First Step in Air Conditioner Replacement: A Load Calculation

by Greg Leisgang on April 22, 2013

Posted in: Air Conditioners

load calculation, Greater Cincinnati, OhioThe first step in replacing your central air conditioner should always be a load calculation. The calculation determines the precise size for the A/C equipment and it takes into account many variables about your home's ability to resist heat gain.

Cincinati HVAC contractors use a tool called Manual J to start the calculation, and running the numbers first may help you find the places in your home that make it harder to cool. 

Manual J takes into account these properties of your home to find your cooling load:

  • Cubic footage
  • Insulation levels in walls and attic
  • Windows, their exposure to the sun and efficiency
  • Air infiltration rates
  • Preferred indoor temperatures
  • Number of home occupants and their ages
  • Heat-producing appliances
  • Landscaping factors

When the load calculation is the first step in the selection process, you can learn how improving your insulation levels and sealing the air leaks in your home could help you select a smaller air conditioning system. Not only will it cost you less initially, your cooling bills will be lower for years to come.

After the HVAC contractor assesses the cooling load based on home features, he or she then evaluates your existing ductwork system and its size, using Manual D. Sealing and insulating the ductwork will also help you lower your cooling bills, since thermal or air losses in the ducts contribute to energy inefficiency. 

It's important to choose the right size because a system that's too large short cycles, which means that it runs for short periods more frequently. This drives up your energy bills and increases the wear on all the system's parts. Oversized systems don't remove as much humidity, either, a critical aspect to cooling in our region. 

An air conditioner that's too small won't be able to adequately cool your home during our hottest weather, but in most cases, it's better to select a system that's smaller rather than too large.

For more information about the load calculation, contact Tri-County Heating & Cooling. We've provided Bulter County and Greater Cincinnati expert heating and cooling services for more than 40 years. 

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