{"id":91498,"date":"2023-07-21T07:46:41","date_gmt":"2023-07-21T14:46:41","guid":{"rendered":"https:\/\/www.racingjunk.com\/news\/?p=91498"},"modified":"2023-07-21T07:46:42","modified_gmt":"2023-07-21T14:46:42","slug":"compressed-air-the-shop-staple-part-2","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/compressed-air-the-shop-staple-part-2\/","title":{"rendered":"Compressed Air \u2013 The Shop Staple Part 2"},"content":{"rendered":"\n

In Part 2 of Wayne Scraba’s series on compressed air, he looks at the practical aspects — power needs and power delivery.<\/h2>\n\n\n\n

In our last segment <\/a>we examined the basics of shop air compressors. If you spin your browser back to that article, you\u2019ll recall we looked at tank configurations, sizes and compressor types. <\/p>\n\n\n\n

This time around, we\u2019ll zoom in on the power needs of the compressor along with the air quantity needs of various power tools. You might be surprised to find some seemingly innocent looking tools have a voracious appetite for compressed air. But other seemingly huge air users are actually quite frugal. <\/p>\n\n\n\n

Power
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There are lots of ways to rate an air compressor. Some folks make decisions based upon the pump output PSI while others rate the compressor by electric motor horsepower. The best compressor performance gauge is the output CFM at a given PSI. The rate at which a compressor can deliver a volume of air is noted in cubic feet per minute (CFM). Because atmospheric pressure plays a role in how fast air moves into the cylinder, CFM varies with atmospheric pressure. It also varies with the temperature and humidity of the air. To create a standard, manufacturers calculate standard cubic feet per minute (SCFM) as CFM at sea level with 68 degrees F air at 36% relative humidity. SCFM ratings are given at a specific pressure, for example, 20 SCFM at 100 psi. If you reduce pressure, SCFM goes up, and vice versa.

You also may run across a rating called \u201cDisplacement CFM\u201d. This figure is the product of cylinder displacement and motor rpm. In comparison with SCFM, it provides an index of compressor pump efficiency. The CFM and PSI ratings are important because they indicate the tools a specific compressor can drive. When choosing a compressor, make sure it can supply the amount of air and the pressure your tools need. The bottom line here is to select an air compressor that exceeds the CFM of your most powerful air tool.

Just how much air does a given pneumatic tool require? Check out the following chart. Keep in mind this is only a general guide, since some brands and configurations of air tools use more or less air:
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Too<\/strong>l<\/td>CFM<\/strong><\/td>PSI<\/strong><\/td><\/tr>
Upholstery Stapler<\/td>2.0<\/td>30<\/td><\/tr>
Ratchet 1\/4″<\/td>3.0<\/td>90<\/td><\/tr>
Air Hammer<\/td>4.0<\/td>90<\/td><\/tr>
Die Grinder 1\/4″<\/td>4.0<\/td>90<\/td><\/tr>
Drill 3\/8″<\/td>4.0<\/td>90<\/td><\/tr>
Drill 1\/2″<\/td>4.0<\/td>90<\/td><\/tr>
Impact Driver 1\/2″<\/td>4.0<\/td>90<\/td><\/tr>
Ratchet 3\/8″<\/td>4.0<\/td>90<\/td><\/tr>
Spray Gun, Commercial<\/td>4.0 – 7.0<\/td>30-70<\/td><\/tr>
Jitterbug Sander<\/td>6.0<\/td>90 <\/td><\/tr>
Board Sander<\/td>7.0<\/td>90<\/td><\/tr>
Impact Driver 3\/4″<\/td>7.5<\/td>90<\/td><\/tr>
High Speed Grinder<\/td>8.0<\/td>90 <\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n




Electrical Requirements
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The electric motors found on air compressors range from simple 110-volt 1\/2 HP models all the way up to giant three-phase, 25+ HP 220-240-volt monsters. The electrical service available to your house or shop dictates the largest compressor you can install (we\u2019re talking 220-240 volt models here). The electricity supplied to the majority of residential properties consists of a single phase, or voltage signal. But the electricity used by heavy industries is generally three-phase power. Few, if any, residences have three-phase electrical capability (and neither do some commercial buildings). There are converters available that allow you to use a three-phase motor in a building that is wired for single phase, but if buying a new compressor, it\u2019s simply more practical to begin with a single phase model.

When shopping for a compressor, keep an eye out for the amperage rating of the electrical motor. Electrical service is measured in amps with the standards being 100, 150 and 200 for a typical residence (usually, the older the residence, the smaller the electrical service). Amperage is like the size of the water pipe that feeds the residence \u2013 the bigger the pipe the more water that can be delivered to the house. So far so good, but what about the electrical motor? All compressor motors should have a tag that indicates the amperage of the motor. The 5 HP, 230-volt Baldor motor on the Devair compressor shown in the accompany photos has a 23 amp rating. To accommodate the compressor motor, a dedicated 30-amp circuit is used in the shop panel. If you do the math, a residence that has a 100-amp service will be hard pressed to give up 30 amps just for an air compressor. You can see the need for 200-amp service in a situation such as this. As the electric motor size (HP) goes up, so does the amperage requirement. In other words, it is definitely possible to overwhelm the electrical service in your workshop with a monster compressor. Finally, remember that there is only so much one can accomplish with a simple 110-volt air compressor. Most hobby compressors are really overrated (for marketing purposes) and operate on a normal 15-amp 110-volt circuit that is only capable of running about 2 real HP or less.

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A final consideration when purchasing an air compressor is service. There are dozens, if not hundreds of air compressors on the market today. Some are made in North America. Plenty of others aren\u2019t. Some manufacturers have credible parts and service \u201cchains\u201d while others have zero maintenance or service items available. What you have to consider when buying a large item such as a shop compressor is if the manufacturer will be around long enough to supply parts if they are ever necessary. Otherwise, the air compressor you purchase will have a true value of $1.50 per pound (or whatever the going rate for scrap metal is today). When it comes to air compressors, you definitely get what you pay for. For a closer look at air compressors as well as important compressor accessories, check out the accompanying photos.

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