When it comes to HVAC systems, not all work in the same way. At a categoric level, standard HVAC systems operate at a single speed or stage whereas high-efficiency systems operate at varying speeds or stages, known as variable-speed HVAC systems. This guide will explore how standard systems work, what variable speed means, and how variable-speed systems help improve your home’s indoor comfort.

Understanding Standard Systems

Standard HVAC systems run on a single speed. This means the circulating fan, AC compressor and furnace burners are either on or off. Whenever they run a heating or cooling cycle, they run on high, producing or transferring the maximum amount of heat they can. It also means the fan runs on high for the entire heating or cooling cycle.

The cycle works by bringing your space to the temperature set on the thermostat and then shutting off. When the room temperature gets to the activation temperature again, the system starts back up. From a comfort perspective, this means that your home continually goes through temperature swings, albeit small ones in modern systems.

What Is a Variable-speed HVAC System?

As opposed to a single-speed system, variable-speed systems can adjust their capacity to meet the demand. It also means they run constantly rather than 10 to 20-minute cycles. This allows the system to maintain your home’s temperature rather than raising or lowering it repeatedly. Variable-speed systems include a central blower motor, an air conditioner or heat pump, and likely a gas furnace. Remember that your system won’t have a variable-speed compressor or burner without a variable-speed fan. Both are necessary for proper function.

Central Blower Motor

The central blower motor is responsible for drawing air from around your house and then circulating conditioned air throughout your home. A variable-speed fan can run on a wide range of speeds to meet the demand throughout the day. The lower setting on the central blower cycles less air at a time, but more air overall.

Air Conditioners and Heat Pumps

For air conditioners and heat pumps, the compressor will vary to adjust the capacity as it runs. The different speeds or levels a compressor runs at are known as stages. Variable-stage compressors can have up to about 700 different settings starting at about 25% of the heat transfer capacity. The lower the compressor setting is the less energy it uses and the less strain and wear it experiences. A lower heat transfer capacity means that the air coming from your supply vents won’t feel as cool during cooling mode or as warm during heating mode, so remember there isn’t something wrong with your system when you notice it.

Furnaces

How much heat a furnace produces is what adjusts in a variable-speed system. To do this, the unit must be equipped with a modulating burner. It controls heat production by controlling the amount of gas burning during a heating cycle. Think of a propane gas grill and how you can make it hotter by allowing more gas to flow and increasing the size of the flame. A modulating furnace burner does the same thing. By modulating the burner flame to only what you need, you can increase your system’s efficiency.

Improved Indoor Comfort

Now that you understand what a variable-speed HVAC system is, let’s explore how it improves indoor comfort. This comes in the form of temperature control, noise, air quality, humidity control and ease of operation.

Better Temperature Control

Most property owners appreciate the more accurate temperature control afforded by variable-speed systems. Rather than constantly feeling like you’re too cool or too warm, you can find a setting that’s comfortable throughout your home with your variable-speed system.

Part of this is not just the temperature at your thermostat, but also throughout your home. Because these systems tend to run nearly constantly, which means circulating conditioned air constantly, they can better reach all areas of your home. To gain even more control, you can pair a variable-speed system with HVAC zoning to ensure the conditioned air is always directed to the areas of your home that need it right then.

Quieter Operation

One of the challenges of running an HVAC system is the noise produced by the circulating fan. As you can experience with a desktop or ceiling fan, the faster it spins and the more noise it produces. Variable-speed systems operate at a lower capacity about 80% of the time in many cases. What this means for your home is that it may not be as noticeable 80% of the time, allowing you to enjoy conversation or entertainment without the intrusive noise.

Improved Indoor Air Quality

One of the secondary functions of your HVAC system is improving your home’s air quality by removing airborne contaminants with the air filter. These contaminants are known for creating dust and causing health issues in the form of allergies, asthma triggers and respiratory irritation.

With the increased cycle time of variable-speed HVAC systems, air constantly moves through the filter, allowing it to remove more contaminants. With this benefit, you’ll want to keep a closer eye on your system to prevent it from running with a clogged filter.

Better Humidity Control

Humidity can make your home feel muggy and uncomfortable, especially over the summer. Your HVAC system, especially your air conditioner, helps draw humidity out of the air. A variable-speed HVAC system still gets the evaporator coil cold enough to condense moisture from the air. Like air quality, it can pull more moisture from the air because of the longer cooling cycle. Further, it distributes dryer air more evenly around your home with longer cycles. The better your system helps control your home’s humidity, the more comfortable it’ll feel, even at slightly higher temperatures.

Easier Operation

Finally, a variable-speed HVAC system is generally easier to operate at maximum efficiency. A standard single-speed HVAC system needs thermostat programs that adjust the set temperature while people are away from the house to achieve maximum operational efficiency. Variable-speed systems don’t need the programs because they aren’t raising and lowering the temperature but working to maintain the temperature. This is the same reason why the Department of Energy does not recommend thermostat programs when using a heat pump. Keep in mind that you need to have a thermostat that’s compatible with variable-speed systems.

For more than 20 years, people around Metuchen have turned to First Choice Plumbing, Heating, Air Conditioning & Electrical to keep their homes comfortable. Our team provides heating and air conditioning installation, maintenance and repair together with plumbing services like plumbing and sewer repair, water heater installation and repair, sump pump service, toilet and other fixture installation and repair along with indoor air quality solutions.

Call to schedule a consultation with one of our Nate-certified HVAC technicians to explore whether a variable-speed HVAC system is right for your home.