Sizing an A/C: It’s All About Manual J

Sizing an A/C: It's All About Manual JIf you are shopping around for a new A/C to replace the old system in your Rochester home, you will find more energy-efficient A/Cs and add-ons on the market than ever before. Be mindful that making the most of your A/C investment does not mean over-paying for an oversized A/C. Work closely with a reputable contractor who understands that sizing an A/C results in your investment dollars being well spent, and a nice energy-savings return.

Sizing an A/C

A correctly sized A/C meets the heat gain of the home without being too big or too small for the job. Calculating a home’s heat gain, and subsequently sizing the A/C, is a complex procedure involving dozens of measurements and assessments for home design, insulation attributes and occupant information, such as energy usage habits, number, ages and schedules.

The Air Conditioning Contractors of America (ACCA) developed guidelines for sizing an A/C (Manual S), and measuring the cooling load of a home (Manual J). These publications are standard equipment for responsible contractors in the HVAC industry for correctly sizing an A/C.

Right-Sizing, Right Results

An A/C should cycle for no less than 15 minutes for optimal results of home cooling and dehumidification. An over-sized A/C forces airflow through the home too quickly in large volume. This creates noise disturbances from the air ducts, uncomfortable blasts of air and short cycling. The over-sized A/C never reaches peak energy efficiency for which it was designed, and you suffer with high cooling bills and discomforts.

On the other hand, an A/C that is sized by Manuals J and S is selected and installed to meet the actual cooling load of the home. Moreover, if you decide to install add-ons, such as a zoning system or whole-home air purification system, the computations reached using Manuals J and S become more valuable, and may result in a smaller A/C (and subsequent lower sticker price).

Sizing an A/C requires the expertise of an experienced HVAC contractor. For more information, contact us at Aladdin Heating & Cooling for help sizing and selecting the right A/C for your Southeast Michigan home.

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

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