Wonder Why Air Conditioner Capacity Is Measured in Tons? Here’s the Story

Before modern air conditioning, there was an ice industry. Ice harvested from frozen river and lakes became the main component of early refrigeration for food and air conditioning. Modern measurements of air conditioner capacity still use terms related to ice and water. The measurements describe how much heat it takes to melt one ton of ice in 24 hours. To break it down:

  • One BTU equals the heat of one wooden match.
  • It takes 288,000 BTUs to melt a ton of ice in a day.
  • Every hour, it takes 12,000 BTUs to melt the ice.
  • One ton of cooling is equal to 12,00 BTUs per hour.
  • A 3-ton A/C removes 36,000 BTUs of heat per hour from your home.
  • Three tons is the nominal capacity, which may differ from actual capacity.

Although your A/C may have a 3-ton capacity, that doesn’t mean that it will perform accordingly all the time. Air conditioner capacity in new systems is indicated by an Air Conditioning, Heating and Refrigeration Institute rating. Actual capacity is frequently lower than nominal capacity, partly because testing conditions are frequently different from actual operating conditions. An incorrect refrigerant charge, ductwork problems and a dirty coil or air filter can also significantly influence capacity.

The bottom line is this: You may think a 3-ton air conditioner suits your needs, but you may actually need a larger unit. This is a problematic area, however, because an air conditioner that’s oversized can give you many headaches for years to come. The only qualified person to make that assessment is an expert HVAC-system contractor, who will do an accurate load calculation using the industry-standard Manual J and Manual D methods. Only an accurate load calculation can determine the size that your home needs.

Are you shopping for an air conditioner? Contact Beyer Boys. We can see to it that you get the system that’s sized and installed correctly. We serve homeowners throughout San Antonio, and we’re the very proud recipients of the Angie’s List Super Service Award for 2012.

Our goal is to help educate our customers in the greater San Antonio, Texas area about energy and home comfort issues (specific to HVAC systems).

Quick & Easy Estimates

AC Ducts Cleaning - Air Conditioner Unit Systems

Get Service Calls