Air compressor buyer’s guide: what you need to know

An air compressor is a versatile tool that performs a variety of tasks when attached to air tools, also known as pneumatic tools. Air tools have several advantages over electric power tools: more torque and power, more durability thanks to fewer moving parts, and they’re easy to use.

You can use a compressor for maintenance around the house, repair jobs in the garage, construction on the job site, or industrial work in the shop. Nail guns, hammers, spray guns, wrenches, drills, sprayers, sanders, saws and tyre inflators all run on air.

Ask these questions first

• Which tools do you want the compressor to operate?
• Will you be working in confined or unventilated areas?
• Does the machine need to move around the site, or does it stay put?

The four numbers that matter

• PSI — pounds per square inch. The air pressure the compressor delivers. Higher PSI means air can be compressed further, so a larger volume is stored in the same tank.
• CFM — cubic feet per minute. The volume of air the compressor pumps in a minute at a stated working pressure. Higher CFM means more air, and more capable tools.
• HP — horsepower. The power the motor produces. Higher horsepower produces greater PSI and carries a heavier workload.
• Tank size — bigger tanks and stronger motors hold higher pressure for longer, so tools don’t starve mid-job.

To size it properly, take the tool that needs the highest CFM at the highest PSI, then choose a compressor that comfortably exceeds both. Sizing to the biggest tool, not the average one, is what stops a compressor cycling itself to death.

Styles, and what they suit

• Twin-stack — maximum portability with a low profile for stability on uneven ground. Suits roofing, remodelling, car maintenance and clean-up.
• Pancake — light, portable, and forgiving of tight spaces. Suits building, inflation, crafts and outdoor clean-up.
• Wheelbarrow — easy manoeuvring on building and maintenance sites. Often petrol-driven, so keep it ventilated.
• Stationary receiver-mounted — for a workshop or production floor where air demand is continuous.

For casual work such as tyre inflation, nailing, stapling, upholstery or airbrushing, a highly portable machine is enough. For auto repair, removing lug nuts, sanding, drilling or spray guns, look for a receiver over 5 gallons — and in a production setting, considerably more.

Features worth paying for

• Belt-drive, oil-lubricated pump with a cast-iron cylinder — runs at lower rpm, extending life and reducing noise.
• Well-protected, conveniently located control panel and gauges.
• A heavy-duty motor with manual reset overload protection.
• Electric start with built-in pressure release, so start-up doesn’t trip circuits.
• Two air outlets for dual-tool operation.
• Ball-valve tank drain — a quarter turn and it’s drained.

Running it properly

• Check the oil level so the pump is properly lubricated.
• Plug into a correctly grounded three-pin outlet, switch on the pressure switch and close the tank drain valve.
• Set the pressure for the tool and the job, and never exceed the tool’s rating.
• When finished, shut off the motor, unplug, close the regulator, bleed the hose and remove the tool.
• Open the drain cock to release accumulated moisture, and leave it open until next use.

Maintenance and safety

• Read the manufacturer’s manual and follow its safety and operating rules.
• Wear safety glasses and hearing protection.
• Check the machine regularly for visible problems, and confirm the pressure safety-valve ring operates.
• Use regulated air, and never more pressure than the job needs.
• Keep the air filter clean — more often in a dusty environment.
• Drain the tank at the end of every day. Moisture left in a receiver causes rust and weakens the tank.

Energy-efficient motors cut energy use by at least 12%, and the most efficient are fitted with controllers and variable-speed drives that match output to the work being done. Over a production year, that difference is not small.

If you have technical queries or want help choosing the right machine, talk to the Airpower team directly on 051 373 937.