Your Air Conditioner: Know Why Its Capacity Is Expressed in Tons?

While it’s true that an air conditioner with a significantly larger capacity will tend to weigh more than one with a smaller capacity, the reason air conditioner capacity is measured in tons actually has nothing to do with the weigh of the air conditioners themselves. Measuring air conditioner capacity in tons actually pre-dates air conditioning; it arose during the eras when buildings were cooled with ice that had been harvested from frozen lakes and rivers.

The heat removal capacity of a ton of ice is easily determined because it takes a specific amount of heat to change a given amount of ice into water. The only complication is that you also want to know how fast the heat can be removed. Back when ice was in use, it was more useful to look at heat removal capacity on a daily basis, but with air conditioner’s ability to be turned on only when needed, it’s more useful to know the hourly heat capacity removal. This means you have to divide the heat removal capacity of a ton of ice by 24 to get the hourly capacity of an air conditioner. This results in one ton of capacity being equivalent to the removal of 12,000 British thermal units (BTU) of heat per hour.

Determining the heat removal capacity of an air conditioner is not nearly as simple as it is for ice. A/Cs’ heat removal capacity depends on multiple factors, including the indoor temperature, humidity and the outdoor temperature. The Air Conditioning, Heating and Refrigeration Institute (AHRI) offers standardized capacity ratings that are more useful than the manufacture’s nominal rating, but they still might not be accurate for your home. The only way to really know how much capacity an air conditioner will have when installed in your home is to have a contractor perform calculations using Manuals J and S from the Air Conditioning Contractors of America.

An improper installation can also affect air conditioner capacity, so make sure installations are done by a quality contractor. If you need help in Martin, Palm Beach or Indian River counties, please contact us at NisAir Air Conditioning & Heating.