Types of Furnaces: What Buyers Need to Know

​Older furnaces are all single-phase, which means they always produce heat at full capacity while running.

If a home’s furnace is outdated and the energy bills are increasing, it may be time to invest in a new system. Homeowners must understand the different types of forced air furnaces, as there are several distinct types, each with its own advantages.

​Differences between furnaces

There are a few key distinctions between furnaces and how they work. The first distinction is the method through which the furnaces generate heat. Some generate heat in one step, referred to as a single-phase furnace, while others do so in two steps, referred to as a two-phase furnace.

The second significant distinction between furnaces is how their blowers work. The blower distributes generated heat throughout the home. The blowers on some furnaces run at full speed all the time. Others operate their blowers at different speeds, impacting comfort and efficiency while in use.

Single-phase versus two-phase furnaces

​Older furnaces are all single-phase, which means they always produce heat at full capacity while running. Single-phase furnaces come at a lower cost, making them appealing to those looking for an economical option. Two-phase furnaces are noted for being more efficient, with AFUE (annual fuel usage efficiency) values often exceeding 95 percent. On the other hand, single-phase units typically have AFUE levels in the 80s.

Because of how these two types of furnaces work, there is a significant efficiency gap between them. After going through the warm-up process and functioning for longer periods, furnaces are at their most efficient. As a result, an oversized furnace is always less efficient than one that is correctly sized. A single-phase furnace turns on, warms the house, and then turns off. During the coolest part of the day, a two-phase furnace turns on at full power to warm the home. It does not turn off after the home is warm; instead, it reduces the heat output to a low level, continues to run, and tries to keep heat levels within a degree or two of the thermostat’s settings. A two-phase furnace operates economically by operating continuously and cycling between high and low heat output levels to keep the home at appropriate temperatures.

Variable speed versus standard furnaces

​Some furnaces use constant power blowers. Others use a blower that accelerates and decelerates depending on how hot the home is. If the house only requires a minor boost in warmth, the blower can run at a lesser speed, saving energy and creating a more comfortable environment. Not only that but this type of blower has been proven to have a longer operating life and should be able to keep the home at a pleasant temperature for years longer than a standard single-speed blower. A variable-speed blower can precisely supply the proper quantity of heat and is frequently used in conjunction with a two-stage furnace to achieve maximum efficiency.

Single-stage furnaces are less efficient than two-stage furnaces, and furnaces with variable-speed blowers are even more efficient. These more modern and efficient furnaces are a little more expensive upfront. Still, they should make up for it with increased efficiency and a more comfortable environment throughout their lifetime, making them a worthy investment.

Just in Case Mechanical offers residential and commercial plumbing, sewer, water softener, electrical, lighting, and HVAC services Lancaster County. Call us today at (717)696-1511.