Air Conditioner Capacity Measurement

Capacity of an Air Conditioner always measure on ton. You can hear 1ton or 3 ton AC. We know that ton is a measuring unit of mass. So, this question must be arise on your mind, why the capacity of an Air Conditioner measuring in ton??!! Now, before getting the answer of your question, I want to review some old school topics.

There are two measuring system using world wide – Metric System and Imperial System. I am not going to describe these systems.

Now,

1 ton = 2204.62 lb = 1000 Kg

1 short tone = 2000 lb = 907.185 KG

For Temperature,

0˚C = 32˚F = 273 K

100˚C = 212˚F = 373K

Now come to the Ice. If temperature increases, below freezing ice absorbs the heat and increasing its temperature. When temperature increase to its melting point (Means 32˚F or 0˚C), the temperature of ice doesn’t change, it changes its state and start melting. It means, in a constant temperature (32˚F or 0˚C) ice only changes its phase. It is called the latent heat of fusion and its amount is 143 BTU/lb in Imperial system and 332.6 KJ/kg in Metric.

After changing its phase, when ice melting to water, it takes only 1 BTU/lb to rise the temperature 1˚F. So, at 32˚F we need 143 BTU for completely melt one pound of ice, and then, rising to its boiling point 212˚F or 100˚C we need 180 BTU (212˚F – 32˚F = 180˚F).

Here now we do a simple calculation. For, 1 ton (US ton or short ton) of ice, 143 BTU/lb × 2000 lb = 286000 BTUs needs to melt it completely. It will take 5 hours or 10 or 24 hours. It depends on how quickly we force heat in to it. For a standard time reference, we take it 24 hours. So, 1 ton (US ton or short ton) of ice melts in 24 hours and absorbs heat 286000 BTU. The rate of absorbs heat is 286000 BTU / 24 hours = 11917 BTU/hr. So it is approximately 12000 BTU/hr. British Thermal Unit (BTU) is the traditional unit of work. 1 BTU is the amount of work required to raise the temperature of 1 lb (Pound) of water by 1˚F.

Finally,

1 watt ≈ 3.41214 BTU/hr and

1 ton (US ton or short ton) = 12000 BTU/hr. So,

1 ton (US ton or short ton) = (12000 / 3.41214) Watt

=> 1 ton = 3516.8545 Watt = 3.5168 KW = 4.714 Hp                   

Basically, an Air Conditioner removes hate from an area. So, the capacity of an Air Conditioner stands on how much heat it can removes from a closed area. Whereas, an Air Conditioner designed for removes heat amount of 12000 BTU per hour from a selected closed area, therefore, the capacity of an Air Conditioner measure in ton (US ton or short ton). This also applicable for refrigerator or fridge.