Two compressors of the same power can have very different data sheets. To compare them, you need to know what each line means, and above all which ones matter for your use. Let us take the data sheet of our S 110, an 11 kW screw compressor, as an example.
The data sheet, line by line
| Data sheet line | S 110 value | What it tells you |
|---|---|---|
| Power | 11 kW | The power of the electric motor. It gives an order of magnitude, not the amount of air produced |
| Pressure | 8, 10 or 13 bar, your choice | The maximum pressure the machine delivers. To be chosen according to the most demanding tool |
| Flow | 1.7 m³/min at 8 bar; 1.4 at 10 bar; 1.1 at 13 bar | The amount of air produced. This is the most important figure |
| Noise level | 68 to 72 ± 2 dB(A) | The measured noise, to be compared at the same measuring distance |
| Power supply | 380 V three-phase / 50 Hz | The electrical connection required |
| Connection | G 1/2" | The size of the air outlet, for sizing the connection |
| Dimensions | 1050 × 700 × 1000 mm (L × W × H) | The footprint, to be checked against access to the room |
| Weight | 210 kg | For handling and the floor |
| First service | 500 hours, then every 1,500 hours | The service interval to plan for |
| Oil | 10 L, Shell Corena S3 R recommended | The quantity and type of oil for an oil change |
Flow - the figure that counts
Power indicates the size of the motor; flow indicates how much air you will actually have for your tools. This is the figure to compare with your tools' consumption.
Two points to watch:
- Flow depends on pressure. On the S 110, it goes from 1.7 m³/min at 8 bar to 1.1 m³/min at 13 bar. Always compare two machines at the same pressure.
- Intake flow or free air delivery. Intake flow (or displacement, for a piston compressor) measures the air entering the machine. Free air delivery, or FAD, measures the air actually available at the outlet, according to ISO 1217. The second is always lower than the first. When a data sheet does not say, ask which flow is meant. The flow rates on AIRSTAHL data sheets are free air delivery figures, measured to ISO 1217.
Pressure - neither too much nor too little
A higher pressure does not give more air; quite the opposite: on the same machine, flow decreases. Choose the pressure needed by the most demanding tool, plus a small margin for network losses. Our article on calculating your compressor pressure gives the method.
Units and their equivalents
Data sheets do not all speak the same language. Here are the most useful conversions.
| Unit | Equivalent |
|---|---|
| 1 m³/min | 1,000 L/min, or 60 m³/h |
| 1 m³/min | Approx. 35.3 cfm (cubic feet per minute) |
| 1 bar | Approx. 14.5 psi |
| 1 bar | 100 kPa |
The flow and pressure converter does these calculations for you.
Noise level - mind the scale
Decibels follow a logarithmic scale: 3 dB(A) more means double the sound energy, and around ten decibels more is perceived as roughly twice as loud. A difference of a few decibels between two data sheets is therefore not negligible. Also check the distance at which the measurement was taken: two values can only be compared at the same distance. For a workshop where people work next to the machine, read our page on the quiet workshop compressor.
Comparing two data sheets - an example at 11 kW
Here are three of our 11 kW machines. Same power, three ways of working.
| E 110 | S 110 | K 110 | |
|---|---|---|---|
| Technology | Piston, 3 cylinders, belt | Screw, permanent magnet motor | 4-in-1 screw, permanent magnet motor |
| Pressure | 8 bar | 8, 10 or 13 bar | 8, 10 or 13 bar |
| Flow | 1.6 m³/min | 1.7 m³/min at 8 bar | 1.7 m³/min at 8 bar |
| Air receiver | 320 L | No air receiver | 340 L |
| Dryer and filtration | No | No | Built in |
| Dimensions (L × W × H) | 1700 × 640 × 1200 mm | 1050 × 700 × 1000 mm | 1800 × 730 × 1530 mm |
| Weight | 430 kg | 210 kg | 400 kg |
With similar flow, the choice comes down to the work pattern (continuous or intermittent), the air quality expected and the existing installation. The articles on the difference between piston and screw compressors and 4-in-1 or standalone compressor help you decide, and the comparison tool puts the data sheets of your choice side by side.