Hansberger Refrigeration Blog: Your AC Repair Resource

Manual J and Manual D: Is Your Contractor Thoroughly Versed?

If you’re planning an HVAC update and are considering contractors, you’ll want to make sure they employ Manual J and Manual D software in calculating your home’s cooling and heating loads. Then use that information to size the new system thus making sure ductwork is compatible. These software tools were developed by HVAC professionals to take the guesswork out of system sizing and installation. A contractor who briefly visits your home and goes by the size of the existing equipment could set you up for higher energy costs, less indoor comfort and more maintenance expenses down the road.Manual J and Manual D: Is Your Contractor Thoroughly Versed?

Sizing new conditioning equipment is a critical step in the replacement process. A system that is too large for your home wastes energy, leaves more humidity behind and may require more frequent repairs. These systems run for brief periods more often, which drives up electricity use. The power load is highest at start-up, and this is when the most wear on the parts occurs, wearing them out faster. On the other hand, a system that’s too small won’t be able to adequately condition your home during hot weather (which is much of the time in Southwest Arizona).

The first step when using Manual J and Manual D is the Manual J load calculation, which takes these attributes of your home into account:

  • Cubic footage;
  • Windows, their orientation to the sun and energy efficiency;
  • Insulation in walls and attic;
  • Air leaks in home’s envelope;
  • Types of lighting;
  • Heat-producing appliances;
  • Household size and ages;
  • Preferred indoor temperatures; and
  • Landscaping factors.

Once the technician calculates your home’s cooling load, he can size your home’s new system and then use the results as the basis for performing the ductwork analysis using Manual D. This software helps the contractor make sure that the ducts are properly designed and sized for the HVAC equipment. If the ducts are too small, they’ll be noisy, and when they’re too big, the air won’t move with enough velocity to reach all of your rooms.

The contractor should also thoroughly inspect and test the ducts for leaks. Tight and well-designed ducts help you get the most from your new system.

For more information about Manual J and Manual D, please contact us at Hansberger Refrigeration & Electric Company. We’ve provided exceptional HVAC services for the Yuma area since 1952.

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

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