How to Select the Correct Regenerative Blower

Blower selection starts with the amount of air required at the pressure or vacuum the system actually creates. Add electrical supply, site conditions and operating environment, then select a model whose published curve covers that operating point with appropriate margin. Flow alone is never enough, because delivered flow falls as system pressure rises.

The information you need

• Required airflow in SCFM
• Required operating pressure or vacuum, usually in inches of water gauge
• Pressure or vacuum service
• Voltage, phase and frequency
• Site altitude
• Inlet air temperature
• Operating environment and corrosion exposure
• Duty cycle
• Connection size and piping arrangement
• What the air is doing in the system

For diffused aeration

Start with the diffuser manufacturer’s airflow requirement and the number of diffusers. Then work out the pressure: submergence, diffuser loss, piping and fitting loss, and a fouling margin. As a rough physical relationship, one foot of water depth is approximately 12 inches of water column before other system losses are added. For reference, 27.7 inches of water gauge equals 1 PSIG.

Check the operating point thermally

A model that reaches the duty point on the flow curve can still be running too hot. Per the manufacturer, motor winding temperature, meaning rise plus ambient, should not exceed 140°C for Class F or 120°C for Class B, and blower outlet air temperature should not exceed 140°C. Published curve maximum points assume 40°C inlet and ambient temperature; above that, consult the factory.

Common selection mistakes

• Sizing on free-air flow and ignoring operating pressure
• Ignoring diffuser fouling and future pressure rise
• Using sea-level performance without correcting for elevation
• Selecting standard construction for a corrosive environment
• Oversizing and then controlling by excessive throttling, which drives the blower up its curve and causing it to over heating
• Omitting required filtration or relief protection
• Trying to correct undersized piping by installing a larger blower

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