Small Air Compressors for Workshops

Shop compressor selection often gets simplified to "calculate air demand, look up table for power." This thinking isn't wrong, but misses a few things that should be thought through during selection.

Workshop Setup

Small Compressor Installation

Single phase 220V or three phase 460V, this question comes before all technical parameters. Reason is simple: 3 hp is the upper limit single phase can drive. Going higher requires three phase power. Shops renting factory space especially need to watch this. Three phase power upgrade involves utility approval. Timeline and cost aren't small numbers.

3 hp equipment outputs 7 to 10 CFM. Intermittent pneumatic tool use, tire inflation, small area painting barely enough. Both piston and scroll tech routes available. Noise from 55 decibels to 68 decibels, difference mainly from compressor type not brand. Whole unit around 100 pounds, dimensions around 24×16×24 inches, two people can move it.

No three phase power but really need bigger volume, diesel driven portable compressor is one path. But noise, exhaust, fuel consumption are all issues. Fixed shops generally don't consider.

With 460V three phase, 5 hp to 20 hp range fully opens up.

5 hp is an interesting node. This power range has piston, scroll, and small screw three tech routes coexisting, each with fans. Piston is cheap and tough. Scroll is quiet and output is oil-free. Small screw is efficient and suits long runtime. Volume 14 to 19 CFM, pressure options 115 psi or 145 psi. Equipment length reaches around 32 inches, weight passes 180 pounds. Moving starts needing mechanical assistance.

Above 10 hp, screw gradually dominates. Not that piston and scroll can't be made this big. Under continuous operation, screw efficiency advantage is too obvious. 10 hp screw outputs 28 to 42 CFM. 15 hp around 53 CFM. 20 hp approaches 70 to 88 CFM.

Piston

Reciprocating Type

Scroll

Oil-Free Output

Screw

Rotary Efficiency

Bigger power machine always louder? Not necessarily.

3 hp piston at full load can hit 68 decibels. Higher than 20 hp screw's 66 decibels. Reciprocating compressor vibration and airflow pulsation are inherently more violent than rotary type. Sound enclosure can only suppress part of it. Scroll is the quiet choice across power ranges. 3 hp scroll can do 55 decibels. Close to normal conversation volume.

Care about noise, pick scroll or screw. Tight budget, go piston plus add sound insulation measures. Or just move compressor room outside the shop.

Main unit, air receiver, refrigerated dryer packaged in same frame. Installation just connects power and air outlet. Done. Saves trouble for sure. Premium is also for sure.

Package Unit

Integrated System

Components

Separate Setup

Air receiver capacity rough estimate is power times 6 to 7 gallons: 3 hp with 13 to 26 gallons, 10 hp with 40 to 80 gallons, 20 hp with 80 to 130 gallons. Refrigerated dryer processing capacity buy one size bigger than compressor discharge. Humid weather and high load conditions, margin helps.

After totaling all pneumatic equipment consumption, add 20-30% margin then select model. This experience is widely circulated. Margin covers pipe leakage, peak demand when multiple equipment starts simultaneously, and room for adding tools later.

Too small is worse than too big. Compressor long-term full load operation, life takes a hit, electricity goes up, noise can't be suppressed either. Selecting a bit bigger, besides paying more upfront, no big downside. Talk about screw machines having oil circulation issues at long-term low load exists, but load rate above 50-60% generally no need to worry.