The Importance Of J Load Calculations

In today’s world, almost everything seems oversized. We go to Starbucks and buy a venti coffee instead of a tall one because we assume we’ll need the extra caffeine. We buy two new titles in our favorite series instead of one because we don’t know if we’ll find both in the same bookstore again.

HVAC systems are not much different. People inadvertently buy oversized HVAC systems all the time out of a belief that bigger is better. Yet knowing the system size you actually need and calculating its loads correctly could save you money, time, and energy.


What Is A J Load Calculation?

If you’re researching HVAC systems, you’ve probably already heard the phrase “J load calculation.” You know it’s important, but what exactly is it? J load calculations refer to Manual J. This is actually not a manual, but a product. The Air Conditioning Contractors of America (ACCA) use it to size HVAC systems for individual homes. Manual J helps determine how much cooling your home needs, which determines how much energy will be used in the process.

Why You Need A Load Calculation

In the same way you exhibit symptoms when you get a cold, your house will exhibit “symptoms” when you use an oversized HVAC system. One key symptom is an increase in repairs. An oversized HVAC system takes more energy to run, so it will naturally experience more wear and tear than a properly sized system would. Over time, you’ll find yourself spending increasing amounts of money on repairs. Eventually, you may need to replace the entire system even if replacement seems premature.

Additionally, your home’s temperature is a good indicator your HVAC system is too big. Oversized HVAC systems can’t dehumidify the air properly. As a result, your house may feel cold and clammy or unusually stuffy. Worse, humid air increases your chances of allergy and asthma attacks, respiratory illnesses, and exposure to contaminants like mold. If your house feels uncomfortable or you have respiratory symptoms, it may be time to downsize.

Finally, running an HVAC system without load calculations can negatively impact energy efficiency. Some large HVAC systems “kick” on and off arbitrarily, leaving your home insufficiently warm or cool. To compensate, you must constantly adjust the HVAC machines and your thermostat. This wastes electricity and fuel and can contribute to air pollution. In contrast, smaller HVAC systems naturally use less air. Your home heats or cools faster and more thoroughly, and your system doesn’t have to work as hard to use leftover or “wasted” air.

How To Correctly Size Your HVAC System

Professionals should calculate J load for you; do not try to do so yourself. To properly calculate J load, professionals like the ones at McMaster Air will consider how much square footage you have, your insulation levels, and which surfaces gain or lose heat in your house, among other factors.

Even homes that need plenty of cooling often use HVAC systems 2, 3, or 4 times too big. If you are not sure how big your system should be, it’s best to contact McMaster Air and get an exact calculation. To get your calculation or discuss your cooling needs further, please contact us immediately. It’s our mission to ensure your HVAC system keeps your home comfortable, but also uses only the energy it needs.

Fundamentals Of HVACR Industry

Pretty much anyone can read a thermal screen and or tell when an HVACR (heating, ventilation, air conditioning and refrigeration) has stopped functioning. However, the HVACR industry focuses on producing and employing trained technicians, trained by only the best HVAC instructors, to perform the tasks of HVACR installation, maintenance and repair among other tasks. Although many people claim to have the adequate training capacity, it is important to note that any solid HVACR training must always incorporate the fundamentals and the basics of HVAC systems.

Benefits of trained technicians

A trained technician possesses the basic skills of going about any HVAC equipment regardless of its model or the so-called complexities. This not only enables him/ her to diagnose any problem or potential problem with HVAC equipment, but also helps him/ her come up with a viable solution. Additionally, these technicians can be counted on to recommend energy efficient equipment, install them and or conduct regular maintenance and repairs.

Importance of contracting trained technicians for regular HVAC equipment maintenance

New equipment function relatively energy efficiently even if it does not allow much energy saving. With more complex technologies, energy efficient equipment have been made and supplied to consumers, but with time, even the most energy efficient equipment wears off and its energy efficiency reduces. A trained technician, conducting regular maintenance on the equipment, ensures that the equipment receives proper cleaning and minor repairs so that no energy gets wasted. Regardless of the equipment’s manufacturer and or complexity, these technicians can always apply the fundamental basics they learn about HVAC systems to ensure each equipment functions as it should.

HVAC instructors

Most HVAC trainers seek to make their students as skilled as possible. However, some trainers forget about the main purpose of training and train on anything else but the fundamentals of the HVAC systems. Effective HVAC trainers should ensure that as they teach about the complexities of the upcoming HVAC equipment, they teach the students on the fundamentals and basics of HVAC, such as thermodynamics principles, so that they can always employ those skills if anything else fails.


Effectively trained HVAC technicians must possess the fundamentals and basics of the HVACR industry, in addition to whatever else complexities they wish to learn. Basic understanding of the HVAC operation mechanisms enables trainees to work on a wide variety of HVAC equipment regardless of their complexity. The trainees can, thus, detect and correct problems on any HVAC equipment.