It’s easy to find the tonnage once you get the hang of it. Hunt for a number that is divisible by 6 or 12 somewhere in the center of the model number on the data plate at the side of condenser (outdoor unit), like 12,18, 24, 30, 36, 42, 48, or 60. 

    A ton of air conditioning equals 12,000 BTU so, for example a “24” in the middle of the model number indicates that it is a 2-ton system, a “30” means 2-1/2 tons, and the “42” in the middle of the model number at the top of the page means the system is 3-1/2 tons.

Here’s a few more examples:
Trane - 4TWR3030A1000AA - 2-1/2 tons
Carrier - 38BYC030360 - 3 tons
York - YCE48B21SA - 4 tons
Goodman  - CPRT36-1 - 3 tons
Trane -  TTR060C100A2 - 5 tons
Goodman -  GSH130241AC - 2 ton

    Your probably noticed that the last model number had two numbers, “30” and “24,” that are both divisible by 6. Several of the others are the same way. Generally, the second number is the right one. Also, the number of tons of cooling capacity indicated is “nominal,” meaning that the actual BTU’s are approximately the number indicated, but may slightly more or less.  

   If you are unsure whether you have found the right two numbers, you can double-check it by looking for the “RLA” rating on the data plate. RLA is an acronym for Rated Load Amperage, and is what the maximum amperage should be when the condenser is up and running. If you divide the RLA by 6 for older units and 5 or 6 for newer units, you should get a number that approximates (not exactly) the tonnage of the system. Make sure you use RLA and not LRA, Locked Rotor Amperage, which is the surge of amps necessary to overcome inertia and start the system. It averages around five times the RLA.

To get specific instructions and an example for your brand, click on one of the links below:

Affinity    Aire-Flo    Airquest    Amana
American Standard    Ameristar    Arcoaire 
Bard    Bryant   CAC/BDP    Carrier
Comfortmaker    Cumberland    Daikin    Ducane
EcoTemp    FHP (Florida Heat Pump)    GE 
Goodman    Grandaire    Guardian    Heil 
International Comfort    Inter-City Products 
Janitrol    Lennox    Luxaire    Maytag 
Miller    Mitsubishi    Nordyne    Nortek 
Panasonic    Payne    Rheem    Ruud
Stylecrest Revolv    Sears Kenmore
Tempstar    Thermal Zone    Trane 
Unitary Products    WeatherKing    Xenon    York

    To determine other key specs of your HVAC system, see one of these other blog posts: 

• How can I find out the SEER of my air conditioner?

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump?  

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 

  To learn more about heating and air conditioning systems, see these other blog posts: 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.