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pgmrdan
10-28-2009, 05:34 PM
The wiring on my outbuilding was finished yesterday. I had the electricians wire up a 220 circuit for an air compressor.

After looking at Lowes and Home Depot this morning I'm not sure either of them have what I need.

A couple of years ago I had a good idea on what I needed but now (and maybe for a quite a while longer than that) with HVLP paint guns being so popular I'm not so sure of what I need. (I'll primarily be working on my tractors and an old car but I'll be doing other things too like painting the metal patio set and reparing small to medium sized farm equipment.)

Is an HVLP gun going to be the biggest user of air on my compressor? How many SCFM do they need and at what psi?

Other things I'll be using are impact wrench, DA sander, cutoff tool, die grinder, etc.

Will a good 60 gallon unit be plenty or should I go 80 gallon as one of the 'experts' suggested?

Please recommend good brands of compressors or at least electric motors to look for.

Also, I saw one compressor with 3 cylinders. I don't think I had ever seen one before. Is that something new?

Thanks,
Dan

Bill Pace
10-28-2009, 05:53 PM
DA sander, cutoff tool, die grinder, etc.

An HVLP gun will run on most anything, but these are 'air loving'. A DA sander will really work a compressor trying to keep up with the air being pushed thru it --- air files, die grinders, impact wrench - these like lots of air.

I'm kinda guessing here, but I think you would need to get above 15-16 cfm capability on your compressor to keep it from running constantly. And, thats not to say you cant get a lot of work done with the smaller units - heaven knows there are thounsands of pancakes & 10-20-30 gal ones out there running every day, - but if you can stand the finances now, its definately better to go ahead and get a good sized one.

airsmith282
10-28-2009, 05:58 PM
paint guns really dont use that much Psi or CFM, i have a CH paint gun that came wiht my compressor and never had an issue yet, also i recently gota breating machine, forma buddy long sorty but it puts out 15psi which i found is more then good enought for my paint gun or an airbrush kit, and the best part its 115 volt and no tank its 100% supply of non stop air, , as for the air tools you want to use id say for better performance 9 cfm at 90psi would be idea, 18 cfm is better but 9 is more then good at 90 psi and it would run higher cfm on lower psi no idea the numbers there but, its really boils down to your needs wants personal choice and budget ..

its taken me over 4 years but now i can afford a 4 jow chuck for my lathe and a few other toys for my lathe longer story there any how

all the best in your choice, but its still up to you in the end,i even use my 8 gallon ch machine for all my auto motive stuff and sandblasting now if your going to need to sand blast then get as much CFM as you can afford other wise it takes forever to blast anything big,,,

ok thats my thoughts

lazlo
10-28-2009, 06:11 PM
I'm kinda guessing here, but I think you would need to get above 15-16 cfm capability on your compressor to keep it from running constantly.

That sounds right. I have a single stage 3HP Ingersoll Rand that's 12.5 CFM that runs constantly when I'm using a die grinder or da sander.

An HVLP gun uses very little air, by comparison.

Whatever size compressor you pick, it's going to end up one size smaller than you need ;)

pgmrdan
10-28-2009, 06:31 PM
For the past several years I've been using an oilless, 25 gallon, 135 psi, porter cable compressor with a vertical tank on wheels. I love that little thing. It's light and portable. And since it's oilless I can lay it on its side in the back of the truck to haul it to where the work is. It will do everything so far but for some things it seems to take forever.

The toughest task I've had it do is power my impact wrench to remove the 3 blades from my Gravely zero turn radius lawn mower. No way could I have loosened the nuts without an impact wrench. Even the guys at the shop where I bought the mower said it's a snap with an impact wrench but good luck trying to do it without one.

Anyway, 80 gallons seems way too big but I've never done any really demanding work at home for an air compressor.

Thanks for the replies and keep 'em coming. I'd still like to have some good brands listed.

Dan.

Black_Moons
10-28-2009, 06:31 PM
Never buy 'oilless or maintence free' compressors, they are 10x noisyer and last 1/10th as long as oil filled. for painting you just get oil/water seperators and/or dessicators to put inline (need water seperation in an oilless compressor anyway)

6cfm is the biggest you can get from 120v 15A circuit, or 7.5A at 240v (some are dual wired)
Insure the compressor rating is 6cfm at 90psi or higher, some compressors cheat and spec 6cfm at 40psi and at 90psi its only like 4cfm. Ignore the HP ratings of 'small' compressors as they lie like shopvacs. 5hp from a 120v socket is never gonna happen.

it will run HVLP paint guns all day long (well not all day long but painting is intermitant so it will catch up) Die grinders and cutoff tools are usable if you don't mind being intermitant (use of carbide burrs will greatly improved metal removed compaired to grinding stones) fine for light usage of impact wrench but id recommend 10gal tank min, idealy 20gal tank.

12cfm is your typicaly 3hp~ compressor, 15A at 240v, it will run die grinders continiously, impact wrenchs as much as you'd want, most other tools

16cfm is your typical 5hp compressor (20A~25A circuit, will brownout your house a little when it turns on), comes with a 60gal tank, the 80gal tank is just gonna waste more space IMO. the 150/175 psi diffrence of medium and high end compressors is a minor help.. 175psi can require you to buy more expensive regulator/filter however.

16cfm will actualy start running small sandblasters (still not faster then sanders unless the area is highly detailed) and DA sanders continiously, as well as easily run die grinders and air drills (500rpm air drill + 16cfm compressor = AWSOME, you can use 6" holesaws through steel. or drive 3+" deck screws into solid wood at 300rpm and stop on a dime. also it has no stall kick, it just stalls with the same torque as it was running with)

The common '3' cylinder air compressor ($900 avg cost).. im not sure if they are all like this, but mine is NOISY, super super noisy, even after removing the belt guard its so noisy I need to move it outside (try taping the belt guard on one before buying it, if it rattings with a good hit, it will make the compressor 2x as noisy)

Iv seen one or two of the 2 cylinder 2 stage 16cfm/5hp compressors and they are MUCH quiter, but often go for $1600~2000 with tank (but usally 80gal 175psi vs 60gal 150psi of the other 16cfm compressor)
Thinking of just buying one of those cylinder heads for my compressor.. but they are like $400 heh.

As is, I run two compressors, a 6cfm 20gal 115psi thats so quite you can talk over it, it lives outside and is allways pumped up and its cutoff valve open. pumps up once or twice a day, its great for painting, casual die grinding or sheet metal cutting with the nibbler, anything thats not gonna take more then a few mins.

And a 16cfm 60gal 150psi thats indoors.. and too friggen noisy to wanna ever use so I only turn its shutoff valve on when I need to use it, cause when it pumps up at 3am it wakes up everyone in the house. the 6cfm you can't even hear inside. Both compressors actualy share the same 20A 240v circuit

PTSideshow
10-28-2009, 06:35 PM
A couple of important things to look out for. One of Kobalt's compressors is called PEAK horsepower That is a marketing BS as you can only measure Peak HP for a mirco second at start up.

Another thing to find out before buying is what exactly does SCFM mean for that compressors manufacturer's.

The correct definition is STANDARD CUBIC FEET/MINUTE and only that.
That is the amount of air @ a certain temperature over a period of time.
No buzz words like sustaining, silenced or any thing else is hype.
Same with the horse power rating of the motors Peak is bogus, start up or any other advertising hype they can come up with.

Buy more compressor than you think you need. As much or more than you can afford. OR wait and save up for the next larger one.

The HF assembled in the USA one's are assembled in Rock Hill SC. By the atlas copco company. They are from Italy and one of the largest mining and construction compressor makers.
The tanks are ASME stamped made by Manchester tank company here in the USA. As are most of the others that are assembled

Here is the 800 number for the parts warranty in Rock Hill SC. 1-866-869-3114

They also make 7 other brands at the same site.

By the way Husk Pro, some Campbell Hausfields and Kobalt are assemble in the same plant here in the states. They all all have the same parts warranty 800 number. 1-800-543-6400
Any of the pumps that have a VH in front of the number on the id plate of the above compressors are China units.

Ingersoll Rand @ Tractor supply are also made in the USA thier 800 number parts warranty is 1-800-AIR-SERV

Pumps, motors, and hardware and electrical controls and assorted parts. Can be made in any country, Mexico, China,US,Italy, or other. All the ASME tanks are made in the USA and carry the stamp.

The motors and other parts change the country of origin with each shipment.

The other thing to look out for is at home Depot they were trying to pass off a rebuilt as new and at new prices. Somebody peeled the tape off that was applied over the engraved re built info. But they also left the paper work in the envelope from the company that did the work.

Check the dates on the name plate. These were over 2 years old.
:D

Buy more compressor, than you need as it has been said you will need it tomorrow.

coollx
10-28-2009, 06:38 PM
If you are looking for a high quality compressor that will last I don't think the ones sold at Lowe's and Home Depot will do. Their's tend to be homeowner grade which is probably OK for casual use like pumping up tires and low volume spraying.

I've owned a few compressors and, except for one I sold and shouldn't have, you almost never have enough air volume. I think the DA sander will be a tool that consumes alot of air followed by the die grinder and cutoff tool. The impact wrench is a very low volume tool. Although I don't own a HVLP spray gun, I think one could require a fair volume of air.

My suggestion is to buy the best compressor you can afford. The brands I'd recommend are Ingersoll Rand, Quincy, Atlas, Champion. I'd get a two stage compressor with cast iron cylinders, a real 5 HP motor and a 80 Gal tank. Most good two stage units will produce about 15-20 cfm at 90 psi which is what you want.

Hope this helps.

hardtail
10-28-2009, 06:44 PM
I would shoot for 15 cfm @ 90 psi as your minimum goal, compressors often are like building shops, once they're there you wish you went bigger, I've got a couple Devilbiss, one around 5 cfm, the other around 11cfm and have bought one of those triple pumps and a 60 gal reciever as a third unit. I've seem the triples configured as single and 2 stage and externally they look identical but maybe the valve internals on the 2nd stage head is different, anyway they rate them at 18.5 cfm. I would look for lubed cast iron pumps and the slower they run the longer they last, going bigger and slowing it down used to equal decades of longevity, a 60 gal tank should be lots.........

radkins
10-28-2009, 07:16 PM
Will a good 60 gallon unit be plenty or should I go 80 gallon as one of the 'experts' suggested?


All else being equal you will see exactly zero difference in whether your tools keep up or not between a 60 gallon and an 80 gallon tank, there will be a slight difference in the number of times it cycles during use but that's all. The size of the tank has next to nothing to do with how well a compressor keeps up in spite of common belief but a bigger tank will cut power consumption SLIGHTLY and Slightly reduce wear and tear, this is due to fewer high load start up cycles. A lot of guys think a bigger tank provides reserve air that will make a compressor perform better but it simply does not work that way, if your tool's air consumption exceeds the CFM rating of the pump you will still run out of air and a bigger tank will not help. An extra 20 gallons of storage will provide a little more time initially (usually just extra seconds however) but then that will be lost to the extra time it takes to refill the bigger tank so it is just a trade off and you will not gain anything. The bottom line is the size of the tank should be one of the last considerations (as long as it is reasonably sized of course) when selecting a compressor with CFM being the first along with pump size and type. Motor HP should be based on the AMP rating and never on what the manufacturer claims for HP, these HP numbers are almost always pure BS but that AMP rating is the required federal data and they will not lie about it. The CFM going into the tank is what really matters but people see the tank and a big tank may make a compressor LOOK big but this is one place where looks are deceiving. 60 gallons or 80 will be just fine and the 80 may offer some benefits in service life and power consumption, although power consumption reductions will be very small, but it will not make better performance.

NEVER pass up higher CFM for a bigger tank! For example a compressor with 15 CFM and a 60 gallon tank will handily outperform one with 13 CFM and an 80 gallon tank, the size of the tank simply does not make the difference that a lot of guys think it does.

camdigger
10-28-2009, 07:29 PM
With all these big compressors, how often do you drain condensation from the tanks? Do you fully depressure the tank when draining condensation?

I have a 5.7 cfm 20 gallon unit I drain daily(at least when I remember:o). I often leave it with the drain valve open and the power shut off for weeks at a time....

Black_Moons
10-28-2009, 07:46 PM
I allmost never drain mine :( yea I know, bad, but it only sees use once every week or so, so once a month and it spurts out a cup.. never let the entire tank depressurise.. infact I leave it at full pressure and just turn off the shutoff valve and it can go an entire week without turning on to pump up again.

But yea, tank size does not matter much unless your compressor can't keep up. I would never buy a smaller then 6cfm 20gal compressor though, as iv seen people use those small ones and they are lucky if they can get 1 bolt on/off with thier tiny impact gun before the tank is empty.

Doozer
10-28-2009, 08:12 PM
I have a 3hp Emglo compressor that I have found to have the best specifications of any I have seen. Emglo was part of Davey Tree Service and has been sold to Dewalt, where they changed them into light duty, Home Depo kind of cheese. The old cast iron ones are now made by Steam Jenny corporation.
Anyhow, the specs are 3hp, 220v and 20 amps I think. 16 cfm at 90 psi. 4 cylinder, single stage. I set cutoff at 110 and cut-in at 90. This thing is quiet, due to the low pump rpm.

http://www.jennyproductsinc.com/

--Doozer

lazlo
10-28-2009, 08:36 PM
My suggestion is to buy the best compressor you can afford. The brands I'd recommend are Ingersoll Rand, Quincy, Atlas, Champion.

Quincy and Champion are the Rolls-Royce of compressors, but Mike and I have the same 230V, 3HP Ingersoll Rand (12.5 CFM), and it's an Indian compressor with a Chinese motor.

Mine's been fine, despite abusive cycle times (i.e., running a DA sander constantly for hours on end), but Mike's had been busted at least twice that I know of...

hardtail
10-28-2009, 09:37 PM
I'm surprised radkins went that easy..........grin........I forgot to say or reconfirm my similar philosophy, watch out for the POS compressor motors that are overrated.........they take a light duty motor, spin them at 3450 and get some outrageous hp claims, I've got a real 1740 rpm 3 hp that will run the 18.5 pump and it weighs all of 80 lbs..............and best of all a low rpm pump for longevity.

wierdscience
10-28-2009, 10:25 PM
Running a DA or any other vane motor driven tool will require a true 3hp compressor,but what if you want to add a bead blast cabinet?

Personally I wouldn't consdier anything less than a 5hp 60 gallon tank unit.

This Quincy has free shipping:)

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200350476_200350476

motorcyclemac
10-28-2009, 11:23 PM
I would highly recommend buying a Quincy. They are the very best. That compressor mentioned above is a helluva deal..If you can afford the deal...do it. Looking at those specs it actually outperforms my 6.5 hp unit by quite a margin. They are running 175 at the tank and they have a higher CFM rating...on 1.5 horse less.

I have a 6.5 horse 'Husky' with a cast pump and Emerson motor mounted on top of a 60 gallon tank. That compressor then dumps into a 40 gallon tank and finally into a network of 3/4 copper pipe. I probably have 125 gallons of reserve air if you include the pipe volume.

That being said..when the Husky dies I'll replace it with a 7.5 horse Quincy on an 80 gallon tank...and put the old Husky 60 gallon tank in the line..

I like a lot of reserve space. I have the room and it just adds time between cycles.

Cheers
Mac.

radkins
10-28-2009, 11:42 PM
With all these big compressors, Do you fully depressure the tank when draining condensation?I..


Never completely de-pressurize a tank unnecessarily as it will shorten it's service life, probably won't matter much on a small tank however. A tank will expand and contract even during normal on/off pressure cycles but this effect is much greater if the tank is allowed to decompress fully and the excess expansion and contraction will lead to metal fatigue that can cause cracking, usually around welds at the mounting feet or motor/pump mounts.

radkins
10-28-2009, 11:56 PM
I would highly recommend buying a Quincy. They are the very best. That compressor mentioned above is a helluva deal..If you can afford the deal...do it. Looking at those specs it actually outperforms my 6.5 hp unit by quite a margin. They are running 175 at the tank and they have a higher CFM rating...on 1.5 horse less.

I have a 6.5 horse 'Husky' with a cast pump and Emerson motor mounted on top of a 60 gallon tank. That compressor then dumps into a 40 gallon tank and finally into a network of 3/4 copper pipe. I probably have 125 gallons of reserve air if you include the pipe volume.

That being said..when the Husky dies I'll replace it with a 7.5 horse Quincy on an 80 gallon tank...and put the old Husky 60 gallon tank in the line..

I like a lot of reserve space. I have the room and it just adds time between cycles.

Cheers
Mac.



You would be much better off to just use the 80 gallon tank and let it go at that, what you are suggesting is what I was talking about earlier and is a big mistake that will cost you performance instead of making it better. You gain exactly nothing by adding all that tank capacity because any extra time you think you are getting will only be lost to the excessively long time it will take to fill all that empty tank space, any and all extra run time is going to be followed by a proportionally longer recharge time so what do you gain? You can actually hurt your performance instead of gaining because the excessive run times during the prolonged recharge will cause heating of the pump which will reduce efficiency, this means you will actually lose performance instead of gaining anything. The size of the tank relating to how well a compressor performs is probably the most misunderstood part of a compressor as a unit and it may be hard to make some understand but too much tank for a particular motor and pump combo is as bad as not enough, a 60 gallon in series with an 80 gallon is way too much even for that Quincy you mention especially if you attempt to use the 40 gallon also!

motorcyclemac
10-29-2009, 12:04 AM
Hmmmm.....Ya know...I guess I never contemplated what you are suggesting. Makes sense. I simply dismissed the charge time because I don't drain the tank all the way down. I burp the water every night...but leave the pressure up. It does take an added minute or so to recharge during use so I assumed that added 40 gallon tank wasn't hurting anything. It does go a bit longer between cycles at the cost of a minute or so longer on cycle.

I have zero....nada...no leaks in my system and thus it holds air for a LONG time without pressure drop. I might lose 1-3 pounds a week if I don't use the air. That being said, recharge time wasn't really a issue in my thinking.

You think I should remove that 40 gallon tank?

Cheers
Mac.

Falcon67
10-29-2009, 12:11 AM
http://raceabilene.com/machine/images/AirSystem_A.jpg

Does everything I need, including cylinder head porting. $399 at Tractor Supply. about a 10~12 SCFM unit.

This was shot with a 8.9 SCFM @ 40, 25 gallon 1.5HP 110V Porter Cable oil bath iron sleeve unit using an HVLP gun and single stage Fulthane.
http://raceabilene.com/scratch/scoop9.jpg

The car under it was shot with a oilless CH compressor - Done it, lived to tell about it, don't go there.

Your biggest issue with paint is water control and the best way to handle that is with either a dryer unit or lots of well layed out piping.

radkins
10-29-2009, 11:07 AM
I have a 6.5 horse 'Husky' with a cast pump and Emerson motor mounted on top of a 60 gallon tank. That compressor then dumps into a 40 gallon tank and finally into a network of 3/4 copper pipe. I probably have 125 gallons of reserve air if you include the pipe volume.Mac.


If you have the compressor I think you have that HP rating is probably a "peak" rating and the pump is a single stage? Look at the motor data plate and I think it will be the very common Emerson 15 AMP 5/8" shaft motor which puts out a "real" HP rating of about 3 1/2 or just about half of what they claim. The good news about this is that 3 1/2 HP is not at all bad and in fact is about right for that pump/tank combo it is just that we have been exposed to the grossly inflated peak HP nonsense for so long that when we see real HP numbers we tend to think of them as weak which is simply not true! As far as the extra 40 gallon tank being a problem that would depend on how you use your compressor, if you run out of air often and have to wait for it to recharge then it could be hurting your performance but if not it won't really make much difference either way. If you run out of air often and find yourself having to waiting on recharge and you remove the tank you will still have just as much "run" time during any given work period but you will have more on and off cycles. If you leave the tank in place you will still have the same work vs wait times just that they will be fewer but longer and the longer recharge time is where the problem is. With an excessively long run time you will have the pump temperatures rise because of the excessive duty cycle which will cause a slight reduction in compressor performance and this could lead to reduced work vs recharge times even if it may not seem that way. Whether you lose any performance or not would depend on several things however even in a best case performance can not be gained. As an example if you run 2 minutes and wait 3 with the small tank that would be a 5 minute cycle and in 30 minutes of work time you will go through 6 cycles with a total of 12 minutes work time and 18 minutes waiting. If you then doubled the tank capacity but used the same pump and motor you should get 4 minutes work time but would then have to wait 6 minutes for the recharge so in the same 30 minute work period you would now go through only 3 cycles but you still end up with the same total of 12 minutes working and 18 minutes waiting. These are of course just example numbers and your actual numbers will in all likelihood be quite different but the principle will remain the same, if you double the tank size you double the time it will run before running out of air but you will also double the time it takes to recover. The problem is that this usually is not an even trade off and too much tank leads to the heat and efficiency problems that cause the wait vs run times to actually increase with the bigger tank.


This certainly does not mean that an 80 gallon tank is bad on a compressor that came with one. When a compressor is designed the tank size is chosen by taking into consideration the HP, CFM and the intended purpose so how the thing comes equipped from the store is usually the best way to leave it except in very specialized situations. Adding tank capacity to an existing design is at best an exercise in futility and in a worst case it can be, and often is, a losing proposition!

Black_Moons
10-29-2009, 05:04 PM
Oh, one benifit of larger/multiple series tanks is more time/space for the air to cool and condense out moisture. Remember the output air of your compressor (cylinder itself) is likey at least 60c even with those fined style tubes, and much more if its just straight copper to the tank.

ulav8r
10-29-2009, 06:21 PM
A compressor like Falcon67's would not be a bad choice for the use you specified. Then when you decide you need a sandblaster, get another compressor just like it and manifold/run both to supply the blaster.

radkins
10-29-2009, 07:10 PM
Oh, one benifit of larger/multiple series tanks is more time/space for the air to cool and condense out moisture.


Actually that is an old trick and it works quite well if the system don't have enough piping to cool the air sufficiently. A small tank mounted vertically with the incoming air near the bottom and the take off at the top makes a pretty good setup. I have seen several of these made using an old driveshaft standing on end with a fitting for the incoming air about 18" or so from the bottom end with the take off air fitting at the top.

motorcyclemac
10-30-2009, 02:39 AM
[QUOTE=radkins]If you have the compressor I think you have that HP rating is probably a "peak" rating and the pump is a single stage? Look at the motor data plate and I think it will be the very common Emerson 15 AMP 5/8" shaft motor which puts out a "real" HP rating of about 3 1/2 or just about half of what they claim. The good news about this is that 3 1/2 HP is not at all bad and in fact is about right for that pump/tank combo it is just that we have been exposed to the grossly inflated peak HP nonsense for so long that when we see real HP numbers we tend to think of them as weak which is simply not true! As far as the extra 40 gallon tank being a problem that would depend on how you use your compressor, if you run out of air often and have to wait for it to recharge then it could be hurting your performance but if not it won't really make much difference either way. QUOTE]

Thanks for the input. You are correct in the assumption of what compressor I have. You nailed it with your description. It is a single stage pump.

I don't really run out of air. I can run my die grinders...or other vane driven air motors wide open and the pressure rarely drops below 90 psi. The pump will keep up while the die grinder is running and will actually reach 135 again and shut off. I will have to do a time test by charging up to 135 and bleed down to start pressure and time it with and without the 40 gallon tank. See if it really is adding a lot of recharge time.

I'll post the results after I do it.

That Emerson motor must be one inefficient lump if it is rated at 6.5 horse and only puts an actual 3.5 to the pulley. Maybe I should replace it with a 3.5 horse Baldor and save the power bill?

Cheers
Mac.

Black_Moons
10-30-2009, 12:29 PM
the motors 6.5HP rating is complete fake and based on random numbers pulled outta a marketing execs @#$ and doesnt relate at all to how much power your motor draws or could produce (unless stuck by lightning).

infact it draws the exact same as all 3hp electric motors, +- 10%. if it really drew 6hp worth of power that would be 2000W of heat it was disipating and it would get as hot as an industral space heater. (and blow 20A 240v brakers btw) Its just a 3hp motor, no less, no more, replacing it with a baldor would only get you slightly less noise/vibration (and likey longer service life, but do that AFTER your existing motor kicks the bucket)

Similar to how with audio amplifyers, PMPO means aboslutely nothing at all, it can be in excess of 200W for a system with only a 40W power supply (and speakers with impedances that could never draw more then 40W's even dead short to the power supply)

And to a lesser extent, how lawnmowers are sold by ft/lbs of torque with no RPM rating for the torque messurement (Ok now im getting picky)

Or how 'modifyed sine' is really a squarewave. Or how my 120v 10A shopvac is rated 5HP+ yet has the exact same CFM/PSI specs as every other shopvac rated from 2hp to 10hp (Also all drawing 10A at 120v, Boy I gotta start selling shopvacs to free energy people)


I hate marketing departments. Don't believe everything you read, even if its a parts ratings :( (Well, at least a parts 'peak anything' ratings)

lazlo
10-30-2009, 12:36 PM
the motors 6.5HP rating is complete fake and based on random numbers pulled outta a marketing execs @#$ and doesnt relate at all to how much power your motor draws or could produce (unless stuck by lightning).

We had an amusing thread about that exact topic here a couple of months back -- search for "Lies, damn lies, and horsepower ratings."

To confuse matters, good quality Western and Japanese motors (Baldor, Mitsubishi, ...) quote the real horsepower rating, usually with a very conservative service factor...

pgmrdan
10-30-2009, 01:32 PM
I'm looking at the Ingersoll Rand air compressors in the Tractor Supply Co. catalog. TSC has a disclaimer that the ratings of the IR and CH compressors are those stated by the manufacturers.

Is it safe to assume that the ratings claimed by IR for their products should be dead-on accurate compared to the claims of Craftsman/Sears products?

I know my little Porter Cable General Electric compressor motor was claimed to be waaaaaaaaay more than it possibly could have been. (There was a class action suit over it.) I'm hoping IR is honest with their ratings.

Thanks,
Dan

Black_Moons
10-30-2009, 01:41 PM
Yea, with compressors, look for the CFM@90psi+ rating. its the only one the marketing department isent allowed to ruin/fiddle/cheat. (AFAIK anyway)
Of course, some compressors are rated CFM@40psi, and on compressors thats higher then the CFM@90 psi

6CFM = 1.5hp 120v 15A
12cfm = 3hp 240V 10~15A
16~18cfm = 5hp 240v 20~25A
seems to be the 'accurate' translation of CFM to motor hp/power consumption.
Also, electric motors only draw (additional over the small idle current) when loaded by the compressor, ie the wattage the motor uses is directly linked to how hard your compressor is working. a smaller pully on the motor will reduce current draw. (less air being compressed) so even if you have a 12cfm compressor with a 5hp motor, it still only draws 10~15A at 240v.

gnm109
10-30-2009, 01:42 PM
If you want to operate an outside sandblast or inside bead blast cabinet at any point, you will be needing at least 20 SCFM. Anything less and the unit won't cycle, it will just run all of the time and probably fall behind.

Lowes, Home Depot and the like don't have units that are very notable. I bought mine from a specialty store that only sells commercial units. I have and 80 gallon vertical with a real 5 hp Canadian motor. It's single phase and pulls 23 amps on 240 VAC. It's been running for close to fifteen years now. I operate my air tools, bead blaster and so forth with no problems. I just blow it down to get the moisture out about once a week and change the oil twice a year.

By the way, when you buy, look for one that has a certified tank. The American Society of Mechanical Engineers (ASME) certifies tanks that are built to their specifications and the manufacturers obtain a certification plate from them that is welded onto the tank at the factory. My tank is ASME certified. It's the equivalent of getting UL certification only on a pressure vessel. You will pay a little more but it's worth it.

I went through several small Sears compressors and two 60 gallon ones before I bit the buillet. You can never have enough shop air.

.

lazlo
10-30-2009, 02:00 PM
I'm looking at the Ingersoll Rand air compressors in the Tractor Supply Co. catalog. TSC has a disclaimer that the ratings of the IR and CH compressors are those stated by the manufacturers.

Is it safe to assume that the ratings claimed by IR for their products should be dead-on accurate compared to the claims of Craftsman/Sears products

Dan, MickeyD and I have the 3 HP, 220V IR compressor from TSC. See my comments/experience with it earlier in the thread.

It's a Chinese motor with an Indian compressor, so yes, the HP ratings are bogus.

radkins
10-30-2009, 02:29 PM
I don't really run out of air. I can run my die grinders...or other vane driven air motors wide open and the pressure rarely drops below 90 psi. The pump will keep up while the die grinder is running and will actually reach 135 again and shut off.


I will have to do a time test by charging up to 135 and bleed down to start pressure and time it with and without the 40 gallon tank. See if it really is adding a lot of recharge time.

I'll post the results after I do it.

That Emerson motor must be one inefficient lump if it is rated at 6.5 horse and only puts an actual 3.5 to the pulley. Maybe I should replace it with a 3.5 horse Baldor and save the power bill?

Cheers
Mac.


Since your compressor is keeping up OK then the extra 40 gallon tank is not really doing anything one way or the other and will not hurt anything, it just won't help either. As far as whether it takes longer to recharge with or with out it obviously if it has 66% more empty space to fill then it will take 66% longer to fill it, it's just simple laws of physics.


Also there is nothing wrong with your motor and it will handle that pump just fine the only thing wrong is the sales hype represented by that BS rating. 3 1/2 is all you need for that pump and if you replaced it with a motor with more HP and the same RPM you would not gain a thing except a motor that might last a little longer. Of course you could change the pulleys if you went to a bigger motor and run the pump faster to make more air but that would overspeed the pump and it wouldn't last long, not a good idea at all.

radkins
10-30-2009, 02:39 PM
I'm looking at the Ingersoll Rand air compressors in the Tractor Supply Co. catalog. TSC has a disclaimer that the ratings of the IR and CH compressors are those stated by the manufacturers.

Is it safe to assume that the ratings claimed by IR for their products should be dead-on accurate compared to the claims of Craftsman/Sears products?



They are doing that for more than just the motor HP ratings and no, IR can not be considered "dead on accurate"! TSC and Northern has one IR 5 HP (probably accurate HP) model that claims 18.6 CFM for a 5 HP SINGLE stage compressor, that's nonsense and that kind of performance for only 5 HP (even if it is really 5 HP) and a single stage pump is just simply out of line- 14 CFM would be much closer, maybe 15 CFM but I doubt it.

Falcon67
10-30-2009, 02:44 PM
Originally Posted by motorcyclemac
I have a 6.5 horse 'Husky' with a cast pump and Emerson motor mounted on top of a 60 gallon tank.

My 25 gallon Porter-Cable portable is a "6.5 HP" unit - not. It'd pull 44A at 110V. I don't think so. The motor is a really a 15A @ 115V 1.5HP unit. (pulls 14.4 running) Your Husky is the same unit as my CH except for color (same as the black Sears 60 G unit too) and it likely has a 3.2 HP motor on it. Check the label. It'll draw about 11 amps at 220V. Have not put the amp meter on this one yet.

I drain my big tank "sometimes" and under full pressure. I need to run a hose outside the shop to blow that junk in the alley. I modified the drain valve to use a ball valve and just crack it off once in a while.

Fill time - the 60 gallon takes mucho longer to fill than the 25 gallon unit, so if you run a 40 in tandem with the 60, I'd bet it takes 30% longer or so to hit the shutoff pressure. Mine runs from 85 to 125 psi.

PTSideshow
10-30-2009, 03:25 PM
Single Stage and Two Stage Reciprocating Pumps

Reciprocating (Piston) Compressors can be widely found in two primary configurations; Single Stage and Two Stage.

Single stage air compressors work by drawing air in and subsequently compressing the air to its final pressure in single piston stroke. Single stage air compressors can attain pressures of up to 150 PSI. Typically, a single stage pump will have a higher CFM(Cubic Feet per Minute) rating than a two stage pump because every cylinder is drawing in air and compressing it with air during every rotation.

Two stage air compressors work in a very similar manner with the primary difference being that they compress the air in 2 steps or stages. During the first step or stage, air is drawn in and compressed to an intermediate pressure. After being compressed in the first stage, the air is piped, usually through an intercooler where the air is allowed to cool, to be compressed in the final or second stage. Two stage compressors are normally good for pressures up to 200psi. Two stage pumps are more efficient at higher pressures because the air is cooled between the stages.

DCFM, SCFM and ACFM

Displaced CFM (DCFM) is a mathematical formula that calculates the bore, stroke and rpm into a CFM figure(Bore x stroke x rpm/2200=DCFM). This figure will always be the highest CFM because this formula does not take into account variables like temperature, atmospheric pressure, humidity, friction and heat dissipation.

Another CFM term often used is Standard CFM (SCFM). It defined as the measured flow of free air and converted to a standard set of reference conditions (14.5 PSIA, 68 Degrees F, and 0% relative humidity).

Yet another CFM term is Actual CFM (ACFM). AFCM can be determined in a number of different ways. The most common methods include measuring the volume of air that is moved through an orphic plate or measuring pump up times on large compressor tanks and running through a simple calculation. This CFM number takes in effect all the variables and will give the true output of the pump at the current working conditions (i.e. temperature, altitude, humidity, ).

Often times, CFM numbers are also shown at various pressures. These numbers can be very useful to help determine if a compressor produces enough CFM for the desired application, but can be confusing when comparing differing pressures or volumes or different compressors.

The best way of comparing compressors is through SCFM. Since all the measurements are calculated back to a set of reference standard conditions, it levels the playing field among the multitude of different manufacturers.

Electric Motors and Horsepower

Compressors are often rated by Horsepower(HP). As simple as this sounds, there are different variations of HP. Some compressor manufacturers rate their air compressors by peak horsepower, also known as brake horsepower. Peak horsepower is the maximum output that a motor can produce while the motor has the start windings engaged. Peak HP can be as much as 5-7 times the rated or running HP. Under normal operating conditions, the start windings are only engaged for a small fraction of a second. Therefore, using peak horsepower as a comparison tool can be somewhat misleading since under normal operating conditions the motor only develops this horsepower during startup. If a motor drive system causes the start winding to remain engaged for a long period of time, the motor will either overheat if it has thermal protection or fail prematurely.

Most electric motor manufacturers rate their motors by the horsepower developed after the motor has come up to its designed operating rpms and disengaged the start windings. This is often referred to as running or rated horsepower and is a true indication of the HP a motor can sustain over a long period of time.

Some other factors to consider when looking at motors is Duty Cycle and Service Factor. Duty cycle is normally rated as either intermittent or continuous and is defined as the time rating under full load. In other words can the motor run at full load horsepower continuously or only intermittently. The other of the two noteworthy factors is the Service Factor (S.F.) rating of the motor. It is defined as the percentage of rated horsepower at which the motor can safely operate (i.e. 1.15 SF = 115% of rated HP). Higher service factors allow motors to handle more varied conditions without causing motor overheating or premature motor failure. Examples that could cause a motor to run within its Service Factor could be caused by low voltage, higher ambient temperatures, higher startup load etc.

Note: Many companies are now eliminating the peak HP reference and instead using SCFM as a more accurate performance indicator.

The questions that need to be answered are:

1.) What is the maximum required operating pressure?

This will determine if a Single Stage or Two Stage compressor will be needed

2.) What is the maximum required CFM usage?

Add up all of the air tools that are to be used at the same time. When looking at the compressor, add approximately 30% to the determined CFM number. This will allow for a reasonable buffer against unknown or uncommon compressor usage.

Do not simply add up all of the air tools that will be used throughout the work day since this will produce an inflated CFM number and require the purchase of an overly large compressor.

3.) Does the machine need to be portable or stationary?

Determine whether or not the unit will need to be moved around your facility or work site regularly or if it will be a stationary unit. This will aid in determining other factors such as size and weight. Higher pressures and volumes will require the unit to be larger in size and heavier in weight since horsepower requirements, pumping systems, chassis construction, electrical components, etc... will have to be larger to accommodate these increases.

4.) What type of drive system is needed? Electric Motor or Gasoline Engine?

Knowing the environment that the compressor is to be used in will determine what type of drive system the machine will need. If there is always electrical power available, then the drive system should be an electric motor since they are significantly less expensive to buy and run and require less overall maintenance. If electrical power is not always available then the convenience of a gasoline engine driven compressor will be the way to go. They offer the best in portability and work area flexibility.

5.) What receiver tank size will be needed?

The size of the compressor tank, usually measured in gallons, should be determined by the overall type of usage. If the usage is in short quick concentrated bursts, such as an air nailer, then a small tank size can be used. If the unit is to sustain long periods of usage, such as a board sander or impact wrench, a larger tank size will be necessary.
1.) What is the maximum required operating pressure?

This will determine if a Single Stage or Two Stage compressor will be needed

2.) What is the maximum required CFM usage?

Add up all of the air tools that are to be used at the same time. When looking at the compressor, add approximately 30% to the determined CFM number. This will allow for a reasonable buffer against unknown or uncommon compressor usage.

Do not simply add up all of the air tools that will be used throughout the work day since this will produce an inflated CFM number and require the purchase of an overly large compressor.

3.) Does the machine need to be portable or stationary?

Determine whether or not the unit will need to be moved around your facility or work site regularly or if it will be a stationary unit. This will aid in determining other factors such as size and weight. Higher pressures and volumes will require the unit to be larger in size and heavier in weight since horsepower requirements, pumping systems, chassis construction, electrical components, etc... will have to be larger to accommodate these increases.

4.) What type of drive system is needed? Electric Motor or Gasoline Engine?

Knowing the environment that the compressor is to be used in will determine what type of drive system the machine will need. If there is always electrical power available, then the drive system should be an electric motor since they are significantly less expensive to buy and run and require less overall maintenance. If electrical power is not always available then the convenience of a gasoline engine driven compressor will be the way to go. They offer the best in portability and work area flexibility.

5.) What receiver tank size will be needed?

The size of the compressor tank, usually measured in gallons, should be determined by the overall type of usage. If the usage is in short quick concentrated bursts, such as an air nailer, then a small tank size can be used. If the unit is to sustain long periods of usage, such as a board sander or impact wrench, a larger tank size will be necessary.

The above was quoted from this web site This is the no BS what you need to ask yourself. No hype and no BS just the questions.

How to choose the right air compressor (http://www.jennycompressor.com/howtochoose.html)

You can read the complete write up at the above link
Great web site full of information as a previous poster said, The only bad thing I can say about the site is you have to call and ask for a dealer near your zip code

I will say that I'm thinking of hunting up a dealer and kicking the tires on one.
3hp 230v 1 175 psi 80 gallon two stage Vertical 10.7 CFM $2,294
5hp 230v 1 175 psi 80 gallon two stage Vertical 15.2 CFM $2,379
They are low rpm pump and motors. and with all the other stuff on them. It should have enough guts and glory for my needs in to the future!
:D

cuemaker
10-30-2009, 03:45 PM
I am confused by something and dont think its been explained unless I missed it...

Why would a 1.5hp motor have less cfm than a 5hp motor? As I think of it, it takes the same amount of oooffa to turn the fly wheel to turn the pumps etc...

Now I understand that in building pressure up... you need a bigger motor to have more power to get the air in,,, but in running at say 90 psi why is a 5hp motor gonna give more cfm than a 1.5hp motor turning at the same RPM???

If the flywheel is moving and its making the pistons works...should produce the same CFM no matter the HP??

PTSideshow
10-30-2009, 05:20 PM
Displaced CFM (DCFM) is a mathematical formula that calculates the bore, stroke and rpm into a CFM figure(Bore x stroke x rpm/2200=DCFM). This figure will always be the highest CFM because this formula does not take into account variables like temperature, atmospheric pressure, humidity, friction and heat dissipation

It won't as the smaller hp are turning at higher rpm's than a higher hp motor. It has more to do with the pump bore and stroke as in the above.
If you go to the site in my post before yours they explain everything you probably would need to know
:D

cuemaker
10-30-2009, 05:30 PM
I did read it... umm most of it...

So I am basically right... as long as the pumps are pumping and the rpm is the same, the running cfm will be the same no matter the HP...whether it be a 1hp or a 5hp...provided they all can turn the pump.

So then, when people keep on saying that a 5hp motor produces more CFM its because its turning a bigger pump....or at least has the ability to turn a bigger pump...

hardtail
10-30-2009, 05:37 PM
Cuemaker think of the higher cfm as resistance to load, a 1.5 hp motor likely wouldn't even be able to apply the sufficient starting torque to come up to speed even with unloaders on the pump much less actually drive the pump at the motors required rpm.

Arcane
10-30-2009, 06:14 PM
One thing about having a larger than usual receiver volume is the reduced number of starts necessary to move the same amount of air. Wouldn't this extend the life of the centrifugal switch a certain amount?

radkins
10-30-2009, 08:22 PM
One thing about having a larger than usual receiver volume is the reduced number of starts necessary to move the same amount of air. Wouldn't this extend the life of the centrifugal switch a certain amount?


Yes it would and that's one of the things I was talking about when I said that a bigger tank will usually mean less wear and tear on a compressor. When the compressor has to restart it has to do so under a load so that means a high torque start for the motor=more wear and tear and momentary high AMP draw which means higher power consumption. These effects are not huge however and the difference between a 60 gallon tank and an 80 gallon tank will be small, almost insignificant when considered in the short term but over the life of the compressor it can add up. All things considered on a compressor of about 14 CFM or so and up to about 24 CFM an 80 gallon tank would be about right, from around 9 CFM up to about 12 or 13 CFM a 60 gallon would be a good choice but between 12 to 16 CFM it really would not make much difference one way or the other. Having too much tank requires the motor and pump to run too long during the recharge cycle which is not good for the pump due to heat, also a hot pump will not compress as efficiently which will extend run times even longer.


People tend to look at two things when they see a compressor, the HP and the tank but what really matters is invisible and that is the CFM! Since most guys want to think that bigger is better then a bigger tank and more power means a better compressor right? Not exactly because no matter how big a tank is the only air that is going to come out of it is the air that the pump puts in it and HP over what is required to turn the pump at the proper speed will not increase performance. A bigger tank will only change the cycle rate and if the operator is running out of air with a 60 gallon tank he will still run out of air with the 80 gallon tank but it will take a few seconds longer, then any and all extra time that is gained from the extra 20 gallons will be lost to the extra recharge time. There's no way around it because it is simple laws of physics so the time you can use a compressor during any given work period will be the same regardless of the size of the tank. I have had people try to argue that the extra storage in an 80 gallon tank extended their run time by minutes with little or no increase in recharge time, I would like to see someone explain the physics behind that one!:rolleyes: If a 60 gallon tank is running out of air at an annoying rate then how long would it take to run out of air with a 20 gallon tank? That's the difference between a 60 and an 80 and even that tiny bit is still lost to the extra recharge time, still some guys refer to compressors as 60 gallon or 80 gallon and will buy the biggest tank in the store without even looking at the CFM! If the CFM is low then the compressor is small and more tank capacity does not make it any bigger!

ulav8r
10-31-2009, 12:00 PM
Quote {So then, when people keep on saying that a 5hp motor produces more CFM its because its turning a bigger pump....or at least has the ability to turn a bigger pump...}

A compressor usually has the motor sized to match the pump. A larger motor is paired with a larger displacement pump. Occasionally the same pump will be available with different size motors. In that situation the smaller motor will be turning the pump slower and putting out less CFM that the larger motor that can turn the pump faster.

radkins
10-31-2009, 12:44 PM
Occasionally the same pump will be available with different size motors. In that situation the smaller motor will be turning the pump slower and putting out less CFM that the larger motor that can turn the pump faster.



That is true but more so on the larger industrial type pumps than on the smaller more common consumer type pumps but, as you point out, even they do this sometimes however it will be within a much smaller range. The problem with the more common home shop type pumps is the splash type oiling system which will not work properly at lower speeds and since the pumps tend to be of a smaller displacement in the first place most of them are already pushed to about their practical limit of about 1000 RPM. This only becomes important when someone decides to add a bigger motor and drive the pump faster by changing the drive ratio which can, and usually does, lead to overheating and shortened pump life. Occasionally someone may try to drive a larger pump with less power and reduce the pump speed to make it work but if it is splash lubricated that could present a problem if it is turned too slow. Either case can work but on the common consumer type pumps it can only be done within a narrow range.

MickeyD
10-31-2009, 11:17 PM
My twoish year old 60 gallon 3HP Ingersoll compressor is on pump number three now and motor number two is sitting on the floor waiting to be installed tomorrow morning. According to the Ingersoll repair technician that I spoke with confirmed that their small compressors use pumps made in India and the motor on mine was made in Mexico. My advise is that if you are thinking about buying a 60 gallon Ingersoll 3 or 5 HP compressor, just buy the cheapest Lowes/Homedepot/KMart similar unit and save the extra $200 or so dollars that you are going to spend for Ingersoll "quality".

radkins
11-01-2009, 09:44 AM
save the extra $200 or so dollars that you are going to spend for Ingersoll "quality".


That is exactly what I was talking about when I said earlier that no, you can't believe IR is dead on accurate-neither in performance nor quality claims! That 5 HP single stage model with the 18+ CFM rating I mentioned has become notorious for burning out motors and it's because they attempted to cheap out on the motor and still try to drive that pump to a higher CFM than the motor torque could handle.

PTSideshow
11-01-2009, 10:25 AM
Lowes/Homedepot/KMart similar unit the ones that say made in the USA are really assembled in the states. the parts can be fore anywhere. Kobalt, Husky and others are assembled by the same company. The small hardware might be and the ASME stamped tanks are made in the USA.

lazlo
11-01-2009, 10:31 AM
the ones that say made in the USA are really assembled in the states. the parts can be fore anywhere.

In order to be marked Made in USA, all the parts have to be made in the US. AFAIK, only Quincy and Champion are Made in USA anymore.

Where things get tricky is some of the tanks are Made in USA, so the tanks are marked as such, but the compressor head and motor are not, so the manufacturer doesn't claim the whole unit is. But you walk into the store and see that big American flag on the tank...

Basically, if you're buying a compressor at a consumer outlet (Sears, TSC, Home Depot, Lowes) or paying less than $1500 for an air compressor, it's made in China.

lazlo
11-01-2009, 01:18 PM
I just got back from Home Depot (still looking for bentonite clay :( ), and the Husky Pro series compressors are not marked Made in USA, even though the compressor head on a couple of the models is cast "Made in USA."

The lower-end models have Chinese Emerson motors. The more expensive models have "Assembled in Mexico" motors.

To be honest, the compressor heads all looked like sh!t, including the one's cast "Made in USA".