Calculating Cooling Loads
Calculating chiller and cooling tower refrigeration loads  in tons.
Cooling towers tons pairs the watercooled chiller tons and the watercooled condenser tons.
Chiller Refrigeration Tons
The process of cooling is called refrigeration. For commercial and industrial refrigeration systems most of the world uses the kilowatt (kW) as the basic unit of refrigeration. Some commercial and industrial refrigeration systems are rated in Tons of Refrigeration (TR, tons).
A waterchiller refrigeration ton is defined as:
1 Refrigeration Ton (RT) = 1 TONS _{ cond } = 12000 Btu /h = 200 Btu /min = 3025.9 k Calories /h = 12661 kJ/h = 3.517 kW
1 kW = 0.2843 Refrigeration Ton (RT)
A ton is the amount of heat removed by an air conditioning system that would melt 1 ton (2000 lbs.) of ice in 24 hours. The heat required to melt 1 lb of ice at 32 ^{ o } F to water is 144 Btu.
1 Ton Refrigeration = (2000 lb) (144 Btu/lb) / (24 hr)
= 12000 Btu/hr
Converting between Btu/h and Tons of Refrigeration
Btu/h  Refrigeration Ton  kW 

6000  1/2  1.76 
12000  1  3.52 
18000  1 1/2  5.28 
24000  2  7.03 
30000  2 1/2  8.79 
36000  3  10.6 
42000  3 1/2  12.3 
48000  4  14.1 
54000  4 1/2  15.8 
60000  5  17.6 
Cooling Tower Tons
A cooling tower ton is defined as:
1 cooling tower ton = 1 TONS _{ evap } = 1 TONS _{ cond } x 1.25 = 15000 Btu /h = 3782 k Calories /h = 15826 kJ/h = 4.396 kW
The equivalent ton on the cooling tower side actually rejects about 15000 Btu/h due to the heatequivalent of the energy needed to drive the chiller's compressor. This equivalent ton is defined as the heat rejection in cooling 3 U.S. gallons/minute (1500 pound/hour) of water 10°F , which amounts to 15000 Btu/hour , or a chiller coefficientofperformance ( COP ) of 4.0  a COP equivalent to an energy efficiency ratio ( EER ) of 13.65 .
Heat Load and Water Flow
A water systems heat load in Btu/h can be simplified to:
h = c _{ p } ρ q dt
= (1 Btu/lb _{ m } ^{ o } F) ( 8.33 lb _{ m } /US gal) q (60 min/h) dt
= 500 q dt (1)
where
h = heat load (Btu/h)
c _{ p } = specific heat, 1 (Btu/lb _{ m } ^{ o } F) for water
ρ = 8.33 (lb _{ m } /US gal) for water
q = water volume flow rate (US gal/min)
dt = temperature difference ( ^{ o } F)
Example  Water Chiller Cooling
Water flows with 1 gal/min and 10 ^{ o } F temperature difference. The ton of cooling load can be calculated as:
h = 500 (1 US gal/min) (10 ^{ o } F)
= 5000 Btu/h
= (5000 Btu/h) / (12000 Btu/ton)
= 0.42 ton
Typical Cooling Loads
Type of Room  Cooling Load (ft ^{ 2 } /ton) 

Arenas  150  200 
Classroom  200  250 
Clean room  100  300 
Conference room  100  200 
Data room  80  100 
Meeting room  200  250 
Office  300  350 
Residence  600  700 
Related Topics

Air Conditioning
Air Conditioning systems  heating, cooling and dehumidification of indoor air for thermal comfort.
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