A 4 ton air conditioner is one that can remove 48,000 BTUs of heat for every hour from the house. For a great number of people, however, 4 tons means 8000 pounds. (A BTU is a British Thermal Unit, roughly the amount of heat you get from burning one kitchen coordinate right down.)
Most pros additionally know how such a common term as ‘ton’ transformed into a bit of HVAC jargon. Before Willis Carrier designed the advanced air conditioner, people used to cool buildings in the late spring with ice harvested from waterways and lakes in the wintertime. A Green Homes America article statements ice creation figures from the nineteenth century Ice and Refrigeration journal, demonstrating that the 1890 crop from the Hudson River was around 4 million tons.
Air Conditioning Capacity
Alright, so individuals used to cool and refrigerate with ice. How does that compare to air conditioning capacity in BTUs every hour, you inquire? All things considered, how about we get quantitative and discover.
At the point when ice is freezing and it absorbs heat, the temperature increments. At the point when ice is at its melting point, 32° F, and it absorbs heat, its temperature doesn’t change. Rather, it melts. On the off chance that you’ve had a chemistry or physics class, you may recall that the measure of heat required to melt ice is known as the latent heat of fusion. In Imperial units, that number is 143 BTUs for each pound.
That is entirely part of heat to pump into a pound frozen water. When the ice is melted into fluid water, it takes just 1 BTU for each pound to raise the temperature 1 degree. So on the off chance that you have a pound of ice at 32° F, you put 143 BTUs into it to melt it totally. At that point it takes just 180 additional BTUs to raise the temperature of that pound of water from 32° F to 212° F,
The boiling point.
Anyway, returning to our primary discussion, in the event that you have a ton of ice, it takes (143 BTU/lb) x (2000 lbs) = 286,000 BTUs to melt it totally. You could do that in one hour or 10 hours or a year, contingent upon how rapidly you pump heat into it. Some place along the line, however, somebody chose to utilize 1 day—24 hours—as the standard time reference here. In the event that the ice softens consistently over the 24 hours, it assimilates heat at the pace of 286,000/24 hrs = 11,917 BTU/hr.
Gathering that number together makes it a pleasant, round 12,000 BTU/hr. In air conditioning, at that point, a ton of AC capacity is equivalent to 12,000 BTU/hr. There it is.
In case you’re thinking about how this term got institutionalized, it was most likely the typical way. People in the business begin utilizing it, and after that the expert associations make it official. An architectural site a statement from 1912 that claims the American Society of Mechanical Engineers standardized it.