Heating & Air Conditioning Expert with 25 years of experience

Mon-Fri: 08:00 am-5:00 pm

24h Emergency Service

Call Today 888-628-0691

We're Standing By

Why Is Air Conditioner Capacity Usually Measured In Tons?

Why Is Air Conditioner Capacity Usually Measured In Tons

First-time AC-buyers often get perplexed when their vendor offers them a two or four ton AC. It seems very illogical to them why they should install 8000 pounds of load on the wall. If you are on your way to buy your first AC, don’t get baffled by the reference of the tonnage; it has nothing to do with the unit’s weight. The number of tons simply refers to the amount of heat a particular unit can remove from a house within an hour. But how did tonnage become popular as a way of measuring the capacity of an AC unit?  To know that, we must take a flashback in time.

Before the advent of the artificial cooling system, people used blocks of ice to cool their rooms. The ice was harvested in frozen lakes during the winter season, and then stored until it was summer. Before Willis Carrier invented AC, this was the most popular method. According to records, four million tons of ice was harvested in Hudson River in 1890. The amount of energy required to melt a ton of ice in an entire day was 12,000 BTU.

How Do You Equate a Measurement of ‘Ton’ With Air Conditioning Capacity?

According to the laws of Physics, when the ice goes below the freezing point, it starts absorbing heat. Along with it the temperature increases as well. Finally, when the ice reaches its melting point at 32 degrees Fahrenheit, it still absorbs heat, but there is no temperature difference in the ice. On the contrary, it starts melting. The amount of heat needed to melt ice is called the latent heat of fusion. The optimum energy to melt a pound of ice is 143 BTU.

When you have got a pound of ice at 32 degrees Fahrenheit, you need to put in 143 BTU to melt it completely. When there’s a ton of ice to melt, it takes (143 BTU/lbs)*(2000 lbs) of heat to melt it down completely. The figure is 286,000 BTU, and the magnanimity can be guessed by people. How much time will it require to melt the entire ice depends on how quickly the heat can be pumped in. To use a standard period as the reference, 24hours was taken into consideration. If the ice melts uniformly in a span of an hour, the capacity of one ton of AC is near about 12,000 BTU/hour.

Drawing a Direct Reference of an AC’s Capacity

To avoid such a lengthy calculation, the American Society of Mechanical Engineers, suggested a standard reference of refrigeration for a proposed unit of AC. As people started getting used to it, professional organizations regulated the measurement and made ‘ton’ the standard figure of measurement.

Now that you have got an idea, what tons have to do with air-conditioning, do not feel at-loss when shopping for a new AC system for your home. To know more technicalities about the standard measurement of ‘tonnage,’ do contact us here. We will have our expert technicians explain it to you in details.

Archives