A few years ago, a student of mine told a funny story in a home energy rater class. He was an HVAC contractor and said he was installing a new air conditioner for an elderly woman. As he was explaining things to her, he mentioned that they would be installing a 4 ton unit. "Oh, my," she said. "How are you going to get something so big into my backyard?" The confusion here is completely natural. HVAC and home energy pros find this story funny because when you say an air conditioner is 4 tons, we know it's not weight. It's a number that tells how much heat the air conditioner can remove from the house in an hour. (Let's ignore the issues of nominal vs. actual capacity and AHRI de-rating.) A 4 ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the house. For most people, though, 4 tons means 8000 pounds. (A BTU is a British Thermal Unit, approximately the amount of heat you get from burning one kitchen match all the way down.) Most pros also know how such a common term as 'ton' turned into a bit of HVAC jargon.

Before Willis Carrier invented the modern air conditioner, people used to cool buildings in the summertime with ice harvested from rivers and lakes in the wintertime. how much is a new 4 ton ac unitA Green Homes America article quotes ice production figures from the 19th century Ice and Refrigeration journal, indicating that the 1890 crop from the Hudson River was about 4 million tons.used 15 ton ac unit OK, so people used to cool and refrigerate with ice. large window air conditioning unitsHow does that equate to air conditioning capacity in BTUs per hour, you ask? Well, let's get quantitative and find out. When ice is below freezing and it absorbs heat, the temperature increases. When ice is at its melting point, 32° F, and it absorbs heat, its temperature doesn't change.

If you've had a physics or chemistry class, you may recall that the amount of heat needed to melt ice is called the latent heat of fusion. In Imperial units, that number is 143 BTUs per pound. That's actually a lot of heat to pump into a pound frozen water. Once the ice is melted into liquid water, it takes only 1 BTU per pound to raise the temperature 1 degree. So if you've got a pound of ice at 32° F, you put 143 BTUs into it to melt it completely. Then it takes only 180 more BTUs to raise the temperature of that pound of water from 32° F to 212° F, the boiling point. Anyway, getting back to our main discussion, if you have a ton of ice, it takes (143 BTU/lb) x (2000 lbs) = 286,000 BTUs to melt it completely. You could do that in one hour or 10 hours or a year, depending on how quickly you pump heat into it. Somewhere along the line, though, someone decided to use 1 day—24 hours—as the standard time reference here. If the ice melts uniformly over the 24 hours, it absorbs heat at the rate of 286,000 / 24 hrs = 11,917 BTU/hr.

Rounding that number up makes it a nice, round 12,000 BTU/hr. In air conditioning jargon, then, a ton of AC capacity is equal to 12,000 BTU/hr. If you're wondering how this term got institutionalized, it was probably the usual way. People in the industry start using it, and then the professional organizations make it official. An architecture website has a quote from 1912 that claims the American Society of Mechanical Engineers standardized it. It sounds likely, but their numbers don't work out, so I'm gonna go with Honest Abe on this one and remain skeptical. For the fearless: If you want to read some funny HVAC banter on this topic, check out this thread in the HVAC-Talk forum. And if you figure out what 'heat of zaporization' is, let me know! The Magic of Cold, Part 1 - How Your Air Conditioner Works It's Called an Air Conditioner — Not an Air Cooler! 5 Questions to Ask When Replacing Your Air Conditioner , used under a Creative Commons license. Photo of ice harvest by Robert N. Dennis, in the public domain, from Wikimedia Commons.

Abe Lincoln photo and quote from The Canterbury Tales by Chaucer. See more product details Garrison GSC130241 2 Ton 24000 Btu 208/230V 15 Amp Gx Series 13 Seer R-22 Condensing Unit For dependable, year-after-year cooling performance, install this ETL-listed air conditioner. It provides durability, value, and trouble-free performance. ^^Unit Features Energy-Efficient Compressor Louvered Sound Control Top for Quiet Operation Factory-Installed Liquid Line Filter Dryer Copper Tube/Aluminum Fin Coil Brass Liquid and Suction Service Valves Sweat Connections Included Contactor with Lug Connections Ground Lug Connection^^Cabinet Features Louvered Sound Control Top Steel Louver Coil Guard Heavy-Gauge Galvanized Steel Cabinet Architectural Gray Powder Paint Finish500-Hour Salt Spray Approval^^Important Informational units are shipped containing a charge of nitrogen and helium. These inert gases must be evacuated before you can charge the system with R-22. ^^Warranty This R-22 air conditioner comes with a limited five-year warranty.

It covers all functional parts should a problem arise. This is manufactured in United States. 34.8 x 26 x 26 inches Lighting & Fans, Ceiling Fans & Ventilation, ceiling-fan-wall-controls 5.0 out of 5 stars #487,992 in Home Improvements (See top 100) #1,896 in Home Improvement > Appliances > Air Conditioners & Accessories > Air Conditioners Currently, item can be shipped only within the U.S. and to APO/FPO addresses. For APO/FPO shipments, please check with the manufacturer regarding warranty and support issues. This item is not eligible for international shipping. Would you like to update product info or give feedback on images? 25 star100%See all 2 customer reviewsTop Customer ReviewsPerfect Replacement Unit! What Other Items Do Customers Buy After Viewing This Item? R-22 Refrigerant 10 Lb Cylinder Honeywell RTH9580WF1005/W1 Wi-Fi Smart Touchscreen Thermostat, Silver, Works with Alexa (no hub required) Packard TRCFD355 35+5 MFD 440/370V ROUND Capacitor