Calculating Loads for Commercial HVAC

Published on: January 23, 2016
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Getting accurate load calculations for your HVAC system is important for its design. These calculations depend on several variables, including building size, air tightness, insulation, the climate in South Carolina, and more. You can use them to choose a system that’s the right size for your home or business. A badly sized system could be noisy, uncomfortable, and expensive. Use Air Conditioning Contractors of America or ACCA Manual J specifications for accurate load calculations that will save you money. Here are the factors you should consider when making HVAC load calculations.

Load Assumptions

Most buildings can withstand extreme conditions such as the hottest day of the year or the coldest night of the year. However, designing a system to withstand record temperatures will result in wasted energy. Installers usually assume an average indoor temperature of 75 degrees Fahrenheit and an indoor relative humidity of about 50 percent.

Internal Load

Heat gain is all the heat that flows into a building. Heat gain in commercial buildings is mostly from internal loads such as computers, lighting, and body heat. The internal load also considers locations of ductwork. It will be higher with ducts in a hot, uninsulated attic than with an insulated or ductless system.

Latent Load and Sensible Load

The latent load considers the humidity in homes. Sensible heat removal lowers the indoor air temperature. Most air-conditioners work at a sensible heat ratio between 0.75 or 0.80. The sensible heat ratio is the sensible load divided by the total load. The total load is the sensible load plus the latent load. You can use Manual J computer software to complete these calculations quickly and accurately.

HVAC systems are smaller and less expensive when you use ACCA Manual J specifications for load calculations. Without them, many contractors add bigger heating and air conditioning systems than needed. Contact us at AirConditioningSouthEast.com to find a contractor in your area that can help you to calculate the heating and cooling loads for your home and to save money.