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Understanding Manual J and its Role in Choosing the Best AC Unit

Are you considering an air conditioner upgrade for your home this year? If so, it is essential for you to familiarize yourself with Manual J. Manual J is a tool used by HVAC professionals to determine exactly how much heating and cooling a home needs in order to maintain comfortable temperatures during the summer and winter. It is also often referred to as the Heat Load Calculation or Cooling Load Calculation.

When it comes to your St. Petersburg air conditioning system, Manuel J tells your HVAC professional what the cooling load is for your home. With this determined, the contractor will then be able to understand how much heat will need to be removed from the house by the air conditioner on the warmest day of summer. This will allow him to determine how big an air conditioner your home requires.

There are several factors the technician will need to consider in order to arrive at this final result:

  • The size of your home (measured in square feet)
  • The orientation of your home (direction your house faces)
  • The number of individuals living in the home
  • The number of windows and the locations of those windows
  • Insulation levels in the home
  • Number of appliances that produce heat
  • Local climate

The Importance of Manual J 

While Manual J might seem like a tool that should only matter to the technician installing your air conditioning unit, it is actually essential for you to understand how it works. Why? So you can have the peace of mind that you are purchasing the air conditioning system right for your home.

Purchasing a larger or smaller air conditioner than necessary can result in problems with the following:

  • Efficiency – Purchasing an air conditioner is a lot like purchasing a car. You wouldn’t buy an 18 wheeler if you simply needed the car to go into town to get groceries, would you? No, you wouldn’t. This type of vehicle wouldn’t be considered the best one for the job, plus it would cost you additional money to operate it. The same goes for air conditioners. Just because the unit is bigger doesn’t mean it’s the right one for the job. It simply means you are purchasing a unit that costs more to operate. Because of its bigger fans and compressors, a unit that is too big for your home will cool the house down quickly with a few bursts of cold air. It will satisfy the thermostat, shut down, and then kick back on again when the thermostat tells it to. This stop, start, stop, start type of operation skyrockets your electricity bills.
  • Comfort – Air conditioners generally need to operate for at least 10 minutes before their coils are able to produce condensation. This condensation is what dehumidifies your home’s air. When an air conditioner isn’t the right size, it constantly stops and starts, which does not allow the coils to become cool enough to do their job. During a summer in Florida, this can be a big problem that results in cold, clammy indoor conditions.
  • Air Quality – Because the air conditioning unit isn’t the proper size and is not properly dehumidifying the home, moisture problems often develop and affect air quality. With this problem you’ll often notice excessive dust, mites, mold, mildew, and strange smells.

Understanding Manual J is essential when purchasing a new St. Petersburg air conditioning unit for your home. Talk to your HVAC technician before making any type of AC purchase and make sure you are buying the correct sized unit for the house.

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