Manual J: Make Sure Your Technician Uses It When He’s Sizing Your New System

When you’re choosing a new HVAC system this summer, you can rest easier when you know that your HVAC contractor is using Manual J. This tool is the industry standard for calculating the size of the cooling and heating equipment you need for maximum comfort and lower energy bills.

Going by the size of your existing equipment is misleading, since improvements to your home can alter its conditioning requirements. Systems that are too large use more energy, cost more initially and don’t work as well, particularly for cooling. If an air conditioner is too large, it doesn’t run long enough to remove enough indoor humidity for optimal comfort. It also comes on more frequently, which increases your electric bill and the wear and tear on the whole system.

Manual J takes into account factors related to your home, including:

  • Cubic footage that requires conditioning.
  • Insulation levels.
  • Air infiltration rates.
  • Size and quality of the windows, along with sun exposure.
  • Appliances that emit heat and your lighting type.
  • Outdoor landscaping.
  • Number of people living in the home and their ages.
  • Preferred temperatures.
  • Lifestyle considerations.

In addition, the HVAC technician takes into account the style of your home. Open floor plans have different heating and cooling demands than homes whose rooms are separated by walls.

Since the climate in San Antonio is humid in the summer, the technician also factors in the highest temperature and humidity the new system has to manage. The latent cooling load considers humidity needs, while the sensible cooling load takes into account the highest temperatures to which the air conditioner has to respond. (The technician considers the coldest temperature at night that the furnace encounters during the winter to establish the heating load.)

When you have the results of Manual J, you can make improvements to insulation levels, seal the leaks and cut the amount of heat entering or leaving your windows to improve efficiency. This will reduce the equipment size you need and lower your energy bills.

If you want more information about Manual J or HVAC system selection, contact Beyer Boys. We’ve provided HVAC services in the San Antonio region since 1990.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).

Beyer Boys services San Antonio, TX. Visit our website to see our special offers and get started today!

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