How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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How many tons is my Carrier air conditioner or heat pump?
Wednesday, March 13, 2019
You can determine the size in tons of your Carrier HVAC system by examining the model number on the data sticker at the side of the a/c condenser (outdoor unit). Look for the 7th and 8th digits, or maybe 8th and 9th digits, of the model number. It will be a number divisible by 6 or 12, and represents 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 the one below is a 2 ton unit.
. If the condenser is older and has had years of direct sun exposure, the numbers may be faded away, like in the photo below. But the printing is slightly raised and, if you hold a flashlight close to the surface of the data plate and parallel to, often it is possible tease out the numbers.
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 age of a Carrier system, see our blog post How can I tell the age of a Carrier air conditioner from the serial number?
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To learn more about heating and air conditioning systems, see these other blog posts:
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