Duty Cycle Guide
Duty cycle is the percentage of CFM your application demands VS the CFM output of your air compressor.
i.e. Compressor CFM output @ 175psi is 28 CFM and your application’s demand at 175psi is 14 CFM. 14 CFM demand divided by 28 CFM output = 50% Duty cycle.
| Maxium Duty Cycle | Castair Series |
| 100% | Rotary Screw series |
| 85% | Industrial series piston: Super heavy duty, ie: 5hp motor 10hp pump running 445 RPM. |
| 70% | Industrial series piston: Standard duty, ie: 5hp motor with 5hp pump running 767 RPM. |
| 60% | Belt Drive Contractor & Commercial series. |
| 50% | Garage & Direct Drive Contractor series. |
Note: Piston applications with a demand of 50% or more for over 1 hour at a time on a regular basis should be ordered with the dual control option. See page 28 for more details on dual controls. Rotary screw applications should have a minimum of 50% demand or more on a consistent basis or a piston with dual control is recommended.
Facts about horse-powers of electric motors
This is the information you will need to sell Castair units that are many times advertised at much lower horse-power ratings than most of our competitors, this is because we are not stretching the truth. It takes 8.8 amps @115 volts or 4.4 amps @230 volts to equal one horse-power on single phase electricity. Make sure your customers compare amp draw, not advertised horse-power. Always remind them that they are buying cubic feet of air per minute (CFM) not horse-power, and amp draw
Generator Guide
Watts needed to run an electric 1 – phase air compressor;
Motor amps x volts = watts to run x 5 = watts to start air compressor.
ie; 22amps x 230volts = 5060watts x 5 = 25,300watts
Note: It takes 5-times the watts to start than to run.
Typical Electric Wire & Breaker sizes chart
| Copper wire size | Max Amps (Circuit breaker size) |
| No. 18 wire | 7 amps |
| No. 16 wire | 10 amps |
| No. 14 wire | 15 amps |
| No. 12 wire | 20 amps |
| No. 10 wire | 30 amps |
| No. 8 wire | 40 amps |
| No. 6 wire | 50 amps |
| Copper wire size | Max Amps (Circuit breaker size) |
| No. 4 wire | 70 amps |
| No. 3 wire | 80 amps |
| No. 2 wire | 90 amps |
| No. 1 wire | 110 amps |
| No. 1/0 wire | 125 amps |
| No. 2/0 wire | 145 amps |
| No. 3/0 wire | 165 amps |
As a general rule take the motors full load amp (FLA) x 1.25 or (25%) = To determine your breaker & wire size.
Note: For longer runs, larger breakers & wire sizes must be used to overcome the voltage loss caused by the wires’ resistance.
Caution: