Buying a used air compressor: tips?

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bud-- wrote:

Bullshit. I never stated that I had a 3HP motor.
I did state that I had a compressor with a 15A motor, and that it was a "3HP SPL" rated motor.
At no time did I claim that I had a 3HP motor.
Nice troll, though, as with the other trolls in this group. You guys had me going for a bit, shame on me for falling for it.
Jon
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On Thu, 10 Feb 2011 12:46:22 -0800, "Jon Danniken"

It ain't 2.3HP, either.

It's unseemly to pat yourself on the back in a public forum.

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On Wed, 09 Feb 2011 17:37:13 -0500, snipped-for-privacy@snyder.on.ca wrote:

Nice explanation. Might be able to use it when I buy a compressor. Want a cast iron, as heavy duty as possible on 120V, 15 amp. Light use for impact wrenches, filling tires, etc. The garage circuit also carries 6 2-tube 4' fluorescents. Don't want to be running to the basement because of the breaker tripping. Any way to spec a 120V compressor motor for this? Stay under 15 amps? 13? I could pull a 220V service to the garage if I had to. I'd get an electrician for that. I stay away from electricity.. Don't want to if not really necessary though, because the 1/2" condiuit is 50 years old and runs under fairly new and good sidewalk. That might cause issues.
--Vic
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On Wed, 09 Feb 2011 19:51:57 -0600, Vic Smith

I just switched mine over to 220 - now I can start it when it is cold. It is rated at 14 amps on 120, and 7 on 220, but it was popping 15 amp fuses on a normal startup, and 20s if it was at all cold.
On 220 the 15s start it when cold.
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On Thu, 10 Feb 2011 08:47:10 -0500, "Stormin Mormon"

Thanks for that advice. Pretty much settled on this. Should be all I'll need. http://www.autobodytoolmart.com/pdf/8845Brochure.pdf
Sears has had it for $449 so I'll wait for that. Not ready to pull the trigger anyway. Been complaining to my wife about much she spends on groceries. Best to let that settle down. Still don't know if my 15 amp garage circuit will handle it though. Don't know how start-up amps work, how many amps the lights are pulling, etc. But since folks are using it on 15 amp circuits, I guess that's just worrying too much. Read plenty of reviews, and only one guy said his lights flickered.
--Vic
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On Thu, 10 Feb 2011 09:12:23 -0600, Vic Smith

Look around in the IR web site and get the installation/user manual PDF. I bet they recommend this should be on a 20a dedicated circuit. I have a similar compressor and that is what my book says.
If you have an amp of lights on a 15a you are pushing it. I guess pulling in another circuit is going be hard.
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On Thu, 10 Feb 2011 12:07:13 -0500, snipped-for-privacy@aol.com wrote:

No recommendation except call an electrician.
http://www.irtechpubs.com/ir_pdfs/Compressed%20Air/Air%20Compressors/Reciprocating%20Compressor/80444425.pdf

Might not be for an electrician. Don't know why I spent at least 50 bucks on fish tapes. Maybe I'll use them some day. I was going to pull 220 to the garage for a compressor some years ago. My brother said I could have a problem with corroded conduit. It's 1/2" I think, and underground the 30' from house to garage. So I just never got around to tackling it. Maybe I never needed the compressor so much?
But thanks. You mentioning 20a made me check my circuit box. Thought it was all 15's but there are four 20's.. When it's dark and my wife is home I'll turn on the garage door light on have her watch while I trip the 20's. Maybe I'm good to go. Now, do I really need that compressor.
--Vic
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On Thu, 10 Feb 2011 12:00:30 -0600, Vic Smith

If it is really a 20 you should be fine although you may see the lights dim when the motor is in locked rotor for the first half second or so on the start. Where you could have problems is if you had something else running and the compressor kicked on. I just looked and mine says 6.1 SCFM @ 90psi with the bogus "6.25" hp thing. Based on the nameplate FLA, I peg it around 1HP in an honest world compared to other motors. It might be 1.5 but that would be optimistic.
In real life who cares. The SCFM at the pressure you use most is what you care about. This thing will run an impact wrench if you have a fairly short duty cycle. The air chisel even has a shorter duty cycle (35-40%). Using a big paint gun is pushing it but if you watch your secondary regulator and stop when you see the pressure drop, you can paint. My big cup gun will usually go with about 75% duty cycle. Just about any compressor with enough pressure will run nail guns and such. I had 4 roofers, going as fast as they could go and the compressor was only cycling about 20% of the time.
I will warn you, once you get hooked on air tools, you will wonder how you lived without them. There is nothing better for working around your dock. You have no electrocution fears and lots of power. I borrowed a big air drill and I was spinning a 3/4" ship auger through SYP pilings. The only trick was holding on so you didn't get thrown in the water. They are air hogs. About half way through, I needed to stop and let it catch up.
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On Thu, 10 Feb 2011 15:47:34 -0500, snipped-for-privacy@aol.com wrote:

I don't have a dock, but one of my kids is a mechanic and has been doing all my car work. He's got plenty of air tools at work, but has no problem doing plenty of car work in my garage without them. A lot of cars, and doing stuff he would use air for if he had it. I wanted the compressor mostly for tires and sandblasting. Never had a problem turning a wrench or breaking a nut manually. He called yesterday and said his offer on a house was accepted. House has a nice garage. And he'll be farther away. I got a feeling at some point he'll ask to "borrow" the compressor for use in that garage, and I'll say "sure" because he does so much for me. But it will bug me a bit when I want to use the compressor and it's at his place. It's happened with other tools of mine. But like the other tools, I always end up figuring he's putting them to more use than me. And he's a good kid. So I get over it. He got most of my wrench sets, and what I did was eventually buy some new sets and lay down the law "These are mine, and mine only."
So now I'm thinking I'll get him the compressor as a "housewarming" gift after he closes. Avoid all the in-between stuff. Then see if I want to buy one for myself.
--Vic
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wrote:

Sometimes it is an 'investment' to get a son or son-inlaw some tools. Last Christmas I bought my son-inlaw a wire welder he had been looking at. Way more money than I wanted to give for a gift, but if I want something welded, he is only about a 15 minuit drive from the house. Beats me trying to learn how to weld to do a job I want done maybe once every two years.
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On Fri, 11 Feb 2011 12:33:32 -0500, "Ralph Mowery"

Yep. Gift selection is important!
--Vic
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On Fri, 11 Feb 2011 10:24:09 -0800, Smitty Two

I used to blast parts with glass beads when I was a heat treater. But I didn't pay attention to the compressor. Looks like I'll buy a wire brush for that instead.
--Vic
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On Fri, 11 Feb 2011 13:57:44 -0500, "Stormin Mormon"

No. I just butted in on this thread..

Yeah, had that happen, but not often at all. Always managed with a breaker, even it I had to add 6 feet of persuader to it. My kid is a truck suspension mechanic. Does it all, including fire trucks, loaders, etc. He NEEDS his air stuff.
--Vic
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On Fri, 11 Feb 2011 13:48:58 -0600, Vic Smith

Air just makes things happen faster. The best example is my assortment of nail guns. There are things you can do with a nail gun that you can't do with a hammer.
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On Fri, 11 Feb 2011 15:05:35 -0500, snipped-for-privacy@aol.com wrote:

About ten years ago I added a couple joists to my garages. Maybe 12 nails. Big ones, with a hammer. I've made a number of work benches, using drywall screws. Want to be able to take them apart if needed. Never needed to yet. If I did framing, I'd get an air nailer for it. The small compressor/brad nailer I bought when I put up new woodwork was maybe the smartest tool investment I ever made. Now I can't imagine ever using a hammer with brads again. I guess that's how you feel about your nail guns.
--Vic
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On Fri, 11 Feb 2011 14:26:16 -0600, Vic Smith

Brad nailers are the low end of my gun assortment but when I was putting the extra framing in my attic to meet the hurricane code, I can't imagine doing it without a framing gun. To start with, I wasn't banging with a hammer and cracking the drywall ceiling below. I also put on 7 squares of shingles on my addition without hitting my thumb once and that was a first for me in roofing. ;-)
I use my brad nailers on a regular Bevco CO2 tank sometimes when I don't feel like dragging a hose out.
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Vic Smith wrote:

It says it's got a 2HP motor on a 115V circuit, which is impossible according to a number of people on this newsgroup.
You might want to call IR and tell them they have a misprint. <VBG>
Jon
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On Feb 10, 3:41pm, "Jon Danniken"

Won't work on a 15A, 115V circuit. Should work OK on a 20A, 115V circuit however if there are no other loads connected. Note that current draw is listed @ 15A. You should not connect a motor that draws 15A, running, at full load to a 15A branch circuit.
Theoretically speaking, 2HP is 2*746W = 1492W or about 13A @ 115V, so even if the motor were 100% efficient it would still not be acceptable on a 15A circuit. (shouldn't load a circuit to more than 80% of its OCPD rating as a general rule, not sure if rules are different for motors or not. In the case of a 15A 115V ckt. that would be 1380W or 12A.) The compressor you describe draws 15A which is less than 20*0.8 or 16A so that is why I say that that should be OK, although it still might blow a fast-blow fuse on startup.
So, no, in short you shouldn't connect a 2HP motor to a 115V, 15A circuit (typical household circuit.)
nate
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N8N wrote:

Not according to snipped-for-privacy@aol.com, who stated "If it is 120v it will not be more than 1HP."
Surely you're not questioning the word of the almighty gfretwell?
Jon
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On Feb 10, 4:52pm, "Jon Danniken"

Here's what he actually said:
"1HP is not the absolute limit on 115v but if it has a NEMA 5-15 plug on it (15a breaker max) that is about all the motor you can reliably start."
I don't claim to be an expert on motors, but based on some cocktail napkin calculations, he's probably about right. Maybe a 1.5 HP motor would be OK, maybe it wouldn't, but 2 HP is definitely right out.
nate
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