The blower (fan) motor in your furnace is responsible for pushing hot or cold air through your home. It is part of the furnace, but it is used for both heating and air conditioning functions.
ECM and PSC – What’s with all of the acronyms? These are easy ones really, ECM motors are mandatory in all new furnace based on government regulations, and this is good! Old furnaces used incredibly inefficient PSC motors. The new ECM motors are simply more efficient, more effective, and more intelligent. This all leads to a drop in your electricity bills. At the end of the day, you don’t need to worry about picking one or the other, since any new furnace will now have an ECM drive motor.
Multi-Speed Furnace– When referring to blower motors in a furnace this just means there are a number of speeds that a technician can select on your motor. Ideally, this will be based on the pressures and temperatures measured in your home during the installation process, not guess work. Once set, the furnace will always use the speeds that are selected. This is how blower motors have worked for decades, and is no different with the new ECM motors. This is very common, extremely efficient, and very comfortable when properly set up by a qualified installer.
Variable-Speed Furnace – All this means is that the blower motor can adjust the fan / air speed in your home on a variable scale, based on demand for hot or cold air. The idea (just like with stages in the above section) is to create a greater level of comfort. Just like with modulating gas valves, we don’t think the cost vs. the benefit is there with this option. These furnaces typically cost quite a bit more to install, and the benefit isn’t really noticeable. It’s more or less marketing hype, and a way to make more money if you work on commission. A properly adjusted multi-speed furnace will accomplish a phenomenal comfort level with great reliability.