What Is A HVAC Ton…
Simplified, Explained, And Defined!
Have you ever approached a condenser coil section outside of a home or business when the fan is operating? You will discover the fan is blowing hot air. Why… because Air Conditioners (A/C) don’t produce cool air, they remove heat from a space by using refrigerant to absorb heat and transfer it outdoors.
The “ton” reference of an air conditioner’s capacity is related to heat removal, not the amount of air moved through the unit, or its actual weight.
Before electric air conditioners, homes were cooled with blocks of ice. The ice absorbed heat from the building and melted accordingly.
How Much Heat Energy Does It Take To Melt An Entire Ton Of Ice?
It takes 286,000 BTU’s (British Thermal Units) to completely melt 1-ton of ice. A BTU is the amount of heat required to raise the temperature of 1 pound of liquid water by 1 °F at a constant pressure of one atmosphere.
Depending upon the quantity of heat energy the ice encounters, a ton of ice will melt at any given time interval. I discovered an article from the American Society of Mechanical Engineers. According to the article, in 1912 the society appointed a committee which chose 24 hours as the standard time duration for engineers to calculate the energy required to completely melt the 1-ton of ice.
Just Some Minimal Math!
Now that we understand how much energy is required to melt our ton of ice over an entire day, I’ll explain how to derive the industry reference for every A/C unit on the market. Divide 286,000 (amount of energy to melt a ton of ice), by 24 (hours in a day), the result is 11,917 BTU’s of energy per hour to melt the ton of ice.
The industry rounded up to 12,000 Btu/h to reference 1-ton of air conditioner capacity. Therefore, a 2-ton A/C unit will remove 24,000 BTU’s of heat per hour; a 3-ton A/C unit will remove 36,000 BTU’s per hour and so on.
Are Heating and Furnaces Measured In Tons Similar To Air Conditioners?
Heating units are not measured in tons as A/C units. Heating capacity is referred to in 1000`s of BTU output per hour of operation.
Heating units often offer two sets of BTU ratings. These numbers offer the input, and output BTU rating allowing us to easily understand the efficiency of any heater or furnace.
Example; if your home furnace is rated at 100,000 BTU/h input, and 80,000 BTU/h output, when you divide 80,000 BTU (output) by 100,000 BTU (Input), your result is 0.8 (move the decimal two places to the left) or 80% efficient.
Extracting Unit Tonnage From Manufacturers’ Model Numbers
With a basic understanding of BTU to tonnage, interpreting the tonnage from model numbers just got easier. Most manufacturers’ model numbers incorporate the BTU equivalent into their unit model numbers, or reference the tonnage. It’s not an exact science, but understanding tonnage designations provides an educated guess when working with unfamiliar model numbers.
Below are examples of how the BTU equivalent of a unit is often portrayed and incorporated into a model number;
Trane Unit YCD180F – The actual BTU for this unit is 180,000, but is truncated down to 180. Therefore, simply divide 180 by 12 (12,000 reduced accordingly) to discover this is a 15 ton unit.
Bryant – 574D030 – Again the BTU is truncated to 30. This is a 2.5 ton unit.
Other manufacturers incorporate the tonnage directly into their unit number. However, they usually don’t include the precise tonnage. My thought; because of the 2.5, 7.5 and 12.5 ton units which if expressed with whole numbers would cause confusion. Most all manufacturers when referencing tonnage round up.
Carrier: 48TC16 is actual their 15 ton unit.
York: ZX04 – is a 3 ton unit.