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Old 02-14-2007, 05:11 PM
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air compressor

im looking to ge a compressor to do work on my car at home. i was told a 5hp setup would do just fine for all my body tools but while at home depot. the compressor said not recomended for air d.a sanders and such.

what can i use without buying the big industruial units. dont need that much air. i will be using my grinder, d.a. sander, air files, blue point long nose air chisel tools like these.

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Old 02-14-2007, 07:49 PM
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That is because that compressor at Home Depot is probably rated at 5hp PEAK. The peak rating is very deceptive and not very useful. Look at the SCFM (standard cubic feet per minute) rating for a more meaningful capacity of a compressor. FWIW, a true 5hp compressor will not have a 120vac cord.

A DA sander is an air hog and needs a true 5hp compressor to come even close to operating properly.

Vince
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Old 02-14-2007, 08:24 PM
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Exactly what 302 said, HP numbers don't mean zilch! The bottom line is the CFM rating is everything and if it is low then all the big HP numbers and oversized tanks that most of the econo compressors have will not help in the least. The biggest mistake most people make is running straight to the biggest tank in the store but a big tank does NOT make a big compressor in spite of common belief. The most common low end compressor that you can (practically) get by with will have about 3 to 3 1/2 true HP no matter what that phony "peak" or "maximum developed" rating says and will be 220 volt single stage, usually mounted on a 60 gal tank. Don't waste your money on a larger tank with a pump/motor in that performance range because it will not perform any better than the more common and cheaper 60 gal. As a simple guide look at the data plate on the motor it should be rated at least 15 amps and the CFM rating should be about 10-12 CFM at 90 PSI any less than that and you may not have enough air, even that is going to cut it close and that DA is going to work it very hard.
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Old 02-14-2007, 08:34 PM
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re: air compressor

The new indurstry standard is rating the hp as running hp not peak hp. I'm not sure how they define running hp but it sounds like there may be room for misinterpretation like so many of the things we buy. The other criteria is scfm as 302 mentioned and max. psi. The running hp from what I've researched may be rated as low as 2.3 when the max. hp is rated at 5hp. My campbell-hausfeld 5hp is rated @ 14.3 cfm and 175 psi with an 80 gal. tank. This is the old rating of 5hp. max. This comp. will keep up with a DA and all tools that I've used but it runs 75% of the time if I'm stripping panel with the DA. I would suggest using these specs. as a minimum. By the way I purchased this comp. 10 years ago on sale for 840.00 a great deal back then , hope you can find a similiar deal.
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Old 02-14-2007, 08:47 PM
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I have noticed lately that the newer compressors in the stores are being a bit more truthful about the power ratings, I guess losing those law suits over the inflated numbers got their attention . It got really ridiculous there for a while and it was easy to find 5 HP and even 6 HP 110 volt compressors, yeah right . Something that started to get popular a while back, but fortunately seems to have not caught on, was "tank assisted" CFM ratings which is TOTAL NONSENSE so don't fall for it if you see one.
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Old 02-16-2007, 08:28 AM
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My last compressor was a Sears 5hp 30 gallon.
The motor was a 110 volt 1 hp motor.
That's right- A 1HP MOTOR!
When I asked Sears about it they said
"it puts out like a 5hp motor" What BS!!!
I have a 5 HP Eaton now and it puts out MORE than
TWICE the cfm of the Sears one.
(They're both labeled as 5hp compressors)
I don't understand how Sears can get away with it.
It's an outright lie. False advertising.

BTW: Most DA sanders take 15 cfm at 90psi., that's a lot,
and my Eaton can barely keep up.
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Old 02-16-2007, 10:09 AM
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I don't think they make 5 HP 110 volt anymore (as if they EVER did! ) because of the law suits a while back but I may be wrong. I was in a Tractor Supply in Knoxville Tn a few weeks ago and I noticed that the compressors on the floor, the ones I looked at anyway, all had a more believable "running" HP rating so maybe this nonsense is going away. While this is much better it still really don't mean a lot because, as 302 pointed out, CFM is what counts no matter what the HP rating. To me it seems that the "tank assisted" CFM rating is far more misleading than those ridiculous inflated HP numbers but on the last outfit I saw it listed on (this was an Ingersoll Rand at Northern Tool!) was so far out of line I think most people will see it for what it is. I don't remember the exact numbers but it was about 46 CFM@90 PSI "tank assisted" for a 7 1/2 HP two stage mounted on an 80 gallon tank. This compressor is quite a performer when looking at the real numbers so using such ridiculous performance numbers does not make sense, I think it may cost them in the long run or at least I hope it does!

While on this subject I noticed that Ingersoll has one model at Tractor Supply and probably other stores that is 5 HP (running) with a single stage pump and a 60 gallon tank that is rated at 18.1 CFM@90 PSI. This is not a "tank assisted" rating and would seem to be a really good performer but then that is the problem here, it is too good for a set-up like this. While it does have 5 HP it is still just the very common inefficient single stage pump and appears to be nothing special. I looked at the specs and I can not see what the gimmick here is but they are stretching the truth to the breaking point on this one and those figures are just plain ridiculous. This would be good performance for a two stage outfit and I don't see any way a pump/motor combo like this one could get that much CFM. When buying a compressor one has to remember that the amount of air coming out the end of that hose is ALL that matters when determining how much air you will have available and all those ridiculously inflated numbers painted on the tank will not help your tools run any better.
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Old 02-16-2007, 10:23 AM
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Lots of good information here-

I purchased mine through Grainger, and it has handled everything that I have thrown at it (you can see it in my Journal)-I feel like everyone else here (pretty much), a 2 stage would be nice, but I get along very well with mine-It's a Model 3JR76 SpeedAire-5 h.p., 16.7 cfm @ 90 p.s.i., 230V single Phase-
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Old 02-16-2007, 11:06 AM
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35, As you pointed out a two stage is nice to have but it is not a necessity. It will run some cooler, last longer (usually) and produce a bit more flow than a single stage running the same HP but none of this is so big a difference that it means a single stage is no good, that simply is not the case. A good single stage for the average user is just fine and it is a fact that many thousands are being used very satisfactorily every day and if it does the job it may be just the ticket for a lot of people. I think the single stage design gets a bad rap mostly because of the "hobby" type 110 volt units and the JUNK oil-less compressors out there but these are in NO WAY a gauge by which to measure the performance of a good single stage compressor.
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Old 02-16-2007, 01:51 PM
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Well said, Old Red
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Old 02-16-2007, 02:16 PM
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We used to sell Eagle Compressors at the NAPA store that I worked at, and now we are selling them at the place I work for now.

They have a new line called "Max Air", but I haven't studied them enough to spot the differences ... other than yellow paint and 2-yr warranty.

Here are a couple of 18.5 CFM @ 100 PSI, 230V, single phase, single-stage, cast-iron compressors.

"Montea" (a member here) bought one of these MaxAir compressors in Calgary, Alberta for less than $1000.00 CDN if I recall correctly.


"MaxAir"



"Maximum Performance"

Thier site also includes an Air Power not Horsepower article, which says many of the same things mentioned in this thread.

PS
I just read thier "Standard Warranty" on the Max Perf line ...
12 mos from start-up
OR
15 mos from manufacture date ...
whichever comes FIRST

Translation: if it sits in a showroom for 12 months before you buy it and take it home ... you get THREE months?
I gotta phone the rep and ask about that, and I suggest you do the same ... and get the answer in writing.

Last edited by 66GMC; 02-16-2007 at 02:25 PM. Reason: Warranty
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Old 02-16-2007, 03:33 PM
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That looks like a much better set-up than the usual inline twin cylinder design that is so popular and which (twin cylinder) is on the Ingersoll I mentioned earlier. However, just like on the Ingersoll, I can not help but find those performance numbers to be HIGHLY suspect. Compare a similar design from Eaton (a company that has the very strange habit of telling the truth about it's products) that I looked at recently, this has a similar three cylinder semi-radial design and has 4 1/2 HP (19 AMPs/230 volts) compared to the MAXair's rating of 5 HP (21 AMPs/230 volts) the Eaton has 14 CFM@90 PSI as opposed to the 18.5 CFM@100 PSI for the MAXair. That extra 4 1/2 CFM (at a 10% higher pressure to boot!) is a VERY significant difference for only an extra 1/2 HP and I very seriously doubt it is capable of that kind performance. This is not to say it is a bad outfit as it most likely will out perform most of the more common designs of the same power but if someone selects that unit counting on that much air they will most likely be disappointed. I have obviously not tested this outfit but I have tested many compressors of different types and sizes over the years and I have never seen any kind of single stage piston compressor make near that much air on only 5 HP. I am not pushing the Eaton, actually my favorite is Quincy, it is just that they are known for being honest about their ratings and make a really good comparison-14 CFM@90 PSI for the Eaton vs 18.5 CFM@100 PSI for the MAXair, around 30% more air flow at 10% higher pressure with only an extra 1/2 HP-I don't think so
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Old 02-16-2007, 11:54 PM
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Boy are you guys right, three years ago I bought a Craftsman vertical 30 gal. 6 hp (BS) 115v, and it works just fine for normal stuff. But now I,m building a '32 Ford and using bigger air tools and this compressor just can't hang. After looking at the specs I saw that it puts out a whopping 6.4 cfm @ 90 psi !! and the motor does'nt even have a hp rating on it. Well its for sale now and I,m looking for a 60 gal 230v single phase unit, don't need huge. Lowes is advertising a "Kobalt" 60 gal. 7 hp "peak", 13.3 cfm @ 90 psi for $499. Sounds pretty good to me, think I,ll go take a look.....
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Old 02-17-2007, 01:18 AM
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picked this one up at a menards some years ago -10cfm@90psi-----12cfm@40psi --125 psi max 60 gal 6 hp at 220v. Got it for a little over $350 and runs my air grinder but at full draw it slows down some. Recovery is fast that is a plus. It will run the DA just fine since i dont run it at full power anyway just to keep heat down on steel.
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Old 02-17-2007, 06:08 AM
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I have that Eaton pump that was mentioned. It does a good job, but will not keep up with a DA when I am stripping a car. For most other stuff it does great though. For the average person at home, it would be just fine. If I were going to buy another compressor, I would probably go with a 2 stage just for that reason though.

Aaron
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