## How many tons is my Nortek heat pump or air conditioner?

Sunday, May 5, 2019

You can determine the “nominal” size of your HVAC system by examining the model number on the data plate at the side of the condenser (outdoor unit). Just like the nominal size of lumber or an air conditioning filter, the exact cooling capacity may be a little more or less than the nominal rating, but it’s close.

For Nortek, you should look for two numbers at the end of the model number that 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 36 divided by 12 equals 3, so the data plate below indicates the system is 3 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.

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 Nortek system, see our blog post How can I tell the age of a Nortek heat pump, air conditioner, or furnace from the serial number?  For the age of another brand or manufacturer, go to our blog post How do I determine the age of my air conditioner?

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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.

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