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Serving The Greater Fresno Area Since 1970

Serving The Greater Fresno Area Since 1970


Donald P. Dick Air Conditioning Blog

An Oversized Furnace Causes 2 Major Problems

An Oversized Furnace Causes 2 Major ProblemsTo ensure comfort and optimal efficiency, your home’s furnace must be sized accurately just like the air conditioner. Instead of using a rule of thumb to estimate the size, an HVAC contractor should perform a load calculation and consider key factors such as the home’s square footage, orientation, insulation level, windows and ductwork system.

You’ll experience two major problems if you have an oversized furnace installed in the home:

Inefficient Operation

When a furnace first cycles on, it’s not running at maximum efficiency. It won’t hit peak efficiency until the warm air it’s producing reaches a steady temperature. When a furnace is too large for a home, it reaches the thermostat’s target temperature while it’s still in this inefficient warm-up phase. This results in:

  • Short cycling. Once the temperature setting is satisfied, the furnace shuts down until the temperature drops again, and then the cycle repeats. If your home isn’t well sealed and insulated, the heat that’s produced will dissipate too quickly, so the furnace has to cycle on more often to maintain the thermostat setting.
  • Decreased comfort. Inefficient operation makes it more difficult to maintain comfort. Some areas of the home may be too warm, while others remain too chilly. You may find yourself adjusting the thermostat repeatedly in an attempt to keep the indoor temperature consistent.

Higher Costs

The inefficient operation of an oversized furnace can end up costing you more money in two ways:

  • Bigger energy bills. Because it’s operating in “warm-up” mode most of the time, the furnace consumes more energy than necessary. You’ll pay higher heating bills than you would with a properly-sized unit.
  • Premature equipment failure. Oversizing not only impacts your annual energy budget, it can also end up causing a premature failure that requires an expensive equipment replacement. With frequent on-off cycling, a furnace heat exchanger wears out years before its time due to the metal fatigue caused by repeated heating and cooling. The blower motor also will wear out sooner.

If you’re experiencing the problems associated with having an oversized furnace in your Fresno area home and need expert advice, contact us at Donald P. Dick Air Conditioning today.

Our goal is to help educate our customers in the greater Fresno, California area about energy and home comfort issues (specific to HVAC systems). For more information about oversized furnaces and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “Jaimie-Duplass/Shutterstock”


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