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Understanding Different Furnace Sizes for Your Home: 14.0, 17.5, 21, and 24.5 Inches

Furnace Sizes

Brian Schaeffer |

Size Matters in Home Furnace Selection Both the heating capacity (in BTUS) and the actual size of the furnace itself, usually referred to by cabinet width. Available cabinet widths are typically 14.0, 17.5, 21, and 24.5 inches based on applications in home sizes and ductwork configurations. To get a better idea of what each of these typical furnace sizes means to somebody like yourself, let us examine. 

14.0 Inches - A Size

Typically the smallest standard size, a 14.0-inch furnace is appropriate for smaller homes. Ideal for small to medium-sized homes with modest heating needs. Additionally, a 14.0-in cabinet can usually squeeze between standard wall studs, so it is ideal for retrofit installations or where space is at a premium. While it may not be the same smaller than you are a model can still do a good job of keeping heat moving in a smaller home. 

17.5 Inches- B Size 

The 17.5-inch furnace is a larger version of the same concept. It is typically used in medium size houses which have higher heating loads than smaller units can satisfy. The size also might be slightly better suited to larger ductwork in homes, given that it is capable of moving air more effectively through wider ducts. The 17.5 inch size sits in the sweet spot of compactness for most homes, while also offering the necessary heating firepower. 

21 Inches- C Size

For most residential installs, a 21-inch furnace is the standard size. Medium to large homes with major heating needs A larger cabinet means a larger blower and heat exchanger and a more efficient burning of gas to heat a wider area. If your home is large and has more square footage, or if you live in a cold climate and require significant heating capacity then the 21-inch furnace would be the best choice. 

24.5 Inches- D Size

24.5 inch is standard as far as all home heating metal goes So it's for bigger houses, particularly those with a considerable amount of square footage or that require more BTUs to remain comfortable. The large cabinet size requires a larger blower and heat exchanger capable of effectively managing the heating needs of a spacious home. This size also found in buildings with a lot of duct work. 

Considerations Beyond Size 

So, the size of one's furnace is very important but not the only thing to consider. There are many factors that will affect exactly which furnace is right for your home including the heating capacity, efficiency rating, type of furnace: single-stage, two-stage, or modulating), and compatibility with you existing ductwork and ventilation. 

In most cases, a professional HVAC technician should make it a point to perform Manual J calculations that will help establish the right heating needs and avoid spending more on large, unnecessary systems. After the furnace capacity is determined, a load calculation will determine what you need based on things like the climate where you live, how well insulated your home is, what type of windows you have, and other factors that help ensure that you get both the right size and the right furnace sizing for whatever requirements apply to your situation. 

In other words, understanding furnace dimensions and how they play into your heating requirements in the home is critical to providing ideal comfort and energy saving. When in doubt, contact that can help you to steer in the best direction for your same unique situation.