Sizing Your Air Conditioner: The ABC’s Of Manual J

Size is a critical factor in choosing an air conditioner. Comfort, cost and efficiency all rely on a properly sized air conditioning system. An accurate way for an HVAC professional to determine this is through Manual J, a protocol developed by engineers to calculate the heating and cooling loads of a building.

Three important pieces of information about your home’s heating and cooling system are determined using Manual J. These are:

• Heating load: Amount of energy needed to heat up your home on the night of the coldest day of the year.
• Sensible cooling load: Amount of energy needed to remove heat that you can feel with your body and measure with a thermometer during daytime on the warmest day of the year.
• Latent cooling load: Amount of energy needed to remove humidity.

According to the Manual J calculation, your air conditioner should be able to provide both the sensible and latent cooling loads of your home, and should only be up to 15 percent bigger than your actual cooling needs.

There are two types of Manual J load calculations: block load calculation and room-by-room calculation.

• Block load calculation: It determines the heating and cooling loads for the entire home, regardless of the individual energy needs in each room.
• Room-by-room load calculation: It provides separate calculations for every room, helping you decide whether to install separate thermostats for each room. It also determines how much air is needed in every room, a vital factor in properly sizing ductwork to deliver the right amounts of air to the different areas of your home.

It is in your best interest as a homeowner to demand that your contractor perform a Manual J calculation before choosing and installing a new air conditioning system.

For help with all your home-comfort issues, contact the experts at Sobieski Services.

Sobieski serves Wilmington, Delaware and the surrounding areas. Visit our website to see our special offers and get started today!