What does AC Tonnage mean in regards to air conditioning?
AC tonnage is a rating system that measures air conditioner capacity. When you hear the word “ton” it’s immediately associated with weight, right? In the HVAC industry, it means something completely different. It actually has to do with the amount of hot air removed by the unit. Think about this – when you’re outside next to a condenser coil and fan, all you feel is hot air. That’s the energy absorbing the heat to help the inside of the building remain cool.
AC Tonnage Defined
AC Tonnage is used to rate an air conditioning unit. It basically determines how many British Thermal Units, or BTUs, of heat can be removed from the internal space within an hour. The higher the ac tonnage rating, the more air it can cool. A normal home needs about one ton for every 400 to 1,000 square feet. That also depends on how the space is configured – windows, ceilings, appliances, sunlight and other factors. It is best to get an energy efficient unit to help save money.
Determining the amount of AC tonnage you need
How do you know how much tonnage you really need? Using a tonnage calculator can help determine how much you need for a single room, or an entire house. The calculator will take the length and width of the room, how many people will be utilizing the space, how many lights are there, the wattage of the equipment, shading, location and size of windows. Then it will calculate the estimated tonnage needed to cool that space.
If you don’t have a calculator, you can do attempt to do it yourself. For example, take a 2,000 square feet with 10 windows and 2 exterior doors that will be occupied by 4 people. This calculation should help:
2,000 x 25 = 50,000 base BTU
4 people x 400 = 1,600
10 windows x 1,00 = 10,000
2 exterior doors x 1,000 = 2,000
50,000 + 1,600 + 10,000 + 2,000 = 63, 600 Btu
63,600/12,000 = 5.3 estimated tons
How do I know how much AC tonnage my HVAC unit has?
Most manufacturers have the amount of tonnage listed on the sticker. In most cases, it is included in the model number of the unit. Look for the model and serial number. There is usually a section that indicates how many thousands of BTU/hour the unit moves out of the space.
When looking at the model number, the first section indicates the type and efficiency of the unit. There are about five characters. Once you get past those, you should see the tonnage. It may look something like XXXBTU/hr. 12,000 BTU/hr is one ton of air conditioner capacity, so you should be able to do the calculations from there.
How important is selecting the right tonnage?
You always want to have the right tonnage for your space or you will waste money. The last thing you want to do is have a unit that cannot properly cool the space, or one that is much larger than what you need. In both cases, the efficiency is lost. An air conditioning specialist can help you determine which type of unit and tonnage you need to remain comfortable throughout the year.