What is the new CFM the AHU can deliver to the room? What is the new HP of the fan motor? What is the new static pressure that the fan can now overcome? How long (years) will it take to recover the cost of the VFD if electricity is $0.22/kWh?
A constant volume (CV) air handling unit delivers 10,000 cfm of air to a The supply fan inside the unit operates at 1,750 RPM and is designed to overcome 2.5 inches of static pressure. The fan motor is 20 HP and the air handling unit operates for exactly half of the year.
A variable frequency drive (VFD) is installed on the supply fan at a cost of
$12,000, now making this a VAV unit. Using the VFD, the fan speed is reduced by 20%.
Answer the following questions:
What is the new CFM the AHU can deliver to the room? What is the new HP of the fan motor?
What is the new static pressure that the fan can now overcome?
How long (years) will it take to recover the cost of the VFD if electricity is
$0.22/kWh?
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