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A Closer Look at Variable-Capacity Central AC

What’s the ultimate central air conditioner, in terms of comfort, efficiency, operating sound levels, and more? We’ve discussed variable-capacity central air conditioners before, and in this blog we’re going to dive a little deeper into how these state-of-the-art central AC systems work, what makes them unique, and why you might consider one for your home.

Along the way, keep in mind that central heat pumps, which are also available as variable-capacity units, are virtually identical in operation and performance to central AC systems when it comes to cooling during the summer. The bonus with heat pumps is that they also operate in ‘reverse’ during the wintertime, serving as a heat source. In our Colorado climate, it’s becoming more and more popular to couple a central heat pump with a furnace in a dual fuel system (gas furnace and electric heat pump) when installing new central AC.

How Does Variable-Capacity Central AC Work?

Variable-capacity air conditioners automatically adjust their cooling output upward and downward, as needed, depending on the specific cooling needs of the home. This is very different than the conventional single-stage air conditioners that most of us tend to think of. Single-stage systems simply turn ‘on’ or ‘off,’ delivering the same full amount of cold air to the home regardless of whether it’s 75 or 95 degrees outside. When outdoor temperatures are more moderate, as opposed to baking hot, a single-stage system is often likely to produce short, inefficient, uncomfortable cooling cycles, with wide temperature swings between each ‘call’ for cooling.

Variable-capacity systems monitor indoor and outdoor temperatures in real time during operation, and automatically adjust cooling output up or down in increments as small as 1% of rated output. The Lennox product line that we continue to have great success with features the ability to modulate output downward to as low as just 35%, producing 65 different custom levels of cooling.

So when outdoor temperatures are warm but not scorching, a variable-capacity system operates at a much lower cooling output in order to best satisfy the comfort needs of the home – doing this at lower fan speeds and sound levels, and using even less electricity in the process. This design affords improved accuracy in tracking thermostat temperature settings, and also eliminates broad temperature swings between cooling cycles, along with other benefits.

The benefits of variable-capacity air conditioners include:

• Quietest operation
• Very high efficiency and lowest operating costs
• Most accurate at tracking and maintaining thermostat temperature settings
• Greatly reduces wide temperature swings between cooling cycles
• Provides the most uniform comfort around the entire home
• Helps reduce broad temperature differences (stratification) between the main floor and upper levels of a home, or rooms located far from the furnace
• Improved furnace filter performance
• Smart phone connectivity available on many models, along with diagnostic enhancements to assist with troubleshooting

How Efficient is Variable-Capacity Central AC?

Variable-capacity central AC systems are among the most efficient you can buy, and are available in a variety of models ranging from what’s considered high efficiency to the very top of the line. Depending on the model, efficiency ratings for these units range from approximately 18 SEER (Seasonal Energy Efficiency Ratio) to ultra-high 28 SEER.

Other Variable-Capacity Central AC Considerations

Compatibility With Your Existing Furnace

The advanced features and benefits provided by variable-capacity central AC systems normally requires that the air conditioner is matched with a furnace that has compatible features, specifically a variable-speed main blower. These days, many existing furnaces don’t have that type of fan, and sometimes it’s a deal-breaker when someone is told they also need a new heater in order to install one of these premium AC systems. It’s important to note, however, that during the heating season, variable-speed furnaces also bring a lot to the table in terms of benefits. Variable-speed furnaces are available in both the 80% and 90+% AFUE efficiency ranges.

Of note, variable-capacity central AC units that are compatible with conventional furnaces are starting to become available. Currently, their efficiency ratings are not thrilling our team, compared to matching with a variable-speed furnace, but these units are nonetheless worth learning more about.

Our process with our customers at Save Home Heat is always highly informative, low-pressure, and sensitive to budgetary concerns when discussing any type of cooling (or heating) system. We regularly explore a variety of cooling options when providing free install quotes. Fortunately for our team and our customers, our central AC and furnace partner, Lennox Industries, offers a broad line of high quality equipment to fill a wide range of homeowner needs.

The Two-Stage Option

For those homeowners who are attracted to the many benefits of variable-capacity cooling (and heating!), but for any number of good reasons don’t feel this is the right investment for you, keep in mind that two-stage central air conditioners and furnaces might be just what the doctored ordered. Two-stage systems represent a happy medium between pulling out all the stops for the ultimate comfort system featured in this blog, or settling for a more traditional solution whose comfort levels may leave a bit to be desired.

Please contact me to discuss cooling options for my home!