This calculation is called a "Manual J." Salespeople don't usually do load calculations, though. What furnace size makes the most sense? Well, the HVAC company should perform a load calculation to determine what size is best for your home. You can go either way, but the option isn't always reflected in a supplier's price book. The thing is, that same 3-ton AC might also pair with a 60,000 BTU furnace. If you consult the price book, you might find that a 3-ton AC pairs with an 80,000 BTU furnace. The book includes matchups for different system components - ACs, furnaces, and coils. An HVAC salesperson carries a price book from an equipment supplier. Most HVAC salespeople don't understand HVAC design.īeing good at selling HVAC equipment doesn't make you good at selling the right HVAC equipment. So, why are so many systems oversized in spite of these crippling problems? Let's explore the most common reasons. They actually make you less comfortable - not more. That's why oversized HVAC systems are best avoided. And if your bed is right under a vent, you feel like you're sleeping inside a volcano. As a result, you have hot and cold spots throughout your home. An oversized one blasts you with scorching hot air and satisfies the thermostat right away. A properly sized furnace can give you that. In winter, you want consistent heat throughout your home. Oversized furnaces turn your home into a scorch chamber.Oh, and subpar dehumidification leads to subpar indoor air quality. The bottom line? You're hot, sweaty, and uncomfortable - even though the thermostat says you shouldn't be. So even though that oversized AC brings your home down to 73 degrees really quickly, it has a hard time keeping your relative humidity below 60%.
Longer AC cycles are more effective at clearing out humidity. All that extra tonnage cools your house down very quickly, so the AC cycles are short. Oversized air conditioners don't dehumidify very well.Bigger HVAC equipment isn't better because… There are actually proper tonnage (air conditioning) and BTU (heating) sizes for every home. Isn't bigger HVAC more powerful and, therefore… better? In fact, it's unusual that a week goes by that we don't encounter a system that's too big for the house it's tasked to cool and heat. Big problems, small problems, unusual problems, trivial problems, expensive problems… You name it, we've seen it.Īnd oversized systems are among the most common HVAC problems in our area. After more than a decade spent exploring Atlanta's residential HVAC scene, we've seen just about every problem you can imagine.