If you’re planning an HVAC installation, it’s important to understand the role that heating and cooling loads play in accurately sizing your new equipment. First, let’s clarify the meaning of two terms that are often misunderstood — “load” and “capacity”. Capacity refers to the output of a particular piece of HVAC equipment, while the load is the amount of heating and cooling output needed to keep your home comfortable. To properly size your new equipment, an HVAC pro takes three types of loads into account:
Your HVAC contractor inputs information about your home into Manual J computer software to calculate the correct equipment size, such as the R-value of the insulation and its orientation. The design conditions are also entered, and these are the seasonal temperatures (indoor and outdoor) for our Northwest Arkansas climate. The “design load” is the HVAC equipment’s output that’s arrived at based on these local design conditions. Your home probably won’t meet these conditions often, but they’re a valuable guideline for sizing the equipment properly.
Although Northwest Arkansas has a temperate climate, wintertime lows can reach 26 degrees. Summers here are humid and hot, and the thermometer can hit 90 degrees. These wide temperature variations are the extreme load conditions your home’s HVAC equipment may have to cope with. If the equipment output was calculated based on these extremes, though, you’d end up with an oversized, inefficient HVAC system. Instead, Manual J software adds 15 – 20 percent to the design conditions to keep your home comfortable during extremes. To lessen the equipment’s load and boost your comfort, it’s vital to make sure your home is well insulated and properly sealed to stop air leakage.
The full capacity of your HVAC equipment isn’t needed roughly 99 percent of the time because the outdoor temperatures don’t meet the design conditions, so it operates at part load. Since HVAC equipment typically has a fixed output, you’re more likely to experience temperature variations and poor humidity control when it’s running under part load conditions. Having a whole-house dehumidifier installed or upgrading to variable-speed technology are two options to solve these issues.
To learn more about how heating and cooling loads factor into your HVAC installation, contact us today at Paschal Heat, Air & Geothermal.
Our goal is to help homeowners in Northwest Arkansas understand the different HVAC-related issues that can affect their comfort and energy bills.