Air Handling Units - Page 3

The following fan curves were developed from test data taken in accordance with AMCA standards for forward curved fans. Belt losses are not included. For TSP greater than listed on the individual fan curves shown, contact factory for backward incline fan selections.

FAN SELECTION EXAMPLE

PROBLEM:

Select SB ventilating unit and motor horsepower to deliver 6,000 SCFM at 1.50" w.c. total static pressure. Desired motor type is single speed, 1800 RPM, drip-proof.

SOLUTION:

1. Check fan performance curves for smallest SB model which will handle the specified air flow and total static pressure. This proves to be the SB-115.
2. Locate 6,000 SCFM on the horizontal axis of the SB-115 fan performance curve and move vertically to the point of intersection with the 1.50" w.c. total static pressure line. This defines the operating point; fan speed wil be 920 RPM and the motor will draw 3.5 HP. The next larger size motor, 5 HP, is required.
3. From the Reference Table on this page, we find that the 5 HP, 1800 RPM, dripproof motor has a 184T frame size. This size is smaller than the maximum motor frame size of 213T shown on SB-115 fan performance curve, so selection is acceptable.
4. From the SB-115 performance curve, the fan outlet velocity is shown to equal SCFM/2.28. At the operating point of the selected unit, the outlet velocity is 6,000/2.28 or 2,632 FPM.

MOTOR FRAME SIZE REFERENCE TABLE

NOTES:

1)  All motors are three phase.

2) Motors less than 1.5 HP have frame sizes that will fit within any SB model ventilating unit cabinet.

3) SB-240 maximum frame size, 405T. For larger frame sizes consult factory.

STANDARD ENERGY EFFICIENT MOTOR REFERENCE TABLE