The 20 Gallon Air Compressor Portable Compact Little Powerhouse

A 20 gallon air compressor is a single stage compressor with a maximum 135 PSI. Designed as small single stage compressor for home and light commercial use.  Most are generally direct drive electric motor designs and are maintainence oil free units. Electric motors and gas combustion engines are most commonly used to drive air compressor pumps. The choice is dictated by the location of where the pump will be used the most. Electric pumps can be used with diesel or gas generators as another option.

The choice again is cost and only one piece of equipment or a generator and a pump combination. An electric 20 gallon air compressor operates on a standard 15 amp 120 volt AC circuit. Most are direct drive with some models available with motor and belt drives. Aluminum cast compressor pumps are more common because of cost compared to cast iron which costs more.

Solid cast-iron units are up to 35 percent quieter than aluminum units with cast-iron cylinder sleeves, and are dramatically quieter than direct-drive aluminum compressors. So if quiet and longevity are importnat to you a belt driven cast iron compressor will be the best choice.

Oil Less Or Oil Lubricated

Oiless models are often the choice by users where painting a fine finish is essential such as woodworking shops or for the serious hobbyist.  These units are direct drive with permantely lubricated bearings.  Oil leakage can be filtered out if you prefer an oil lubed compressor.

Just be aware that in a closed in space in close proximity to your work area a direct drive 20 gallon air compressor self lubricating aluminum compressor is dramatically louder than an oil lubed belt cast iron drive compressor. Maintainence free oil less direct drive compressors have a much shorter life than belt driven oil lubed units.

This model the Campbell Hausfeld 20 Gallon Air Compressor is a cast iron, oil lube belt drive unit. Delivers 5.58 CFM at 90 PSI. Operates with a twin cylinder pump.

Single Or Two Stage

Most pumps are either single-stage or two-stage. The difference refers to the number of times intake air is compressed in a pump. A single stage compressor compresses intake air one time before sending the air into a storage tank. Single-stage air compressors can have one, two, or four cylinders, but the air is only compressed once.

Two-stage air compressors compress air twice before sending it into a storage tank. A two-stage compressor has a minimum of two cylinders: a low-pressure cylinder (largest) and a high -pressure cylinder (smallest). Air is compressed once in the large cylinder and then sent through an air cooling tube, which reduces discharge air temperatures.

The Duty Cycle

In the information pack with your compressor look for "duty cycle". The duty cycle tells you how many minutes the compressor should run in any ten minute period, expressed as a %, for instance a compressor rated at a 50% duty cylce should run for only 5 minutes out of every ten minutes.

If the compressor runs longer than the duty cycle the pump will get hot which shortens service life. Depnding upon the compressor duty cycles can be continuos usually in heavy duty industrial compressors. 

Match The Need To The Tasks  At Hand

You want an air compressor that exceeds the CFM of your most powerful air tool. If the flow isn’t strong enough, the air tool simply won’t perform properly. The extra PSI pressure does little to improve the machine’s performance.

Required Air Flow For Popular Air Tools (Rated in CFM)

Nailer 1-4
Spray Gun 2-4
Impact Wrench 2-5
Sandblaster 6-10
Sanders 6-13

Check the CFM rating of your air tools first and match the compressor to the tool air flow requirement and the legnth of time the unit will be running. A 20 gallon compressor (single stage) will handle most air tools listed above. Sanders and sandbalasting may require a two stage unit. A 60 gallon air compressor would be ideal for more power aplications