Thanks to climate change, summers are getting hotter. Keeping commercial buildings comfortable will become more difficult in the coming years. The HVAC unit may no longer be up to the cooling challenge as ambient temperatures peak well above 100 degrees Fahrenheit worldwide. That reality will necessitate air conditioning system upgrades. Performing a commercial load calculation is essential for getting the best results when updating a building’s air conditioner.
Why else are commercial load calculations necessary when upgrading a building’s HVAC unit? What goes into load calculations?
What Impacts Building Cooling Load?
Many things can impact a building’s cooling load, affecting the energy it takes to keep the building cool in the summer or warm in the winter. Explaining to a client that the commercial load calculation can affect resource usage is an excellent way for the contractor to make this part of the AC upgrade seem more relevant to customers. The cooling load factors can include:
- Directional orientation: The direction of a building’s face and the number of windows on each can impact the cooling load.
- The number of windows and the direction each faces: Builders can mitigate this factor by installing energy-efficient multi-pane windows.
- Energy efficiency: This is often affected by how well-sealed the doors and windows are.
- Local climate: The closer a building is to the equator, the higher its cooling load becomes.
- Condition of ductwork within the building: Poor or insufficient ductwork will interfere with airflow. Even if the installed had properly sized the HVAC, the air needs somewhere to flow.
- Landscaping: trees and other native flora can help to reduce the amount of direct sunlight the building gets, thus reducing the building’s cooling load.
When HVAC contractors meet with decision-makers to discuss their commercial cooling needs, everyone involved in the associated conversations needs to consider these points. The answers will enable an informed conclusion about the size of a commercial building’s HVAC system.
What Goes Into a Commercial Load Calculation?
Calculating commercial HVAC loads is similar to doing the same calculations for a residential structure on a larger scale.
Start with the square footage of the building. Note that these calculations are for buildings with standard eight-foot ceilings. Anything higher than this will require additional measurements. Next, divide the total square footage by 500, then multiply that answer by 12,000. This total is the minimum number of British thermal units — or Btus — necessary to cool the space successfully.
The calculations continue there. Each person who will work in the space adds an extra 380 Btu to the analysis. Contractors should ideally get the current number of building users as well as any plans to expand the workforce size. However, a general average is sufficient if building operators are unsure about the number of regular employees on staff.
Windows add 1,000 Btu and kitchens add an extra 1,200 Btu to the calculations. Finally, divide that total by 12,000 to determine the total tonnage necessary to cool the space.
Adopting Load Calculation Software
As long as contractors have a calculator and enough time, they can do calculations by hand. However, determining load calculations for an entire building can be more challenging. Instead of manually keeping track of all the math and measurements, HVAC contractors can automatically adopt load calculation software to do all the heavy lifting.
These programs come in various styles — some designed to run on desktop computers or in an internet browser, while others are for use on an iPad or other mobile device that HVAC technicians can take on the road. Getting used to using them may be a bit of a learning curve, but it should save time and increase accuracy for the contractor, which improves outcomes for clients.
For companies that have been making these calculations manually in the past, the Air Conditioner Contractors of America has a list of ACCA-approved software options that can budget these business owners in the right direction.
Why Are Load Calculations Important?
Load calculations might seem pointless to the outside observer. Instead of worrying about math, opting for the largest unit that fits the budget might seem better.
Unfortunately, advising a client to select the biggest HVAC unit without carrying out a commercial load calculation can have devastating consequences. In the best-case scenario, improperly sized HVAC units can drive up utility costs and wear out faster due to excessive use.
That could mean contractors have to go to more service calls at a client’s building and listen to how they’re unhappy with the overall operating expenses. In the worst-case scenario, oversized units can cause premature transformer failure, leading to expensive repairs, regulatory fines, civil lawsuits or worse.
Undersized HVAC units will have to keep operating at all times to cool a space and may not be up to the job. This perpetual operation will increase utility bills and the building’s carbon footprint. It will cause premature wear and tear, which can add to operational costs in the form of repair or replacement. These units will also likely create poor airflow and sections of the floorplan will almost always be too warm or uncomfortably cold.
When a contractor’s clients adopt a “bigger is always better” mindset, such beliefs create opportunities for HVAC professionals to explain that oversized units aren’t a better option and discuss the resulting ramifications. These units will cycle on and off more frequently than necessary. This rapid transitioning will cause hot and cold spots within the building and leave behind excess humidity leading to condensation, mold or mildew buildup.
Turning on and off too frequently can damage the system, causing it to burn out faster. Similar to undersized units, these oversized options will waste energy and increase the structure’s carbon footprint.
Make a Commercial Load Calculation Part of Every AC Upgrade
Suggesting that a client go with the largest HVAC unit or installing one too small for the building in question can cause negative results that can frustrate clients and hurt a contractor’s reputation. Commercial load calculations are essential to ensure that the building is comfortable, the HVAC units aren’t overworked and the transformers don’t take damage because of improperly sized units.
HVAC contractors should put themselves in the position of commercial building decision-makers by realizing that these individuals primarily want to protect their investments. Doing that might require paying more for a larger HVAC unit or a reinforced transformer, but that initial investment will end up paying for itself in the long run. A proper commercial load calculation ensures a unit can do its job correctly without suffering undue wear and tear or breaking down prematurely.
Emily Newton is an industrial journalist. As Editor-in-Chief of Revolutionized, she regularly covers how technology is changing the industry.
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