David B.: Hey, I did mention that issue here! As he was explaining things to her, he mentioned that they would be installing a 4 ton unit. Very Interesting! So in that sense, tons of ice was also a rate. A 3-, 4-, or 5-ton unit doesn’t refer to the weight of the equipment, but instead to the amount of heat the air conditioner can remove from the home in one hour. Yo, Alison. 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. Somewhere along the line, though, someone decided to use 1 day—24 hours—as the standard time reference here. For most people, though, 4 tons means 8000 pounds. Are Tons and BTU’s of Air Conditioning The Same Thing? The do it yourself resource for everyone from Oliver’s expert service technicians. Therefore, the more tonnage an AC unit is rated at, the more air it can cool. Enjoyed the post, Chaucer included. Here's the actual source:    http://bit.ly/Pwiwuo. If you're wondering how this term got institutionalized, it was probably the usual way. grusso: You ask a great question, and it's not because of lack of brain power on your part that this doesn't make sense. For the fearless: If you want to read some funny HVAC banter on this topic, check out this thread in the HVAC-Talk forum. Check out our extended glossary to learn more about other HVAC terms. "How are you going to get something so big into my backyard? A four ton unit can move 48, 000 BTUs and so on. Thanks for that link to an original source from 1920. BTW, the website you linked to with the bit about the ASME had a typo (228,000 vs. 288,000). You could do that in one hour or 10 hours or a year, depending on how quickly you pump heat into it. When ice is below freezing and it absorbs heat, the temperature increases. So if you've got a pound of ice at 32° F, you put 143 BTUs into it to melt it completely. Proudly Serving My air conditioner is not cooling! Tons is a shorthand phrase that refers to the total cooling capacity of the unit in BTU’s. A 4 ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the house. Made me wonder exactly how the cooling worked, so I started looking and found that new buildings are also implementing ice cooling systems ! Should I cover my outdoor air conditioning unit during the winter? Just fill in your home’s square footage, the number of occupants and windows in the form below. I thought not a single person would notice Chaucer in there. A BTU is the amount of energy required to heat or cool one pound of water by one degree Fahrenheit. Rounding that number up makes it a nice, round 12,000 BTU/hr. An architecture website has a quote from 1912 that claims the American Society of Mechanical Engineers standardized it. Check out our. Apply the tonnage to the space. What amount of Btu and Tonnage should your air conditioner have in order to properly cool your home? This form collects your personal information so that we can process and reply to your request. A few years ago, a student of mine told a funny story in a home energy rater class. What Size Air Conditioner Do I Need For My House? Original upstairs system is 18 yrs old, 2.5 ton - 75,000 BTU. See instantly how much money your new air conditioner can save you! People in the industry start using it, and then the professional organizations make it official. Name (required)Phone (required)Email (required)Message (required) I am in Sarasota or Charlotte County, FL.