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How We Size Central Air Conditioners

Published on: July 9, 2013

You rely on your home’s air conditioner to keep you cool even when temperatures are sizzling outside. If your air conditioner simply isn’t cooling your home down like it used to, it might be time to shop for a new AC unit. As you shop for a new air conditioner, remember to work with a professional contractor. Your contractor will help you choose an AC system that is correctly sized for your home or space. Remember that only an experienced, licensed contractor can complete cooling load calculations and system sizing according to Air Conditioning Contractors of America (ACCA) criteria.

Should You Rely on A Professional to Size Your Air Conditioner?

Many homeowners know that size matters when it comes to air conditioning units, but they’re not sure if they really need professional help to choose a unit of the right size. While it might seem easy to find a unit suited to your home’s needs, it’s important to remember that your contractor will thoroughly inspect your home before making sizing recommendations. Remember that choosing a system of the correct size is one of the best ways to cut home energy usage and lower electricity bills.

How is The Capacity of Central Air Conditioners Measured?

The capacity of all central air conditioners is measured in terms of British Thermal Units (BTUs). Basic determinations about how many BTUs are needed to cool a space efficiently are made by looking at the total square footage of the area to be cooled. However, the overall design of the system and the structure of your home will also affect the BTUs needed to keep you comfortably cool. Remember that you may need to compare several AC systems of the same size to find the one that is best for your needs.

How We Size Central Air Conditioners for Your Space

All of the contractors we work with at Air Conditioning South East use ACCA-approved methods to size central air conditioning systems. In fact, many states require contractors to complete sizing calculations before installing new HVAC systems. As you work with your contractor, you are likely to hear about two different methods for calculating cooling loads. If you are having a system installed in a new home, both methods will be used.

Manual J and Manual D Calculations

Manual J calculations take your home’s overall size, design, structure and energy efficiency into consideration. Your contractor will look at factors such as how much heat your home gains and loses over the course of an average day in order to make sizing decisions. Manual D calculations are completed only when a new ductwork system is being installed. Your contractor will use both Manual J and Manual D calculations when designing a new duct system.

Working with Your Local HVAC Sizing Professionals

At Air Conditioning South East, we know that finding solid answers to your HVAC questions can be tough. Thankfully, you can use our free, online tools to find a qualified contractor in your area. We are happy to connect residential and commercial customers in Mississippi, South Carolina, Georgia, Florida and Alabama with professionals who can assist with AC system sizing.