In a time where technology is always expanding and improving, it seems as though nothing can escape its grasp. Even a simple machine like a furnace is not insulated from improvement.
To break down and simplify the complicated, here is how a furnace works...
Single Stage Furnace:
In single-stage gas furnaces, the gas valve/burner comes on at 100% capacity when the thermostat calls for heat. It stays at full capacity until the inside temperature satisfies the thermostat. Single-stage furnaces offer basic on/off operation. All furnace brands make at least one single stage furnace; most make several. They are the most affordable and are usually found in 80% efficient furnace and furnaces from 90% to 95% efficiency.
Single Stage is typically the cheapest and most common option. Cons are that, depending on your home's layout and ductwork etc., you may find hot and cold spots in far areas of the home. It also can lead to a drafty home due to the way the furnace has to operate to satisfy the commands you enter into the thermostat.
Two Stage Furnace:
Two-stage furnaces feature burners that can fire at 2 different levels, depending on the heating needs of the moment. On low capacity, most 2-stage models run at 65% to 70% capacity. During the course of a normal heating day, the furnace will run on low as much as 80% of the time. It will usually only shift to full capacity if outside temperatures drop quickly or if the thermostat is turned up. Most 2-stage furnaces also use variable-speed blowers to match the capacity of the burner.
The value of 2-stage heating is quieter, more comfortable operation. Running on low capacity produces longer heating cycles. There isn’t a blast of heat that might cause some rooms or areas of the home to become warm, shutting down the thermostat before other areas can become fully heated. In addition, these longer cycles do a better job of filtering air because it passes through the filter more times during the course of a day. If a humidifier is installed in the furnace, these longer cycles distribute more humidity into the home. Finally, a burner and blower fan running on low are significantly quieter than full capacity operation.
These have been available for a few years but now all of the major brands are making modulating furnaces. The gas valves of these furnaces open anywhere from 40% to 100%, depending on the precise need for heat in the home. Some of them adjust in increments as little as .5%. They often begin on very low capacity and ramp up during a heating cycle to meet the demand for heat. They run at less than full capacity almost all the time.
Modulating furnaces take the value of staged heat to the ultimate level. Temperatures within the home are very balanced from room to room. Temperature is often maintained within 1 degree, so you rarely feel fluctuations. These furnaces cost the most of any models and for the expense, you get the most comfortable indoor climate currently possible.
Now You Have All The Options, What Choice Will You Make?
Which type of furnace is right for you? Single stage, 2 stage or modulating furnaces? If saving on equipment is your priority, there are many outstanding single-stage furnaces. Some have multi-speed (not quite variable-speed) fans that come on more quietly and don’t blast cold air at the beginning of the cycle. If you can live with small temperature fluctuations and slight differences from room to room, single-stage models are a good option.
For a balance of cost-savings and comfort, 2-stage furnaces remain the most popular furnaces on the market. They can offer higher efficiencies than single-stage, if needed where you live, and they don’t sport the “bleeding edge” cost of modulating models. If enjoying maximum home comfort is your priority, the new modulating furnaces offer superior climate control and indoor comfort. Consider your heating needs and priorities.
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