MINIMUM AIR VELOCITY
For a longer coil life and satisfactory heater performance, each heater is labeled with the minimum air velocity. Air velocity should not fall below these figures. If for any reason these figures cannot be reached, contact the factory. To find your minimum FPM ratings for a heater follow the steps below:
1. Take outside duct size (HxW) and multiply by 1000.
2. Divide that figure by 144.
3. Take Watts and divide by figure in step 2. This would give you watts per square feet.
4. GO to the chart and find your FPM per inlet air.