SCFM= Too low to run standard air tools?

SCFM= Too low to run standard air tools?

by Jason Moore
(Grovetown, GA, USA)

My Compressor

My wife just bought me a craftsman vertical air compressor.

Being new and unfamiliar to air compressors we thought that the bigger tank allowed for a wider range of tools to be used efficiently and effectively.

To my dismay, and my wifes, we found out that our SCFM on our Craftsman compressor is only rated at 4.3 SCFM at 40psi and 3.3 SCFM at 90psi.

Our impact wrench, from Craftsman, uses 4.8 SCFM and my impact gun likewise uses far more SCFM than is rated for our compressor.

So I looked around and found that most air tools from almost every maker exceeds the ratings for my compressor. Is the do-it-yourselfer forced to pay $400-$1000 for a compressor that runs at least 10 SCFM to ensure that a variety of tools have enough air to run properly??

Thanks,
Jason Moore

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SCFM= Too low to run standard air tools?

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Aug 11, 2008

Many good points about compressors...
by: Anonymous

However, I would like to point out that a 120VAC outlet @ 15 amps can deliver 1800 Watts of power. That is equal to 2.38 horsepower (a bit more than 1/2). This isn't to say that the motor on the compressor can produce as much mechanical HP as it says (the words "peak" or "peak-peak" indicates that it is much less than the true value of HP). The best thing to do is to look at the current the motor draws and then multiply it by the line voltage. This will give you the VA (volt-amps) that the motor consumes. The typical single phase motor has a PF (power factor) of 0.80 which, when multiplied by VA, gives you the wattage of the motor. The wattage divided by 756 (watts/HP) will give you the actual HP.

Example: My small compressor is a 1.6 HP, 33 gal 6.0 SCFM @ 90 psi model which I bought nearly 10 years ago. It does just fine on a dedicated 120 volt, 15 amp, single-phase outlet. The motor is rated at 12.5 amps.

12.5 amps * 120 volts = 1500 volt-amps
1500 VA * 0.8 = 1200 watts
1200 W/756 (W/HP) = 1.587 HP.

The label is accurate. This compressor is also more than adequate to run every air tool I own. If you need something bigger, you probably ought to think about opening up a shop.

Aug 07, 2008

Right but wrong
by: Anonymous

The above comments are correct.

However you are not running an impact wrench continually. Nor do you run most air driven tools that the average homeowner or DIY will use. If you go buy an air powered grinder or other tool that will run for several minutes then you may have a problem. Otherwise enjoy the tools. You may really want to look into putting the compressor on a 20amp circuit if it is possible based on location.

Feb 23, 2008

Too little SCFM....another comment
by: Jim

Sorry but you will run out of power on most household circuits (15 amp)to ever even began to generate enough compressed air to supply even one air tool full time.

So go electric instead if you want all day running, or just use short bursts of compressed air for your air tool (nail gun) to do the job.

Jan 21, 2008

Too little SCFM....continued
by: Bill - Publisher

That's why at about 2 HP or greater you'll want to have a 240 VAC power supply, and why larger compressor installations use 460 or 575 VAC in multi phases.

So, and I know it's too long to make this a short answer :-), if you want to run your air tool continuously, you'll need a bigger compressor, and at least 240 VAC power.

Or, you can use your impact gun, air drill, air nailer or what have you for a bit, then put them down until your compressor recharges.

Remember, 90 PSI at high flow is exactly the same as 90 PSI at low flow. If your tool needs 90 PSI to run properly, and your compressor can only deliver that 90 PSI for a few seconds before the demand exceeds the supply, then you have to wait for the compressor to catch up.

Here are some tips on air tool usage. And if you are using your compressor a great deal, please don't forget about it's duty cycle.

Bill

Jan 21, 2008

Too little SCFM
by: Bill - Publisher

Hi Jason.....good questions and an issue that's relevant to many visitors here. Thanks for asking it.

One of my pet peeves is companies that rate the flow of air out of their compressors in SCFM. The S in SCFM standards for Standard, and a standard cubic foot of air is at 14.7 PSI, 68 deg. F and at sea level, hardly what is coming out of a compressor.

Many folks confuse pressure with flow. The fact that you purchased a larger compressor receiver with your unit is good. A larger reservoir of compressed air will allow longer periods between compressor kick in and cut out, this depending on the demands of the tool.

Your tool will have a demand of, say, 4 CFM @ 90 PSI. In order for this air tool to be used continuously, the compressor must be able to generate at least that much compressed air or, as you use the tool, the compressed air to the air tool will continue to dwindle well below the tool's MOP (minimum operating pressure) and ultimately to nothing.

Put the air tool down for a couple of minutes, and the compressor will continue to run until the receiver pressure reaches the cut out point, at which the compressor will stop.

One issue is I think that many of the DIY compressor manufacturers bank on the fact that home users generally don't need to run their air tools continuously and, in order to keep their compressors as competitively priced as possible, don't offer home compressors with the capacity to deliver compressed air in great quantities.

The more important issue is that most DIY's are going to plug their compressors into a 110 VAC socket.

When you plug in a compressor, you are, essentially, converting the available supply of electricity into compressed air through an electric motor. The motor will be big enough to run the compressor head and generate compressed air.

But, and it's a big but, 110 VAC through a 15 AMP circuit can only deliver about 1/2 HP of energy. A DIY compressor, regardless of what it says in the literature, and regardless of the rated HP of the motor, is limited by this fact. You cannot get enough electricity through a 110 VAC 15 AMP to power a bigger motor, therefore, your compressor discharge pressure and flow rate has a finite limit as well.

.....to be continued.

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Jan 21, 2008
Rating

Submitted by: Bill - Publisher

Title

Comment
Hi Jason.....good questions and an issue that's relevant to many visitors here. Thanks for asking it. One of my pet peeves is companies that rate the flow of air out of their compressors in SCFM. The S in SCFM standards for Standard, and a standard cubic foot of air is at 14.7 PSI, 68 deg. F and at sea level, hardly what is coming out of a compressor. Many folks confuse pressure with flow. The fact that you purchased a larger compressor receiver with your unit is good. A larger reservoir of compressed air will allow longer periods between compressor kick in and cut out, this depending on the demands of the tool. Your tool will have a demand of, say, 4 CFM @ 90 PSI. In order for this air tool to be used continuously, the compressor must be able to generate at least that much compressed air or, as you use the tool, the compressed air to the air tool will continue to dwindle well below the tool's MOP (minimum operating pressure) and ultimately to nothing. Put the air tool down for a couple of minutes, and the compressor will continue to run until the receiver pressure reaches the cut out point, at which the compressor will stop. One issue is I think that many of the DIY compressor manufacturers bank on the fact that home users generally don't need to run their air tools continuously and, in order to keep their compressors as competitively priced as possible, don't offer home compressors with the capacity to deliver compressed air in great quantities. The more important issue is that most DIY's are going to plug their compressors into a 110 VAC socket. When you plug in a compressor, you are, essentially, converting the available supply of electricity into compressed air through an electric motor. The motor will be big enough to run the compressor head and generate compressed air. But, and it's a big but, 110 VAC through a 15 AMP circuit can only deliver about 1/2 HP of energy. A DIY compressor, regardless of what it says in the literature, and regardless of the rated HP of the motor, is limited by this fact. You cannot get enough electricity through a 110 VAC 15 AMP to power a bigger motor, therefore, your compressor discharge pressure and flow rate has a finite limit as well. .....to be continued.

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SCFM= Too low to run standard air tools?

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SCFM= Too low to run standard air tools?