3 Calculate the motor speed for each part-load bin. A warehouse freezer (-20 F)
ID: 1843795 • Letter: 3
Question
3 Calculate the motor speed for each part-load bin.
A warehouse freezer (-20 F) is served by four (4 evaporator coils. The full refrigeration load in the freezer is 50 tons. Each coil has four (4) fans, each driven by a 5-horsepower motor running at full speed. The customer is considering retrofitting the fan motors with variable frequency drives (VFDs), with a total project cost of $72,000. The refrigeration compressors serve other loads and operate at 1.8 BHP/ton. The customer's marginal cost of electricity is S0.085 per kWh. The load profile in the freezer is as follows: Percent of hours in year Percent of full refrigeration load 2% 100% 10% 95% 12% 90% 150% 885% 20% 80% 150% 75% 70% 13% 10% 65% 13% 60% The facility operates continuously, except for a one-week shutdown each year. Each coil is defrosted four (4) times per day for 30 minutes per defrost cycle The VFD efficiency is 96% across the range of expected operation. The fan motors are three-phase NEMA premium efficient motors with an efficiency of 90%. At full speed in this application the motors operate at a load factor of 85% 1. Calculate the annual energy savings for this project (kilowatt-hours and dollars) 2. The customer requires a 2.5year simple payback to proceed with a project. How much financial assistance will be needed to meet the customer's financial requirement?Explanation / Answer
The answer of following question is as follows.
The motor speed for each part load bin is 810 rpe.
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