Depending on what type of system, the weather and how well your system functions within your home can ultimately dictate how often your system turns on and off. What do I mean when I say, “how well the system functions within your home”? As you may already know all houses are constructed differently, with different types of building material, insulation, windows, directions the home faces, and square footage. All of these are factors when comes to properly size your system.
Example: If on one hand, you have a 1,000 sq ft home with nothing but windows facing the north side and another home (same size) with windows facing the west side, what house do you think might become warmer in the afternoon during the summer? Or how about the winter? With this scenario, this house could need a slightly different-sized AC or heating unit just based on the direction the windows face. This is just a small factor of how a system can be correctly or incorrectly sized.
I’m sure you are familiar with the new “yeti coolers” expensive however, they are extremely insulated enough to hold ice for nearly a week compared to most coolers that might hold ice for hours. This is the perfect example because the insulation in your home is very much like this cooler. The type and amount of insulation you have in your attic, the longer the heat or cold air stays within your home. What separated Yeti from other competitors is they use foam insulation to insulate their coolers. Foam is also starting to become even more popular inside residential homes and commercial buildings. People with foam-sealed attics usually only have a 5–10-degree difference between the temperature in their home and the attic temperature. If you’ve ever been in an attic during mid-summer, you might expect your attic to reach temperatures as high as 160 degrees! This could mean that compared to foam you could have a nearly 80 degrees temperature difference. The amount or type of insulation can factor in how large or small your system needs to be to properly condition your home efficiently.
To ensure your system is the right size is actually very easy and takes little to no time at all. There are many different types of calculations when it comes to your entire HVAC system and if not done properly you could have higher than normal electric bills, high humidity, and even mildew/mold. We recommend before you change any system out, perform a Manual J, Manual D and Manuel S. The Manual J calculation will tell you if your system is properly sized for your home based on most of the conditions we discussed above. In a nutshell, you want your system sized to cool your home on a 105-degree day to 75 degrees with relative humidity below 30 percent. Now we know in Texas, it can get pretty darn hot but usually, it’s not for long, we might only see it reach 105 degrees for maybe 2 months out of a year. Does this mean your system is sized for only 2 months out of the year? You got it, your system is actually oversized when the temperature is anything below 105 degrees. Now if we sized your system for more of the average temperature which would be anywhere from 80-90, your home would be miserable when temperatures did reach over 105 degrees because this system wouldn’t be large enough.
Your system might be sized correctly depending on what type of system you have. To boil it down, there are 3 different types of AC units. You have a single-stage unit that only turns on and off full blast with one speed, a 2-stage unit that can operate at 65% of its total capacity with 2 speeds, and then you have a variable inverter that can have as many as 300 speeds. Like most things you invest in, the more you spend the more you get, but how do you know if it’s worth it or not?
To determine how many stages your system has, go outside to your condenser/heat pump and look for the data plate sticker, this is normally located near the service valves or access door on your condenser. Take a picture of the model number and look it up online.
Typically, if you had a Manual J calculation done, you would have witnessed the system design specialist walk around the house with paper, a pen, and some type of measuring tool. Typically, you would see a drawing of your house (very much like a blueprint) with what type of windows, how many window blinds, insulation, ceiling height, the direction of the home, infiltration measurement, radiant barrier, and square footage of the home. This calculation will tell the homeowner exactly what size system they need.
Unfortunately, because this calculation takes time, most contractors skip this step to save time and money. It’s very common for contractors to come in a just replaced the system with the same tonnage that’s already there. The problem is if the calculation wasn’t done, to begin with, the system could have been over or undersized since day one. But if the contractor is truly looking out for the customer’s best interest, spending the extra time to complete this measurement will protect customers’ large investment and save them thousands down the road.