Air Compressor Class

Air compressors get confusing because they have two pressures, one airflow number, a regulator, a tank that fills and empties, and tools that can use air faster than the pump makes it.

The 30-second version: Tank PSI tells you stored pressure. Regulated outlet PSI is what you send to the tool. SCFM tells you how much air the compressor can deliver at a stated pressure. A tool can need acceptable PSI and still outrun a small compressor because it needs more airflow.

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If you are starting from scratch, compare whether the kit includes a hose and fittings. A compressor alone may not be enough to connect a tool.

Browse portable air-compressor kits

This class uses the DEWALT DWFP55126 manual as a worked example. That model has a 6-gallon tank, approximate 135 PSI cut-in pressure, 165 PSI cut-out pressure and 2.6 SCFM at 90 PSI. It uses 1/4-inch industrial quick connects.

Lesson 1: Tank pressure is not tool pressure

The tank gauge shows stored air. The outlet gauge shows the pressure available after the regulator. On the DWFP55126, DEWALT says the outlet pressure is controlled by the regulator and is always less than or equal to tank pressure.

See the regulator and gauge guide.

Lesson 2: PSI and SCFM answer different questions

PSI is pressure. SCFM is air delivery. A nailer may use short bursts and let a small compressor recover. A continuous-use tool can demand more SCFM than the same compressor can make, even when the PSI setting looks fine.

Read PSI vs. SCFM before choosing a compressor for a tool.

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Useful starter kits often include a tire chuck, blow gun and fittings, but verify the coupler style.

See basic air-compressor accessory kits

Lesson 3: The tank collects water

Compressed air cools in the tank and moisture condenses. DEWALT says to drain condensation at the end of each use and warns that trapped water can corrode and weaken the tank.

See how and why to drain the tank.

Lesson 4: More electrical cord is usually not the best way to get more reach

For the DWFP55126, DEWALT limits extension cords to 50 feet and requires 14 AWG or larger. The manual actually recommends adding air hose rather than undersized electrical cord when you need more reach.

Use the extension-cord guide before plugging in a long lightweight cord.

Lesson 5: A compressor that runs often may be normal, but one that never stops is not

The motor is supposed to cycle between cut-in and cut-out pressure. If the tool uses air faster than the compressor replaces it, the motor will run frequently. If pressure climbs past normal cut-out until the safety valve opens, that is a service problem.

Work through the class by problem

Sources used for this answer

More project guides: Tools & Workshop.