Manual J: Why The Contractor Who Sizes Your Air Conditioner Should Know It Inside Out | Acosta Heating, Cooling & Electrical
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Manual J: Why the Contractor Who Sizes Your Air Conditioner Should Know It Inside Out

Posted on: June 14, 2012

The purchase of a new or replacement air conditioner for your home is not simply a matter of choosing a cooling unit and having it installed. Among the more important of the additional considerations is determining what size cooling system you need. The amount of cooling required to keep your home at desired levels is your home’s “load,” and each home has a different one. The air conditioner you choose must be correctly sized—big enough to meet the load, but no so big that it overcools and wastes energy.

If you are in the market for a new air conditioner, you should know your home’s cooling load. Ask your local trusted HVAC contractor to conduct a load calculation on your home using the industry-standard Manual J, “Residential Load Calculation.” This manual, published by the Air Conditioning Contractors of America (ACCA), contains all of the standards, procedures and technical details required to perform heating and cooling load calculations.

A Manual J cooling load calculation will give your contractor two important pieces of information needed to select and size your new air conditioner:

1. Sensible cooling load:

Proper cooling requires effective removal of sensible heat. Sensible heat is the amount of heat that can be felt, or sensed, and measured with a thermometer. The sensible cooling load is the amount of sensible heat that your air conditioner should be able to remove during very hot days. Manufacturers rate their units at 95 degree outdoor the design criteria for your city could be higher which will require additional calculations

2. Latent cooling load:

Latent cooling load refers to how much moisture the cooling system can remove during hot and humid summer days. Latent cooling load determines the amount of energy needed for indoor dehumidification during these hot, muggy conditions.

HVAC equipment recommendations should be based on expert interpretation of sensible and latent cooling load data. The system you buy should be no more than 15 percent oversized based on these load calculations.

Acosta Heating, Cooling & Electrical has provided professional heating and air conditioning services to customers in Charlotte and surrounding areas for four decades. Contact us today for more information on heating and cooling load calculations for your home and why Manual J is the industry’s standard source for these calculations.

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