At some point homeowners have encountered the same question, “What furnace size do I need?” Good news, you are not alone.
Several factors need to be considered when choosing the correct furnace size for your home. Doing your homework before making any commitments is important. Purchasing the wrong size or type of furnace can lead to high installation costs and a less efficient heating system.
Here are important facts to help you make the correct furnace size choice.
Capacity
A furnace that is over-sized is as inefficient as one that is too small for the heating area. An overly large capacity furnace will incur heat loss due to a condition called rapid-cycling.
When this occurs, the furnace will start and stop quickly. Certain areas of your home may be warmer than others. The method used by professionals to ensure the proper size furnace is installed in your home is called the Manual J Load Calculations. “It calculates the amount of heating and cooling BTU’s needed for the whole house.”
It incorporates the number of windows and doors along with the type of insulation to measure the size furnace necessary to provide consistent heat for your entire living space. The industry standard for measuring the capacity of a furnace is the BTU or British Thermal Unit.
The energy required to heat one pound of water by one degree Fahrenheit is equal to one BTU. A tag with this number should be in plain view on a new furnace.
Efficiency
The efficiency rating is equally important to the best overall furnace. This measurement is called the AFUE or Annual Fuel Utilization Efficiency rating.
The measurement represents the percent of fuel that converts into heat. A furnace that is the correct capacity, but has poor efficiency will lead to higher fuel costs and possibly need more repairs because of the longer running times to maintain a set temperature.
In 1992, the set standard for efficiency was increased to at least 80 percent for furnaces. Many modern models run as high as 98 percent efficient. The yellow “ENERGYGUIDE” label will have this figure. The Federal Trade Commission requires this be placed on all new furnaces.
Modern Furnace Features
Electronic Ignition
Older furnaces have a constant pilot light. This requires a constant flow of gas resulting in higher energy costs. Modern furnaces have an electronic ignition system which eliminates the need for a constant gas flow.
Two-Stage Gas Valve
The two-stage systems has a lower setting which allows for reduced gas flow when possible. The furnace can switch to the higher gas-flow when necessary. This is more efficient than a single-stage furnace that constantly runs at high capacity.
Variable Speed Air-Handler
The blower runs slower and can operate even if the furnace is shut down. This has multiple benefits. There is a smoother operation which increases the lifespan of the blower and ultimately more even heating through your home. Increased air-filtering is another benefit of this system.
Modulating Gas Valve
There are periods during the day when not as much gas flow is needed in your furnace. The modulating gas valve can make adjustments to ensure only the necessary amount of gas is supplied to your furnace.
Modern furnaces have many features, but capacity and efficiency are crucial when deciding on the right furnace. A correctly sized furnace will keep you and your family comfortable without the high energy costs.
Discuss the project with your HVAC contractor to ensure your new furnace is the proper fit for you. A home energy audit could be the right start for you.
If needed, replacing your old heating system can improve your home’s comfort, efficiency and lower your energy bill. At Alpine Temperature Control in St. George we specialize in just such a thing. Give us a call and we can help you find the right furnace size for your home!
