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Commercial Load Calculation

Over time, the likelihood increases that you'll need to upgrade the air conditioning system in your commercial building. To make sure your air conditioner upgrade will fulfill the cooling needs of your facility, your HVAC professional should conduct a commercial load calculation.

What is a commercial load calculation?
All buildings, commercial or residential, have a load, which is the amount of heating or cooling that's required to keep the building's indoor comfort at the level preferred by its occupants. A commercial load calculation is a process for determining the exact size of your facility's cooling load and, from there, how much heating or cooling it needs.

Why have a load calculation?
When you know your facility's cooling load, you'll be able to properly size your new air conditioning system. Sizing doesn't refer to the physical dimensions of the equipment, but rather its cooling capacity. By finding out your facility's cooling load and using that information for correct A/C sizing, you'll be able to choose and install air conditioning equipment that will precisely meet that load and control indoor temperatures in your commercial facility.

Correct sizing is important for two main reasons:

  1. If the replacement air conditioning system's too small, it won't be able to cool your indoor spaces properly. Components are likely to wear out early from overuse, and the entire system is more likely to break down and need expensive repair. The useful life of the system will be shortened considerably, leading to the need for another upgrade or replacement sooner than necessary.
  2. An A/C upgrade that's too large, on the other hand, will produce more cooling than needed and will waste energy. You'll end up paying for unnecessary cooling. In terms of indoor comfort, an oversized air conditioner won't be able to remove sufficient amounts of humidity.

In short, proper sizing of your commercial A/C upgrade influences three of the most important elements of HVAC systems: indoor comfort, energy usage and monthly expenditures. By having a commercial load calculation performed by a qualified HVAC professional, you'll be able to choose equipment that will provide cooling that is effective, efficient and economical.

Commercial load calculation references
A commercial load calculation requires a careful inspection of your commercial facility to determine its physical and thermal characteristics. The cooling load of any building can be affected by factors such as:

  • Directional orientation
  • Number and placement of windows
  • Building seal and overall energy efficiency
  • Condition and efficiency of ductwork
  • Local climate
  • Landscaping

Once these factors have been identified, the evaluator can turn to authoritative references that provide detailed instructions on how to assess the influence of these factors and calculate the amount of cooling needed for your facility.

  • Manual N: Manual N, "Commercial Load Calculation," is probably the most widely accepted source of instructions for performing load calculations on commercial facilities. This authoritative manual is published by the Air Conditioning Contractors of America (ACCA), one of the leading professional organizations in the HVAC industry. Manual N covers commercial buildings up to three stories in size. It takes into account the most recent advances and developments, including new materials, functional system requirements and manufacturing methods. It provides all of the background information and technical procedures needed to conduct an effective load calculation. Using the information in Manual N, HVAC professionals can conduct either a basic load calculation or an exhaustive computer-based calculation.
  • Other software: Other industry sources, such as ASHRAE, offer computer software for conducting commercial load calculations. ASHRAE's Right-CommLoad software, for example, uses the ASHRAE Handbook of Fundamentals as its basis and provides easy-to-use date entry screens that help simplify the load calculation process.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection and Alarm Systems in Mechanical, Commercial and Residential settings. For more information on commercial A/C replacement and how Manual N is used to perform cooling load calculations, or to view projects we've worked on, visit our website!

Image Credit: Brian J. Matis

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