Word of the Day Nearby words for air-condition 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. A 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. OK, so people used to cool and refrigerate with ice. How 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.should an ac window unit be level 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. auto upholstery repair tempe azYou could do that in one hour or 10 hours or a year, depending on how quickly you pump heat into it. outside ac unit replacementSomewhere 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! 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. heating & cooling distribution,Written Upvoted by Loring Chien, Written You will find the below link very informative in regards to AC power and efficiency information (India-centric)Air conditioner selection: understand Tonnage, EER, COP and Star RatingIn simple termsI ton AC will remove heat equivalent to melt 1 ton of ice in 24 hoursThis is equal to 12000 BTU (British Thermal Unit) per hourThis is the cooling capacity rating found in most International (non Indian) AC specification sheets and websitesThis is equal to 3517 Watts per hourThis is the cooling capacity rating found in most Indian AC specification sheets and websitesBe aware... The mechanical systems that provide thermal comfort and air quality in an indoor space are often grouped together because they are generally interconnected.

HVAC systems includes central air conditioners, heat pumps, furnaces, boilers, rooftop units, chillers, and packaged systems. Right-size Heating and Cooling Equipment Last Updated: Apr 30, 2015 3:50pm Was the information on this page helpful? Topic Categories and Standalone Pages Explore more content from North Carolina Cooperative Extension ▲Air Wisconsin Airlines Corporation air your dirty laundry in public Air, Land and Sea air, law of the Air, Noise, & Radiation Health Research Division Air, Noise, and Radiation Programs Air, Pesticides and Toxics Management Division Air, Rail, Water, and Pipeline Air, Resource Conservation and Recovery Act and Toxics Division Air, Space and Cyberspace Constructive Environment Air, Toxics & Radiation Monitoring Division Air, Trees, Water, Animals Air, Water, and Aquatic Environments Science Program Air-Actuated Hydraulic Swaging UnitA forced-air HVAC system distributes conditioned air through a plenum.

A household forced-air heating, ventilation and air conditioning system depends on a system of ducts to provide a controlled path for distributing heated or cooled air throughout the home. Typically, HVAC duct systems are made of sheet metal, but other rigid heatproof materials such as fiberglass or insulated plastic may be used. Regardless of construction material, the heart of an HVAC duct system is the plenum. Supply Plenum A plenum is an air-distribution box attached directly to the supply outlet of the HVAC equipment that heats or cools the air to make the house comfortable. The ductwork that distributes the heated or cooled air to individual rooms of the house connects to the plenum. The HVAC equipment has a blower that forces heated or cooled air into the supply plenum and from the plenum into the rooms through the supply duct system. Air-cleaning filters may be located in the supply plenum. Return Plenum Forced-air systems also have return ducts that connect to the HVAC equipment through an air-collection box known as a return plenum.