Heating and cooling loads are calculations used to determine the proper HVAC size for a home. You wouldn’t waste money on oversized clothes “just in case” you need the extra space, so why buy more HVAC capacity than you need? Unfortunately, many new homes have oversized HVAC systems and other homes may not have enough capacity. For our customers in Goldsboro, North Carolina, we make sure to calculate heating and cooling loads according to the Air Conditioning Contractors of America (ACCA) Manual J.
Understanding ACCA Standards
In the early days of heating and cooling technology, HVAC contractors made educated guesses to figure out a building’s heat gain and loss. The estimate tended to be based on square footage alone without much thought to the building’s construction. For example, contractors would assume a home would need 1 ton of air conditioning equipment for every 400 square feet of conditioned space. After improvements to insulation and window specifications, that figure switched to every 600 square feet. Still, this is a general “rule of thumb” measurement and can’t provide an accurate estimate.
Fortunately, the Air Conditioning Contractors of America (ACCA) was formed in 1968, which helped shape the way we conduct HVAC business. The country’s largest HVAC contractor organization developed industry standards for accurately determining a building’s heat gain and loss. The method involved such a complex system of mathematical equations, however, that many contractors refused to use it.
Thanks to the modern age of computer software, the process has become more accurate and convenient. The software an HVAC technician uses to assess load calculation takes into account the details of a home and how its construction can affect its heating and cooling. The current protocol for determining residential load calculation is referred to as “Manual J.”
What Does a Manual J Calculation Consider?
A Manual J load calculation provides your technician with critical information about your home and how it heats up and cools down. This information includes:
- Heating load
- Latent cooling load
- Sensible cooling load
Heating load is how much heat your home requires on the coldest night of the year. Latent cooling load describes the amount of moisture your system needs to remove during a worst-case scenario, such as during a wet summer day. The sensible cooling load is the amount of heat the system should be able to remove during the hottest day of the year when the sun is out.
When considered together, these loads give the technician an accurate picture of the type of heating and cooling equipment your home needs.
Why Is Load Calculation Important?
You may wonder why it’s such a bad thing to have a bigger HVAC than your home needs. If you like to stay extra cool in the summer and toasty warm in the winter, surely the extra capacity can help, right? Wrong!
Oversized air conditioners can result in a clammy indoor environment because they don’t run long enough to properly dehumidify the air. Since they turn off frequently (a process known as short cycling), the unit experiences a shorter life span from having to switch on so much. Larger units are also more expensive to install.
When you have a unit that’s too small for your home, you run into the opposite problem — the system works too hard trying to keep up with space it can’t possibly accommodate.
When your home’s HVAC system is just right, you enjoy all the benefits a homeowner should, including:
- System efficiency
- Indoor comfort
- Improved air quality
A properly sized HVAC system will keep humidity, odors, and allergies under control. It will also reach your desired temperature and maintain that environment without working overtime or short cycling.
Have you noticed your air conditioner short cycling or failing to cool down your entire home? If so, it may be improperly sized. Contact Carolina Comfort Air at 919-879-2106 to schedule an HVAC appointment with one of our friendly contractors. We can measure your home’s heating and cooling loads using the latest technology to ensure you’re enjoying the best efficiency and maximum energy savings.