Living in Cincinnati: Sizing Your New Air Conditioner
by Greg Leisgang on June 27, 2013
Posted in: Installation
Sizing your new air conditioner is an important part of the system upgrade process, second only to selecting a reputable and experienced contractor to perform the sizing calculations accurately and to install the unit. There’s a lot at stake with a system upgrade — home comfort, energy bills and operating costs — and the choices and calculations you and your contractor make are choices you’ll live with for many years.
Manual J: Residential load calculation
The cooling capacity of an air conditioner is defined by its size. To determine the correct size of air conditioner to install, you must determine the cooling load placed on it by your home.
Manual J is the HVAC industry's standard method for calculating a home's cooling/heating load, taking into account dozens of variables. In today’s tightly sealed homes, accuracy and contractor expertise are paramount. An accurate load calculation boils down to seven factors:
- Home size, layout and orientation to the sun
- Local climate, including average, minimum and maximum temperatures and humidity
- Insulation qualities
- Air exchange rate
- Window sizes, locations and types
- Number and ages of occupants, as well as their energy usage habits and comfort preferences
- Heat gain as a result of lighting and appliance efficiency
Manual D: Residential duct system
Once air conditioner size has been determined, your contractor will evaluate duct efficiency and size for handling the new system. High-efficiency air conditioners have redesigned coils which are considerably larger than older models and may require duct modifications to accommodate them.
If you've decided to retrofit your ducts for optimal efficiency and comfort, ACCA’s Manual D is used to design the new duct system. Some of the attributes of good duct design include:
- Conditioned spaces used for duct runs
- Joints sealed with screws, mastic and metal tape
- Return grille, transfer grille or jumper duct installed for each supply outlet
- Balanced air supply and air return through the forced air system and living spaces
If you have any questions about sizing your new air conditioner or the process involved, the professionals at JonLe Heating & Cooling will work closely with you to ensure your 100 percent satisfaction. We’ve provided HVAC services for greater Cincinnati area homeowners since 1959.
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