 20 amp breakers that will be used on consumer 120v lines are. The dual pole 240v breakers are generally not 'fast trip' designs. Be prepared to order the HM breakers, as many supply houses apparently don't stock them. FWIW,
Greg G.
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wrote:

It means "I learned this the hard way"
Tim Douglass
http://www.DouglassClan.com
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I'm in Estero, I know about the heat.
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