Do you know what size your air conditioner is? In the world of building science, you'll hear a lot of talk about why oversized air conditioners are a bad idea. Briefly, they may not dehumidify as well, short-cycling wears them out quicker, and your home will probably be less comfortable if the air conditioner is too big. But to know if your AC is oversized, first you have to know what size it is. (Note: This article is about finding the size of your existing AC, not determining what size you need.) Look for the label The good news is that most HVAC manufacturers make it easy to determine the nominal capacity of your air conditioner. It's in the model number. Go outside and find the outdoor unit, that metal noisemaker hidden away on the side or the back of the house. It'll look something like the one you see above, although maybe not quite so decrepit as that one. Then find the lable that gives the data about your AC. It'll look like the image below. Up near the top of the label, you see the model number (M/N) and serial number (S/N).

The model number is where you can find the number you're looking for. ac unit not draining waterNot all manufacturers do this, but most will give you a 2 or 3 digit section that tells you how many thousands of BTU/hour your air conditioner can move out of your home.why is my ac unit freezing The first section in the model number gives you info about the type and efficiency of the unit you're looking at. how much power does a 3 ton ac unit useIn the case of this Lennox model (which, by the way, is not from the outdoor unit shown at the top of this article), the 13HPX tells you it's a heat pump with an efficiency rating of 13 SEER. The digits you need Just past that string of 5 characters, though, is the part that tells you the nominal size: 048.

That means the air conditioner—or heat pump in cooling mode in this case—has a nominal capacity of 48,000 BTU/hour. I say nominal because the actual capacity is almost certainly going to be different. The numbers you'll see on residential air conditioners and heat pumps are: The 3 digits in the model number tell you the nominal capacity in thousands of BTU/hr. Since each 12,000 BTU/hr is equivalent to 1 ton of air conditioner capacity, it's easy to figure out how many tons of nominal capacity your AC has. Why Is Air Conditioner Capacity Measured in Tons? 3 Reasons Your 3 Ton Air Conditioner Isn't Really 3 Tons Why an Oversized Air Conditioner Is a Bad Idea NOTE: Comments are moderated. Your comment will not appear below until approved.Choosing the type and kind of central air conditioning system to install in your home's heating ventilation and air conditioning (HVAC) system is complicated. There are many physical factors about your home's cooling at play that directly affect the performance quality, efficiency, and the cost of how well a central air conditioning system will work in your home.

You also must consider the wide variety of central air conditioning systems, as well as their size, efficiency, and installation requirements. So, it's no wonder that homeowners can get anxious when they want to know what size air conditioner they need for their home. Central air conditioning uses a compressor and condenser coil housed in an outside unit and an expansion valve and evaporator (also called an "A coil") mounted above the furnace heater inside your home's HVAC system. Air conditioning works by cycling refrigerant from gas to liquid and then to gas again through the use of pressure. The refrigerant (known as R-410A) begins the cycle as a low-pressure, low-temperature gas. It enters the outside unit where it's first compressed into a high-pressure, high-temperature gas. Next it enters the condenser's coil where the fan cools the gas into a high pressure liquid. The liquefied refrigerant flows through tubing inside your home to the HVAC unit. There it first enters the expansion valve which limits the flow of the liquid as it enters the evaporator.

This valve lets the liquid expand inside the evaporator coil into a gas, chilling to about 7 degrees Celsius as air from the HVAC blower moves over the coil. The refrigerant then heads back to the outside unit as a low-temperature, low-pressure gas to begin the cycle again. Air is cooled by being blown over the chilled coil, and it's then circulated throughout your home. The AC system continues running until the desired temperature is reached. Any humidity in the air condenses onto the coil as water and drips into a condensation pan. In this way, your home is both cooled and de-humidified by a central air conditioning system. Choosing the correct size of your air conditioner is a key a factor for setting up a home cooling system. Sizing an air conditioner requires a consultation with a professional Energy Management Consultant who looks at the factors that effect your home's cooling: Likewise, it's not a simple matter of dropping-in any air conditioning system. The size is very important because the correctly sized air conditioner should run a proper full cycle and ensure your home stays cooler longer.

An over-sized AC system will quickly over-cool the air in your home and shut off too soon. However, the building structure itself (walls, wood, furniture, etc.) will not be cooled adequately and allow heat and humidity to creep back in, and the AC will kick-on again and again. As a consequence, over-sized systems run for too short a time far too often. And it can cost you far too much. An undersized system, however, will not effectively cool your entire home. It will run continuously, waste energy, and wind up costing you more. Air conditioner sizes are rated in tons of cooling capacity. One ton of cooling is equal to 12,000 BTU's (British thermal units) per hour. For example, a typical residential unit is a 2-ton unit that cools 24000 BTU/hour and a larger 3-ton unit cools 36000 BTU/hour. While two air conditioners be the same tonnage, they could be completely different in terms of their energy efficiency or Seasonal Energy Efficiency Ratio(SEER) . Once you have found the right tonnage-size to cool your home, you'll want to look over which ones have the best SEER rating as is practical within your budget.