As you change altitude, it is important to make adjustments to your air flow design. This is because increasing altitude results in a reduction in air density and an increase in cubic feet per pound. The reduction in air density means that less air is crossing the coil. As you go higher, you will need to move more cubic feet per minute (cfm) in order to achieve the same mass flow as at sea level. For instance, at sea level, 1 lb of air occupies 13 cubic feet, whereas at 5000 ft, it takes approximately 16 cubic feet. Consequently, at sea level, you would need to move 250 cfm per ton and have 8 outlets per ton. However, at 5000 ft, you would need to move 300 cfm per ton and have 10 outlets per ton.
If you have any concerns about high altitude installations, please refer to our technote #103 or contact Unico technical support. It's worth noting that the capabilities of the blower may be exceeded due to the change in air density.