How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
How do I tell the size in tons of a RunTru heat pump or air conditioner from the serial number?
Sunday, October 31, 2021
For size in tons of RunTru unit, you should look for two numbers in the middle of the model number on the condenser data plate 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, so the RunTru model number A4HP4030A1000A is a 2-1/2 ton unit because 30 divided by 12 equals 2.5. Another example is 4WCA4060A1000A, which is 5 tons. And the one shown below is 3-1/2 tons.
Occasionally there is a number that doesn’t quite fit the format, and A4HP4023A1000A is an example from RunTru. It is a 2 ton unit.
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.
• • • • • • • • • • • • • • • • • • • • •
Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
• • • • • • • • • • • • • • • • • • • • • •
To learn more about heating and air conditioning systems, see these other blog posts:
of Blog Posts
Top 5 results given instantly.
Click on magnifying glass
for all search results.
Buying a home in North/Central Florida? 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.