Bigger Isn’t Always Better: a larger A/C unit or furnace isn’t always the answer

Article written by Zach Motsinger, a Member Service Technician and Energy Advisor at Orange County REMC. This article was published in the July 2019 issue of Indiana Connection magazine.

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Bigger must be better! This is a common misconception of many home owners during the heating and air equipment buying process. Although it may sound attractive to size your system to its largest capacity, from an energy efficiency standpoint, it is never a good idea to oversize your furnace or air conditioning unit.

Have you ever noticed the difference in warmth from the air when humidity is high versus low? If humidity is removed from the air, you feel cooler. This benefits your air conditioning unit, but not your home’s heating ability. When a furnace is oversized, the air will become excessively dry. Adversely, when an air conditioner is oversized, not enough humidity is removed. In either case, the homeowner will feel uncomfortable and stress the need to increase his or her thermostat to achieve a satisfying comfort level.

Heating, ventilation and air conditioning (HVAC) systems are not designed to continually be adjusted and could even short cycle if the homeowner is not careful. This could result in excessive wear and tear on motors and starting components, which could ultimately cost you more in the long run. The life expectancy of a system will decrease and the efficiency and operating cost will increase. For an easy to understand example, this cyclical process is similar to fuel efficiency in an automobile when driving in the city versus driving down the interstate.

It is important to remember that even though oversized systems will satisfy the temperature setting on a thermostat, an oversized air conditioner that begins to short cycle will not be able to remove humidity from the home.

Over time, the moisture being left behind will start to become noticeable. In some severe cases, moisture can be seen dripping from walls and the presence of mildew can be detected. This may become a big problem as mold could start to grow in the walls and on surfaces. This problem will leave many homeowners confused as they look at the thermostat, which has reached the desired temperature, but they’re still not comfortable.

The only way that an air conditioner can remove humidity from a space is by longer run times. When an air conditioner runs longer, it has more time for the indoor coil, or evaporator, to grab moisture out of the air and drain it to the outside.

Proper sizing of your home’s comfort system is important. When it comes time to install a new heating and air system, whether it’s replacing an existing system or new construction, request that your contractor run a heating and cooling load calculation. With the advances in technology, load calculations can be computed easily with software.

One more thing a homeowner should pay attention to is the equipment itself. Always check that the equipment is certified with the Air Conditioning, Heating, and Refrigeration Institute (AHRI). AHRI ensures that manufacturers are accurately listing ratings of their products and sets standards for consumers to compare equipment. When it comes time to purchase a furnace or air conditioner, remember that the proper size is the key to comfort!

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