Not all heating, ventilation and cooling (HVAC) systems operate at a single speed. Some of them are capable of operating at multiple speeds. Known as variable-speed HVAC systems, they’ve become increasingly popular in recent years. They can heat and cool your home just like their single-speed counterparts. The only difference is that variable-speed HVAC systems offer multiple speeds.
Understanding Variable-Speed HVAC Systems
The term “variable-speed HVAC system” can be somewhat confusing because it can refer to different types of technologies. There are air conditioning systems with a variable-speed compressor, for instance, and there are air handling units (AHUs) and furnaces with a variable-speed blower. They both live up to their namesake by offering multiple speeds. Variable-speed compressors and variable-speed blowers, however, work in different ways.
How a Variable-Speed Compressor Works
With a variable-speed compressor, your air conditioning system’s compressor will automatically adjust its speed to achieve longer cycles. It won’t run at 100%. Rather, the compressor may run at just 25% to 50%. This lower speed setting means that your air conditioning system won’t cycle on and off frequently. It will continue to run while removing heat from your home’s interior.
There are the single-speed and two-speed compressors as well. Single-speed compressors are those that operate at a single speed, whereas two-speed compressors are those that operate at two speeds. Variable-speed compressors are distinguished by their ability to operate at many different speeds.
How a Variable-Speed Blower Works
Variable-speed blowers are found in ACUs and furnaces. All HVAC systems have a blower. In a standard air conditioning system and furnace setup, the blower will usually be installed in the furnace. In a heat pump HVAC system, on the other hand, the blower will be installed in an ACU.
Like with air conditioning systems, some blowers are capable of operating at multiple speeds. A variable-speed blower will respond to temperature changes inside of your home to conserve energy. If the temperature is approaching that for which you set the thermostat, it may operate a lower speed setting.
Most variable-speed blowers have an electronically commuted motor (ECM). The ECM receives data from your home’s HVAC system, which it uses to automatically adjust the speed of the blower. Whether you’re trying to cool or warm your home, the variable-speed blower will adjust itself. The end result is a more efficient HVAC system that conserves energy.
