What is a Two-Stage Furnace?

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If you’re installing a new furnace, either for new construction or as a replacement, the contractor or salesperson will probably offer you the choice of a one-stage or a two-stage system. We generally recommend two-stage furnaces, for a number of reasons. Let’s explore why.

Related read: Is your furnace ready for winter?

In a traditional one-stage or single-stage furnace, the valve that controls the amount of fuel that enters the burner has only two positions: open and closed. When the valve is open, fuel feeds into the burner at only one rate of flow. The heat is either on full blast or it’s not on at all. The home’s comfort is regulated by the thermostat turning the furnace on when the temperature gets too low, and off again when it reaches the set level.

In a two-stage furnace, the fuel valve has three positions: fully open, partially open, and closed. This allows your furnace to be much more efficient, because it’s rare that your home is so cold that it needs the furnace to be running full-blast. The temperature inside a home changes gradually, and it’s more efficient to run the heat at a lower level to maintain a comfortable temperature than to wait until the home gets really cold and then heat it all up again.

The size of your furnace is based on the worst possible winter temperature in your area. For example, in Northern Indiana and Southwest Michigan, the worst possible day would be about -20 degrees. Therefore, for the majority of the season, a furnace only needs stage one.

A two-stage furnace has a 65 percent setting (stage 1) and a 100 percent setting (stage 2). It’s like a power setting on a microwave. You don’t want to defrost a roast by cooking the outside at 100 percent. A one-stage furnace often overshoots the desired temperature, whereas a two-stage furnace is able to push a lower amount of heat over a longer period of time. Don’t worry about comfort, though: when the house is extra cold, such as in the morning, the furnace bypasses the first stage and warms the house quickly.

In our market, 88 percent of the time your furnace is running at the first stage. In other words, only 12 percent of the time does your furnace run at full capacity. This is your opportunity to save money – as much as 25 percent of your gas bill.

Home Comfort Experts has an algorithm to show you how much money a two-stage furnace can save your specific household. Call us for more information: 574-255-4600.

The benefits of a two-stage furnace are not limited to saving money, however. They also result in a more comfortable home. With a one-stage furnace, all the rooms are at the mercy of the room with the thermostat, and they might cool down and heat up faster or slower. You end up with a home with cold spots, in which some rooms are never as comfortable as others. In contrast, with a two-stage furnace, in which the heat remains on at a low level for a longer time, all the rooms have a chance to achieve and maintain nearly equal temperatures.

Another benefit of two-stage furnaces is that they improve the air quality in the home. Because they tend to run longer and more frequently, they circulate the air in your ducts more frequently and, as a result, increase the filtration of the air.

Related read: Knowing when to repair or replace your furnace

Sold on the benefits of two-stage furnaces and want to know how to pick the best one for your home? In Sorthern Indiana and Southwest Michigan, contact Home Comfort Experts for a free in-home replacement estimate.

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