Preparing for Your Big Day

Posted on: 28 July 2022

Your air conditioner's capacity (also known as its tonnage or size) refers to its ability to deal with your home's cooling load. Of course, your cooling load is the amount of energy that enters your home due to sunlight, heat transfer through walls, convection, and so on. The more substantial your home's cooling load, the larger the air conditioner you'll need to deal with it.

HVAC manufacturers measure air conditioning capacity in BTUs (British Thermal Units) or tons, which is simply a more convenient unit that produces more manageable numbers. A single ton equals 12,000 BTUs, so a 2.5-ton air conditioning unit has a 30,000 BTU cooling capacity. Since more cooling capacity means more cooling power, it seems logical that more tonnage is better, but is this the case?

Understanding HVAC Cycles

The simple answer is "no," it's rarely a good idea to go big with air conditioners or any HVAC system. However, understanding why this is true requires a little knowledge about HVAC cycles. Your home's air conditioner does not run continuously. Instead, manufacturers design these systems to run in cycles. Cycle lengths can vary, but a well-designed system typically turns on and off several times per hour.

This approach offers a few crucial advantages for keeping your home comfortable and your air conditioning system reliable. Most importantly, it prevents unnecessary wear on mechanical components such as your compressor and blower motor. An undersized system might constantly run, stressing these parts and reducing their lifespan.

However, there are more subtle advantages. For example, your air conditioner dehumidifies as it runs. The cycle time allows moisture to condense onto the evaporator, while the time off allows that water to drain away. An oversized system will run in short bursts, preventing it from adequately dehumidifying your home. You will also be more likely to notice rapid hot to cold transitions.

Choosing the Right Size

While everyone likes to feel like they have some choices, the reality is that there's usually one specific size that's better for any given home. A professional HVAC contractor can calculate this size using a fairly complex formula that will account for your home's overall cooling load. They'll look at your design (or average) load and the more extreme loads you may face in your climate.

This process will result in a BTU figure that should guide your decision when selecting a tonnage for your home's air conditioning system. While exceeding this value by a small amount won't affect your system's overall efficiency, it's critical to keep relatively close to your calculated cooling load. Right-sizing your system in this way guarantees efficiency, reliability, and comfort.

For help choosing and installing an air conditioning unit in your home, contact an ac installation service in your area such as Steele Brothers Heating Inc.