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Fan and Pump Affinity Laws

Drop a fan to 80% speed and you use roughly half the power. This is the arithmetic behind every VFD energy conversation.

Free tool · BAS Field Fundamentals

Works offline. Every calculation runs on your device, no signal needed. Install the BAS Field Reference app to keep it on your phone.

How to use it

  1. Enter the current operating point — speed, flow, head and power as you know them.
  2. Enter the new speed you are considering, in Hz or percent.
  3. The results are theoretical. Real systems fall short because motor and drive efficiency change with speed, and static head does not scale.
  4. Use it for the order of magnitude, not for a guarantee.

Background reading: The 8 Parameters You Need From Any VFD →

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More where this came from

This calculator comes out of BAS Field Fundamentals — the meter tests, the maths and the failure modes for every sensor, drive and control loop in the building, plus 20 field cases and a browser simulator to practice on.

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