Customer Reviews

What Are Furnace Stages?

The are several different types of furnace stages to choose from.  We explain what the differences are between a single, dual, and modulating furnace. Single Stage Furnaces Single stage furnaces have just one stage of heat output: high. A single stage furnace will output 100% at all times, regardless of the temperature outside or inside the home. Imaging always driving your car at highway speeds, regardless of the recommended speed limit or road conditions. That's how a single stage furnace operates: the gas valve is either on or off. Because you will size your furnace to some of the coldest days of the year, most of the time your furnace will be oversized. An oversized furnace can result in short cycling, where your furnace turns on and off for just a short time to satisfy the thermostat. To prevent damage from short cycling, furnaces will have a reset timer where it won't turn back on for a set amount of time. In the down time, you may experience large temperature swings before the furnace will turn back on. Single stage furnaces are best for budget installations where you are looking for the most economical initial purchase. Dual Stage Furnaces Dual stage furnaces are more efficient than single stage furnaces. It will operate most of the time in a lower stage, about 60-70% of the maximum output. When the temperatures outside become very cold and the first stage is not enough to satisfy the call from the thermostat, the furnace will kick on to its full, 100% capacity. With our car example, this would be if your car could drive at only 35 mph or 60 mph, depending on road conditions. Because the furnace has a lower setting, it can run for longer, preventing the larger temperature swings of a single stage furnace. In addition, two stage furnaces tend to be quieter than single stage counterparts and produce less emissions as they don't run at full capacity most of the time. Two stage furnaces are a great way to upgrade the efficiency without breaking the pocketbook. Modulating Furnaces Modulating furnaces are the most efficient furnaces. It will operate at just about any capacity from 35-100%, based on the call from your thermostat. Using our car example again, modulating furnaces operate just like your gas pedal, accelerating to the desired speed as road conditions allow. Modulating furnaces often run longer, at lower outputs, keeping temperature swings to a minimum. Because the furnace can run at hundreds of different output levels, it can keep your home at a steady temperature within 1°F, whether it is -20°F or 40°F outside. Modulating furnaces are the quietest, most efficient, and provide the highest level of comfort for your home. Furnace Staging Comparison Graph On our graph below, you can see the comparative temperature swings between the types of gas valves on our furnaces. Modulating Graph
February 14, 2019
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