How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
How many tons is my Grandaire air conditioner or heat pump?
Tuesday, April 9, 2019
You can determine the size in tons of your Grandaire HVAC system by examining the model number on the data plate at the side of the a/c condenser (outdoor unit). Look for two numbers in a cluster in the middle of the model number. They are divisible by 6 or 12, and represent the nominal BTU of the system in thousands. A ton of air conditioning equals 12,000 BTU, and 48 divided by 12 equals 4, so the data plate below indicates the system is 4 tons.
Here’s a rundown of the range you will encounter: 18 = 1.5 tons, 24 = 2 tons, 30 - 2.5 tons, 36 = 3 tons, 42 = 3.5 tons, 48 = 4 tons, and 60 = 5 tons. And this is another one for a 3 ton system.
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 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 determine the date of manufacture of a Grandaire system, see our blog post How do I tell the age of a Grandaire air conditioner or furnace from the serial number? To find out the age of another brand of air conditioner or heat pump, go to How do I determine the age of my air conditioner?
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
To learn more about heating and air conditioning systems, see these other blog posts:
• How can I find out the SEER of my air conditioner?
• My air conditioner won't turn on. What's wrong?
• How can I find out the size of my air conditioner?
• How can I find out the age of my air conditioner or furnace?
• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump?
• 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.
of Blog Posts
Top 5 results given instantly.
Click on magnifying glass
for all search results.
Buying a home in North/Central Florida? Check our price for a team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.