August 28th, 2020

Hey everybody, Cosmo here! It seems like only yesterday that The Boss was warning us about the negative effects of an oversized AC system. Now that cooling season is on the way out and heating season will soon be upon us, it’s time to talk about the hazards of an oversized furnace. 
The most obvious effect of a furnace that’s too small is a cold house, but here are six things that can result from an oversized furnace, some of which may surprise you:

Wasted Energy

Oversizing is one of the most common reasons a furnace will short-cycle. This happens because after the furnace delivers heat to the home and has raised the temperature (as instructed by the thermostat), the thermostat signals the furnace to turn off again. Furnaces use the most energy when they’re starting up, so by starting multiple cycles, the furnace consumes more energy than one that tuns on and runs for a long stretch of time. 

A Shortened Furnace Lifespan

As a furnace repeatedly heats up and cools down due to short-cycling, it puts a lot of stress on the furnace’s components, especially the heat exchanger, igniter, and gas control valve. As these parts are used and overused, it increases the likelihood of mechanical failure and the need for a repair or a total replacement. 

A Pricier Installation

In addition to paying more each year on your heating bills, an oversized furnace will cost you more upfront. Larger furnaces require more burners, larger fans, and more sheet metal in the exterior cabinet and heat exchanger, all of which drive up the product’s price.

More Noise While the Furnace is Running 

It’s a general rule that large machines tend to make more noise than small ones, and furnaces are no exception. Larger furnaces are designed to move more air and will make more noise in the process. The problem will be compounded if your ductwork is undersized (as is sometimes the case when a furnace is oversized). This combination will result in increases in velocity and turbulence, creating more noise. 

Unreliable Heating

Being oversized causes a furnace to bring too much heat to some areas and not enough to others, because it won’t have enough time to heat evenly before shutting down again. An oversized furnace can cause further discomfort with excessive airflow from registers, caused by excessively large and powerful blowers. 

A Threat to Your Well-Being

So far, we’ve discussed how oversized furnaces can cost you money and comfort – but they can also affect your health. A properly sized furnace will use its heat to dry out acidic condensate (water mixed with combustion by-products created while a furnace generates heat). If a furnace is oversized and shuts down before it can do this, it will cause the substance to accumulate throughout the furnace. This is known as “wet time” or “condensate dwell,” and can lead to corrosion and even discharges of carbon monoxide, a hazard you definitely want to avoid.

Sizing Your Furnace

Before installing a furnace, a conscientious contractor will perform a Manual J heating load calculation to assess your home’s unique needs. Everything from geographical location and which way your house faces to air-tightness and insulation is taken into account to facilitate high-efficiency heating.  At SG Heating & Air Conditioning LLC, we have extensive experience installing furnaces in Princeton, NJ and throughout our service area, including Manual J heating load calculations. For heating solutions including furnaces, boilers and heat pump repairs in Mercer County, NJ, call us today at 609-448-1273!

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