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Thinking About Buying An Oversized Furnace? Think Again!

There aren't many situations where more isn't better. Everyone would like more money, time, and friends, but your home's HVAC system may be the exception that proves the rule. Taking the "more is better" approach with your new furnace can potentially severely affect your long-term operating costs and comfort.

But, what if you want to be sure that your system can deal with the coldest weather your region can throw? Doesn't it make sense to buy a system with a little more power than you need to ensure it can get you through those cold nights? Unfortunately, sizing up rarely provides the benefits you might expect, even when it seems justified.

How Furnace Sizing Works

There are two headline specifications for any modern gas furnace: capacity and efficiency, measured in BTUs (British thermal units) and AFUE (annual fuel utilization efficiency). While efficiency affects the cost of running your furnace, it's not particularly important for sizing. On the other hand, BTUs directly affect your furnace's ability to heat your home.

A BTU is a somewhat esoteric unit for measuring energy. The details of how a BTU is defined are unimportant, but a higher BTU rating generally means a higher capacity and greater ability to heat a space. The BTUs required to heat your house will depend on your home's size, climate, insulation, and other factors.

HVAC contractors recommend a furnace capacity based on a load calculation that considers these measurements. Sizing your furnace as closely as possible to your home's heating load will ensure that it provides the best possible efficiency, comfort, and reliability.

Why Oversizing Doesn't Work

Your furnace operates in cycles, turning on and off throughout the day. These cycles typically last for longer on very cold days and shorter on warmer days. Running for too long at once can stress system components, but very short cycles can be equally problematic. A short cycling system also cannot provide adequate air changes, reducing indoor air quality.

A system correctly sized for your home's heating load will typically run for long enough to maintain comfortable, even temperatures throughout your home. While running, the filter helps clean the air moving through the return vents, maintaining your indoor air quality. Even during extreme temperatures, a well-designed system will usually cycle at a reasonable rate.

Unfortunately, an oversized system throws this careful balance out of alignment. Your furnace will likely run only for short periods, causing your home to shift between too hot and too cold rapidly. Likewise, these short cycles won't last long, preventing the filter from doing its job. Ultimately, a correctly-sized furnace will always provide the best balance of comfort, efficiency, and reliability.

Contact a company like Master Mechanical, Inc. to learn more.