There are a lot of choices when it comes to replacing your home’s comfort system. Single stage, two stage and variable speed compressors are all available. What’s the difference? And, why Choose a Variable Speed Comfort System?
Representing the latest in residential air conditioning technology, a variable speed compressor is a gigantic leap forward for achieving optimal efficiency and comfort indoors. If you’re wondering about the primary difference between variable speed, two stage, and “traditional,” single stage comfort systems, here’s the simple answer: Variable speed is the best.
Most homes in Alabama with central air conditioning use a single stage compressor. These compressors were the standard for decades, and they continue to represent the majority of AC units we service in the Childersburg area.
A single stage compressor turns on when indoor temperatures exceed the temperature setting on your thermostat. For example, if you set the thermostat to 75 degrees, the air conditioner will run anytime indoor temperatures hit 76 degrees. After the AC cools the house back to 75 degrees, it will turn off again.
Single stage compressors always operate at 100% capacity. They turn themselves on and off continuously throughout the day.
Variable speed compressors work differently. In order to maintain an indoor temperature that matches the setting on your thermostat, they operate continuously at less than 100% capacity – often as low as 25% or 30% capacity. As a result, they run for much longer cycles than single stage AC units.
In summertime, they might run for all or most of the day!
Here’s a way to get your understand the difference:
•Single stage compressors blast your home with cold air and turn themselves off when when the desired temperature is reached.
•Variable speed compressors blow a smooth, steady stream of cold air into your home to maintain the desired indoor temperature, rarely turning themselves off.
A two stage or dual stage compressor sits somewhere between single stage and variable speed systems in terms of how it functions. While it doesn’t operate at a wide range of capacities like a variable speed unit, it does vary its output somewhat.
A single stage AC offers one level: high. A two stage AC offers two levels: high and low.
It runs at full capacity when you need it to and at a lower level when you don’t. Two stage units don’t run as continuously as a variable speed AC, but they do cycle on and off less frequently than single stage systems.
At this point, you’re probably thinking, Why would I want an air conditioner that runs longer and cools
my home more slowly?”
One reason is, a variable speed compressor’s longer run times dehumidify your home more effectively than the relatively brief cycles of a single stage unit. One of the biggest problems with single stage compressors is that they’re not running continuously. Relative humidity increases whenever the AC isn’t on, making you feel hotter and more uncomfortable. This is especially noticeable when an air conditioner is too big for your home, as they often are.
Most people deal with this problem by lowering the temperature on their thermostat, which brings us to the other benefit of variable speed compressors: cost.
A single stage compressor blasts your home with cold air before it turns itself off. Then it turns on again when the indoor temperature increases. Most of your air conditioner’s electricity draw occurs when it turns on, not while it’s running. In the summer, a single stage compressor turns on and off a lot, a process known as “short cycling.”
Since single stage compressors tend to short cycle, they usually draw a lot more electricity than a variable speed unit that turns on and stays on for hours. As a result, the single stage AC is much more expensive to operate!
When it comes to comfort and efficiency:
• Single stage air conditioners don’t dehumidify indoor air very well, forcing you to lower the temperature setting on your thermostat. They also turn on and off a lot, which increases your energy bill.
• Two stage compressors don’t turn on and off nearly as much. They’re more efficient than single stage units, but not as efficient as variable speed compressors.
• Variable speed air conditioners run continuously, effectively dehumidifying the air inside your home. As a result, you feel comfortable at higher temperatures and don’t have to set your thermostat to a lower temperature. And since they don’t turn on as often, variable speed AC units lower your utility costs.
More effective heating and cooling and greater efficiency aren’t the only benefits of a variable speed compressor.
If you’re concerned about indoor air quality, opting for a two stage or variable speed unit can help purify the air circulating around your home, resulting in healthier conditions for you and your family. Since they dehumidify indoor air more effectively than a single stage unit, a more efficient system helps you:
•Eliminate mold growth in bathrooms and kitchens
•Prevent the proliferation of dust mites
•Create conditions that are inhospitable to insect intruders
And since variable speed units run more frequently, they also filter your indoor air more effectively. More air is cycled through your air ducts and your air filters resulting in a lower volume of air contaminants.
They’re also quieter than single stage compressors. If you’re used to warm or cool air exploding into your home like a sudden gust of wind, you’ll probably be surprised by the variable speed unit’s more subdued, consistent air flow.
Understanding the differences among single stage, two stage, and variable speed compressors might make you want to explore the idea of upgrading your existing unit. Before doing so, here are two things to keep in mind:
Variable speed compressors cost more because they provide an overall better HVAC system for your home. When weighing your options for new equipment, you’ll have to consider whether upgrading to a variable speed unit aligns with your budget.
There might be other ways to lower humidity, improve indoor air quality, and improve comfort without purchasing a two stage or variable speed compressor. Here’s what we recommend to our clients:
• If it’s time to upgrade an aging HVAC system, variable speed is the way to go. Already planning to replace an existing air conditioner? Assuming your budget accommodates a variable speed unit, you should definitely get one! You’ll feel more comfortable throughout the summer months, and your indoor air will be whole lot cleaner. At the very least, consider a two stage compressor for improved comfort and efficiency.
• If your single stage HVAC system isn’t old enough to justify replacement, consider a whole house dehumidifier. By installing dehumidification equipment inside an existing single stage system, you can enjoy some of the benefits of a variable speed compressor without replacing any equipment. The dehumidifier will keep your relative humidity at a comfortable level, improving indoor air quality and enabling greater comfort at higher temperatures.
• If it’s time to replace your AC and you love your single stage unit, stick with what you know. Replacing an old 8 SEER single stage AC with a new 14 SEER single stage AC still results in a more efficient system. If your relative humidity is consistently below 55 percent and you don’t suffer from poor indoor air quality, you might not need a variable speed unit.
What’s great is that there are so many options these days for optimizing indoor comfort and HVAC efficiency. A decade or so ago, AC choices were limited to several extremely similar single stage compressors, all of which provided lousy efficiency by modern standards.
If you have questions about your home’s HVAC system, or are considering updating your system, give Sleeping Giant Heating and Cooling a call at 256-378-6556. Or, email us at info@sleepinggiantair.com.
Sleeping Giant Heating and Cooling is a fully licensed and insured HVAC contractor located in Childersburg, AL. We’ve been serving the HVAC needs of the Childersburg area since 1963.
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