Often you will hear HVAC professionals talking about heating and cooling loads. A layman with no prior knowledge of the heating and cooling equipment finds it hard to follow any such conversation. Here, the communication gap is nobody’s fault. The contractor’s only excuse is that they talk in this jargon day in and day out. They often forget that everybody is not familiar with the terms. But, always keep in mind, you can ask your HVAC contractor as many questions as you want until you are completely satisfied.
This article aims to educate you about thermal load, heating and cooling loads, and the associated fundamentals.
Heating And Cooling Loads
Within the HVAC industry, the heating and cooling loads refer to the thermal load, which is the amount of conditioning required by a home or any other closed structure. Herein, the load is the amount of work the system or unit must do to maintain a comfortable temperature indoors.
1. Heating Load – Heating load is the total amount of heat energy added to a zone or an area to sustain the temperature in the permissible range.
2. Cooling Load – Cooling load is the total amount of heat energy extracted from a zone or an area to sustain the temperature in the permissible range.
Are Load And Capacity The Same?
Now that you know what load is, you might think that you’ve already heard about it. Only then, people were referring to it as “capacity.” Well, this is where things get tricky because although the two sound similar, they are, in fact, very different.
1. Load – Load, is what the building or the enclosed structure needs to maintain a steady temperature in an adequate range.
2. Capacity – Capacity is the amount of work that the HVAC can do. In other words, it is the actual heating and cooling that the HVAC can provide.
The next time you hear the word “load,” it means the building’s need, and when you hear “capacity,” it means what the heating and cooling system can provide.
Factors Influencing Thermal Loads
In calculating the Thermal load, the following two factors play a pivotal role:
1. The way your home is built and the quality of insulation used. It includes the complete physical structure, which is the floor, walls, and ceiling.
2. The size, performance, and overshadowing of the installed glazing and skylights in residence.
Types Of Heating And Cooling Loads
The HVAC contractors try to meet three types of heating and cooling loads when they tell you the size or capacity of the heating and cooling system most suited for your home. These are:
1. Design Load – Design here does not refer to the design of the HVAC. Rather, it refers to the design of the residential or commercial building. It means the load calculation is done keeping in mind the design of the structure and the design temperature, which is predetermined. The load calculation considers factors like the structure’s layout, R-value of insulation, the building’s orientation to the sun, outdoor summer and winter design temperature, etc.
Therefore, the design cooling load is the amount of air conditioning you will need when the inside and outside temperatures correspond to the summer design levels. Similarly, the design heating load is the amount of heating you will need when the inside and outside temperatures correspond to the winter design levels.
2. Extreme Load – All places don’t have a moderate temperature. In some places, temperatures can be extreme. The extreme load is the hottest and coldest temperature in the region. The good thing about extreme weather is that it does not last long. The main concern that now comes to mind is whether one should consider the extreme weather while calculating the load.
The extreme load should not be the sole consideration. First, you do a manual J load calculation, which calculates the heating and cooling requirements of the home. This calculation considers the home’s design and has an in-built buffer that caters to extreme weather.
3. Part Load – On any given day throughout the year, you will notice that the extreme temperature (if it does reach) is only for a few hours. For the majority of the day, your heating and cooling equipment works in part-load conditions. Therefore, it will not be remiss to mention that part load is a more deserving consideration than extreme load.
All heating and cooling systems work at a fixed capacity. It means their output is fixed. If you notice, an oversize AC will cool the home faster but will not remove adequate humidity. Similarly, a small size AC will run longer and still not cool the structure. Therefore, part load and design load have more weightage when calculating the thermal load.
Calculating The Thermal Load Of Your HVAC
There are online load calculators available over the internet to calculate the thermal load of your HVAC. However, we strictly ask you to think twice before using one, as even a small mistake while entering the numbers will land you with the wrong result. The HVAC contractors can help you figure out the load. It is always best to rely on their experience and expertise in the matter. Nevertheless, if you must calculate the load yourself, you will need the following information:
1. The area of the house or its square footage. This information can be found in its blueprint.
2. The grade of insulation used in your home or office building.
3. The number of people occupying the house.
It’s A Wrap
For any homeowner or building manager, it is essential to know that load is different from capacity. Where the load is the heating and cooling the structure needs, capacity is the HVAC’s output. For figuring out the heating and cooling loads, and capacity, it is advisable to depend on a professional HVAC contractor.
If you live in West Palm Beach and wish to calculate the thermal load for your commercial or residential building, contact Aztil Air Conditioning. We can also assist you in figuring out the size of the HVAC most suited for your structure. Additionally, you can depend on us for its installation, repairs, and maintenance too. We are your one-stop-shop for all HVAC needs. To book an appointment, give us a call anytime at +1-888-729-8452. We are open 24/7.