Converting kW/ton to COP or EER
How to convert between kW/ton, COP and EER
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The chiller efficiency depends on the energy consumed. Absorption chillers are rated in fuel consumption per ton cooling. Electric motor driven chillers are rated in kilowatts per ton cooling.
- KW/ton = 12 / EER
- KW/ton = 12 / (COP x 3.412)
- COP = EER / 3.412
- COP = 12 / (KW/ton) / 3.412
- EER = 12 / KW/ton
- EER = COP x 3.412
If a chillers efficiency is rated at 1 KW/ton,
- COP = 3.5
- EER = 12
Cooling Load in - kW/ton
The term kW/ton is commonly used for larger commercial and industrial air-conditioning, heat pump and refrigeration systems.
The term is defined as the ratio of energy consumption in kW to the rate of heat removal in tons at the rated condition. The lower the kW/ton the more efficient the system.
kW/ton = Pc / Er (1)
where
Pc = energy consumption (kW)
Er = heat removed (ton)
Coefficient of Performance - COP
The Coefficient of Performance - COP - is the basic parameter used to report efficiency of refrigerant based systems.
The Coefficient of Performance - COP - is the ratio between useful energy acquired and energy applied and can be expressed as
COP = Eu / Ea (2)
where
COP = coefficient of performance
Eu = useful energy acquired (btu in imperial units)
Ea = energy applied (btu in imperial units)
COP can be used to define both cooling efficiencies or heating efficiencies as for a heat pumps.
- Cooling - COP is defined as the ratio of of heat removal to energy input to the compressor
- Heating - COP is defined as the ratio of heat delivered to energy input to the compressor
COP can be used to define the efficiency at single standard or non-standard rated conditions, or as a weighted average of seasonal conditions. The term may or may not include the energy consumption of auxiliary systems such as indoor or outdoor fans, chilled water pumps, or cooling tower systems.
- higher COP - more efficient system
COP can be treated as an efficiency where COP of 2.00 = 200% efficiency. For unitary heat pumps, ratings at two standard outdoor temperatures of 47oF and 17oF (8.3oC and -8.3oC) are typically used.
Energy Efficiency Ratio - EER
The Energy Efficiency Ratio - EER - is a term generally used to define cooling efficiencies of unitary air-conditioning and heat pump systems.
The efficiency is determined at a single rated condition specified by an appropriate equipment standard and is defined as the ratio of net cooling capacity - or heat removed in Btu/h - to the total input rate of electric power applied - in Watts. The units of EER are Btu/Wh.
EER = Ec / Pa (3)
where
EER = energy efficient ratio (Btu/Wh)
Ec = net cooling capacity (Btu/h)
Pa = applied electrical power (Watts)
This efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans.
- higher EER - more efficient system
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Related Topics
- Air Conditioning - Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort
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Related Documents
- Air Conditioner Efficiency - Air conditioner efficiency express the ratio between heat removed to watt of power used - EER and SEER
- Calculating Cooling Loads - Calculating chiller and cooling tower refrigeration in tons
- Cooling Tower Efficiency - The maximum cooling tower efficiency is limited by the wet-bulb temperature of the cooling air
- Heat Pumps Performance and Efficiency Ratings - Rating performance and efficiency of heat pumps
