..There are six things you need to know about compressors: The maximum PRESSURE that it develops, the rated VOLUME it can deliver, the amount of compressed air it can STORE, how LONG the motor can run (which is also known as "duty cycle"), how much electrical POWER it's going to take to run, and how much NOISE it's going to make....
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Hi, Also whether compressor is lubricated or not. Never get non-lubricated one. I have a Campbell Hauser Extreme duty belt driven compressor which can be powered by either
120V or 208V. I am running it on 120V plugged into regular wall outlet in the garage. For what I do it is adequate. It can even blow sprinklers in the fall.
All the advice in the article is good stuff. One critical point is missing, however, The author should have added a section named "Delivery". More power is wasted by undersized or over long hoses and restrictive couplings than any other feature. The ubiquitous 1/4" Milton M fittings almost everyone buys are serious offenders in that respect. That is why so many shops for years kept buying air compressors with higher and higher tank pressure ratings. The currently popular 175 PSI rating is absurdly dangerous because design parameters of most air tools are by regulation pegged at 90 PSI. Milton some years ago introduced the "V" series plugs and couplers. These have substantially higher flow rates than the "M" series which
98% of the lads reading this now have in their shop. The specs are listed in the Milton catalog available (PDF) online. I converted my shop some time ago when they were first introduced to improve my HVLP paint systems. Couple this with a good quality 3/8" air hose (throw out those wretched 1/4" hoses) and a modest 125 PSI compressor will serve you very well for everything but removing earth mover wheels. The laws of physics will work for you if you let them.Joe
General rule for air compressors is buy the biggest one you can afford, because you always seem to need more air later than you thought. Mine is a "5HP" (yeah right) oiled reciprocating compressor which is just
*barely* adequate to run my abrasive blasting cabinet. Had I know I'd get one of those, I'd have bought a larger compressor in the first place, though what I have is about as big as you can run from a 120V circuit.
If you are talking about using the compressor only for power tools and general use, I agree with the lubricated vs non-lubricated. If you plan to use that compressor for painting, I would recommend the non- lubricated. You don't want oil in the lines when painting.
On Thu, 11 Dec 2008 18:21:06 -0800 (PST), BobR cast forth these pearls of wisdom...:
Not true. A lubricated compressor is better for all wood shop uses than an oilless compressor. The oilless models are throw away, light duty, short lived compressors, and they make a ton of noise. Whether the compressor is lubricated with oil or not has no bearing on its use for painting. I think what you were thinking of was whether to use a line oiler. Certainly, if you're going to paint with that system, do not install a line oiler. Simply oil your tools through the chuck, as needed.
Good luck finding a single automotive paint shop, or pro business in general that gets by with an oil-less compressor. They're noisy, hot running things that burn out if you run them too hard. A good oil lubricated compressor exhausts a negligible amount of oil, and you need a really good filter and moisture separater in the line for painting anyway.
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Admittedly, my post does not dovetail with this thread since you're talking electric motor driven compressors. However, I simply must brag and chortle about my air cooled DIESEL milsurp air compressor. Apparently it was designed to air up tires on jets. It's similar to the "wheel barrow" compressors that carpenters use. It has a single tank and a two stage compressor (175 psi!) compressor, belt driven by a Yanmar 3 hp, fuel sipping, air cooled engine. It is well balanced and light weight. It CHURNS out air. It starts from a battery or with a rope. I swoon over its efficiency, reliability, and fuel economy. In fact, I think I'll go give it a hug right now. Vernon
Admittedly, my post does not dovetail with this thread since you're talking electric motor driven compressors. However, I simply must brag and chortle about my air cooled DIESEL milsurp air compressor. Apparently it was designed to air up tires on jets. It's similar to the "wheel barrow" compressors that carpenters use. It has a single tank and a two stage compressor (175 psi!) compressor, belt driven by a Yanmar 3 hp, fuel sipping, air cooled engine. It is well balanced and light weight. It CHURNS out air. It starts from a battery or with a rope. I swoon over its efficiency, reliability, and fuel economy. In fact, I think I'll go give it a hug right now. Vernon
Now Vernon, you weren't over there squeezing her jugs now were you?
Up North. Noooo. But I was tweaking her nipples! V
Step 1. Decide what you need.
Step 2. Multiply that by 1.5 - 2.0
Step 3. Shop for a high quality two stage, or a two piston oil crank compressor if you only need a small one.
Step 4. Consider used, as you can sometimes get a killer deal on a big one.
Step 5. Install it right, electrically, piping, and air dryer.
Step 6. Enjoy and use, knowing you won't fry it, overwork it, or have it fall short when you need it the most.
My observations from not following these steps.
Steve
If I were ever to buy a stationary compressor, it would be one that you wouldn't be able to run on a 120V circuit. A real 5HP one sounds about right...30A at 240V.
Chris
And noise. Put it somewhere NOT where the people are. Use big shock mounts and flexible lines to avoid coupling.
Some of the auto paint shops in my area have switched to turbines and HVLP guns for use with water based finishes that get destroyed by the smallest amount of oil.
Not a bad article, if you don't mind the tone of the Very Authoritative Home-moaner.
But as far as size goes, buying small-ish isn't necessarily a bad thing, as compressors are simply additive. Three small compressors should be exactly equivalent to one big one, with a few advantages:
Proly some other advantages, as well.
HD/campbell hausefeld has a very nice upright 30 gal compressor, dual voltage motor, belt driven cast iron compressor w/oil, sight glass, wheels, VERY quiet. I would buy multiples of these in a minute.
Also, in many cases, larger resevoir volume is all that is needed, not a bigger compressor. I have numerous small makeup tanks for about 70 gals, works great with one small compressor. Would work even for air tools, depending on how much you use them vs. your total gallons.
5HP on a 120 volt circuit? Somebody is pulling your leg, but looks like you realize it! I bought a Porter Cable 7HP, (sure you betcha), 60 gallon tank compressor a few years ago. Motor amps tell me that it is closer to 3 HP. It does all I want it to do. I can run any air drill, DA sander I have, and it just about keeps up. And what I mean by that is for a home, weekend warrior shop it is just fine. I don't drill or sand continuously for hours on end. By the time the tank starts to run a bit low I am ready for a 30 second break, and the the compressor catches up again. Really I don't even notice any short comings. If you planed on running a sander continuously with no break at all it will not keep up. In my opinion, most any one man home shop can get along nicely with 10 CFM at 90 PSI. Greg
I will argue that point! Seems to me that the larger HP cast iron pump compressors are very quiet, certainly when compared to a 1HP oil less unit. My cheapy 7HP, (really about
3HP) Porter Cable is quieter than the 1-1/2 Craftsman it replaced. Much quieter than the oil less models we have at my job. Some of the 5HP cast iron compressors are strangely quiet. Low RPM pump and motor reduce noise a bunch, but at a premium price. Greg
Hi, My main goal was to use it to blow sprinkler system in the fall. What I got does it OK but very slowly. Wish I had a bigger one. Then I hve to run 208 circuit for it. As a compromise I am happy ith what I have. That Hp rating is bogus. They don't tell trun Hp, they invented a term peak Hp to fool general consumers. They do the same with stereo system. When they brag about 200W output power it is barely 50W rms.
175 lb. is not enough pressure for many Jet aircraft tires, and most of the time dry nitrogen is used because of that fact. I remember a couple of jets taking 250 lb. in the mains. The Jetstar was one.
John
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