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REFRIGERATION HVAC MECHANIC RED SEAL LICENSE EXAM REVIEWER - cooler/reefer tonnage capacity
PROBLEM:
An 8 x 20 ft sea container reefer walkin cooler has an hourly load of 22,500 Btu/hr and operates 24 hours a day. The defrost system runs for 15 minutes every hour. Calculate the tonnage capacity in Tons of Refrigeration and in Kilowatts.
Given
22,500 Btu/hr hourly load
24 hours operation
15 minutes defrost per hour
Unknown
Reefer capacity in tons and KW
SOLUTION:
Total defrost time
= 15 minutes x 24
= 360 minutes
= 6 hours
Total Run-Time
= 24 - 6
= 18 hours
Q = hourly load
x 24/run time
Walk in Cooler Condensing Unit capacity
= ( Hourly Load x 24 hr ) / 18 hr Run-Time
= ( 22,500 x 24 ) / 18
= 30,000 Btu/hr
Tonnage capacity = 30,000/12,000 = 2.5 tons
Capacity in Kilowatts = 2.5 x 3.5 = 8.8 KW
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