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Manual J: Why Your Contractor Should Know It From A To Z

June 19, 2012 | Blog

When it comes to your air conditioner, size matters. As you work with your HVAC company to install your new climate control system, they should understand how to properly size your air conditioner using Manual J. This calculation tool was developed by industry experts to determine the specific cooling needs of individual homes. Here we will explore the reasons why it’s important that your contractor understands  proper load calculations when sizing your air conditioning equipment.


Having over-sized air conditioning equipment installed in your home is inefficient and unnecessary. Not only is an air conditioner that’s too big a waste of energy, but the system will have a difficult time providing even cooling to the rooms in your home. Making sure that your installation company calculates your needs with Manual J will lower your utility bill and increase the efficiency of your air conditioner.

Air Quality

One problem with a system that’s too big is that it cannot properly dehumidify your home or filter its air. This is because an over-sized A/C tends to cycle on and off frequently, and more continuous operation is necessary for proper air filtration and humidity control.


You’ll achieve maximum comfort from your climate control only when your air conditioner is properly sized to the sensible and latent cooling loads of your home. In layman’s terms, this means that using Manual J calculations, your HVAC professional can determine the exact amount of heat and humidity that your air conditioner will need to remove from your home.

As you can see, having a new air conditioner installed is more complex than randomly picking the equipment that “looks good” or that matches the size of your old system. Most air conditioning systems are oversized.  If you have done anything to make your home more efficient like new windows, more insulation, sealing air leaks, or anything like that then your Air Conditioning equipment is even more oversized.  Having a qualified, professional HVAC technician calculate your exact cooling loads will ensure that you’ll get the most value and comfort from your climate control system.

For more expert advice on Manual J and other matters related to home comfort, please contact us at CCAC, Inc. We proudly serve the Coastal Bend.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).  For more information about the Manual J and other HVAC topics, download our free Home Comfort Resource guide.

Mathews CCAC Air Conditioning and Heating services Corpus Christi, TX. Visit our website to see our special offers and get started today!     

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