The Reason Air Conditioner Capacity Is Measured in Tons

Air conditioner capacity is one of the most important factors to understand when you’re choosing a new cooling system for your Texas home. You probably already realize your air conditioning unit doesn’t weigh several tons, so the use of this measurement may seem a little illogical. In fact, the use of tons to measure air conditioner capacity doesn’t originate so much from a deliberate decision as from historical customs.

Before electric air conditioners existed, people used large blocks of ice to cool their homes and businesses. The ice absorbed heat and slowly melted as it warmed up. The use of tons to measure cooling capacity comes from this time. A ton refers to the amount of heat it takes to completely melt a ton of ice. Melting this amount of ice requires 286,000 Btu (British thermal units).

How fast the ice melts depends on how much heat it receives over time. For consistency, though, HVAC technicians began using 24 hours as their standard time period for air conditioners. Under standardized conditions, melting a ton of ice in 24 hours requires 11,917 Btu/hr.

Air conditioners work something like blocks of ice in that they don’t produce cool air, but rather remove heat from the building. The capacity of an air conditioner refers to the amount of heat it can remove. Rounding up 11,917 Btu/hr gives you 12,000 Btu/hr, which is one ton of air conditioner capacity.

To determine how much heat must be removed to cool your home – your home’s cooling load – your HVAC contractor will follow the guidelines set forth in the ACCA’s (Air Conditioner Contractors of America) Manual J.

In addition, your contractor should follow Manual S. This manual contains manufacturer performance tables, which tell your contractor about the true capacities of different A/C systems in the conditions relevant to your home.

The energy efficiency and performance of your A/C system depends on correct sizing, equipment selection and installation. If you want your new air conditioner installed right, please contact us at Davis Air Conditioning & Heating, Inc.. anywhere in the Houston, Angleton, Ft. Bend, Galveston, Sugar Lane or Brazoria areas.