GATE Architecture

GATE 2013

Star Rating of an Air Conditioner is determined by its

(A) Power Consumption
(B) Energy Efficiency Ratio
(C) Cooling Capacity
(D) Power of Compressor

Answer: (B) Energy Efficiency Ratio

Energy Efficiency Ratio= (Cooling capacity)/(Power consumption)

For air conditioners, the measure of energy efficiency is the Energy Efficiency Ratio (EER) for cooling and the Coefficient of Performance (COP) for heating. The EER and COP are defined as the capacity output divided by the power input.
Cooling capacity is the amount of heat energy removed by the Air conditioner from a space for a given time. It is generally measured in British Thermal Unit (BTU) per hour (BTU/Hr). In SI units it is measured by KJ / Sec= KW.
Both cooling capacity and power consumption is measured in watt.
A refrigeration ton is approximately equivalent to 12,000 BTU/h or 3,517 W.
1 Btu= 1055 Joules
EER (W/W) of 3.40 gives a 5 – Star Rating which means for every watt of power consumed 3.40 W (3.4 Joules/sec) of heat energy is removed by the air conditioner.
Bureau of Energy Efficiency under Ministry of Power, Govt. of India was formed in the year 2002, under the provision of Energy Conservation Act, 2001. All electrical appliances should have star rating that determines its Energy Efficiency.
The Energy Conservation Building Code (ECBC) was launched in 2007, which promotes Energy Efficiency in Building Sector.

Star Rating of Geyser is determined by its ‘Standing Loss’ (kWh/ 24 hr)

Practice Question.
Q: A two ton AC has EER of 3.5. Calculate its power consumption.
Soln.
EER= Cooling capacity/ Power consumption
Given EER= 3.5
Cooling capacity = 2 ton
= 2x3517= 7034 Watt (since 1 ton ≈3517 W)

3.5= 7034/(Power Consumption@)
Power consumption=7034/3.5 = 2009.7 W (say 2 KW)

(Note: In the above question 2 KW of power consumption transfers 7034 W of power from inside to outside)

source: GATE Arch/Planning by B K Das