Let Manuals J and D Guide Your Next HVAC Installation

Posted On: June 06, 2013

Are you hoping to enjoy the benefits of a high-efficiency HVAC upgrade? In order for your equipment to achieve maximum efficiency, your contractor should be well-versed in Manuals J and D. Here’s a look at why these tools are so important and what you should expect from your contractor throughout the process.

What’s the big deal with Manuals J and D?

When it comes to heating and cooling equipment, size matters. For obvious reasons, a system that is too small for your home’s needs will be unable to provide adequate cooling or heating. Unfortunately, an oversized system can create even more problems. When HVAC equipment is too big for your space, it will cycle on and off frequently. Not only does this waste energy, it also puts excessive strain on your system. Additionally, oversized air conditioners are unable to adequately remove moisture from a home’s air. This can lead to problems with mold and mildew.

In an effort to add precision to the sizing process, load calculation tools were developed by the Air Conditioning Contractors of America (ACCA). Manual J enables your contractor to determine exactly how much heat your home needs during the winter, and how much warm air and humidity must be removed from your space during the summer. Manual D, on the other hand, is utilized in evaluating ductwork. This enables HVAC professionals to determine the size and layout necessary for your ductwork to be compatible with your new heating or cooling system.

How do load calculations work?

Achieving precision in Manual J load calculation is of the utmost importance. Not only does it assist in the sizing of your equipment, but it also plays a role in duct sizing, as Manual D is based on Manual J load calculations. In order for accurate results, your technician must consider a number of factors including:

  • Local climate
  • Home size in cubic feet
  • Number and type of windows
  • Location/orientation of windows
  • Insulation values
  • The home’s airtightness
  • Landscaping considerations
  • Heat-producing appliances
  • Number of household occupants

Often, these factors can be adjusted or mitigated by a homeowner (such as adding insulation or sealing air leaks), allowing for  a smaller and less expensive HVAC system.

To learn more about Manual J and D load calculations, contact the professionals at Ernst Heating & Cooling. We are proud to serve residents of the Edwardsville, Collinsville and Maryville, Illinois area.

Our goal is to help educate our customers in Edwardsville, Collinsville, Maryville, Highland, Greenville, and Troy, Illinois and surrounding areas about energy and home comfort issues (specific to HVAC systems).  For more information about sizing your next installation and other HVAC topics, download our free Home Comfort Resource guide. 

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The technician, Dan, was very thorough and informative when he did a summer tuneup on my AC.
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