The most common sizing mistake is adding up the nameplate air consumption of every tool and buying a compressor for that total. Real demand is lower because not everything runs at once, but it must be measured and calculated, not guessed.
Step-by-step method
- List every air consumer and its CFM at working pressure
- Estimate the utilisation of each, usually 0.2–1.0
- Group consumers by the shift in which they run
- Find the maximum simultaneous demand in the busiest period
Add the right margin
Add 10–20% for leaks and future growth, then add the pressure drop of the distribution network to the required pressure. This gives both the flow and pressure the compressor must deliver at the point of use.
Verify with measurement
Where an existing system is being upgraded, measure the real load with a flow meter over a representative week. The measured profile removes the guesswork and often shows the demand is lower, and more variable, than the calculation suggests.