A variable speed furnace is a heating appliance with a blower motor in the gas furnace that facilitates air movement from the ductwork through room vents into the indoor spaces.
It contains an electronically commutated motor(ECM) that allows the furnace to operate at a high-efficiency level.
This speed blower works at a range of speeds to control the amount of airflow directed throughout your home. When a thermostat signals the system to produce heat, the gas valves located on your gas furnace open up, and the burners ignite. This heat warms the air pulled in from inside your home. For the warm air to get pushed out of the furnace, the variable speed blower sets in and distributes the heat through room vents into your rooms. When the heating demand is low, it works at a low speed, and when the demand is high, it works at high speed to keep up with the needs. The variable speed furnace monitors data from the HVAC system and makes blower motor speed adjustments. This system takes into account dirty furnace filters and blocked vents and adjusts the fan speed to compensate for the fault. Some variable speed furnaces maintain the indoor temperature because the gas furnace doesn’t wait for the room temperature to go low before it restarts. The speed furnace operates at low speed to keep the air moving throughout your home even when no heat is required. This helps keep the air moving through the furnace filters where the air gets filtered, allowing contaminants to be trapped in the air filter. It has better humidity control compared to conventional furnaces. While single-speed furnaces operate fully OFF or fully ON, a variable-speed gas furnace adjusts its output to maximize efficiency and provide comfort.