Columbus Gas Furance Service

For a furnace to heat a home accurately and efficiently, it must be sized properly. Furnace capacity refers to the amount of heat the unit can produce, which is measured in BTUs (British Thermal Units). Residential furnaces are usually between 60,000 and 100,000 BTU output.

To determine the right size furnace for your home, the home’s heating load must first be determined. HVAC professionals use Manual J calculations to determine heating load, which consider many attributes of the home and how it gains or loses heat energy, including square footage, number of rooms, ceiling heights, exposure, roofing material, and color, number of windows and doors, number of occupants, and more.

It is critical to have your new furnace sized based on this calculation. A furnace that is too small or too large for your home will waste energy and do a poor job of keeping your home comfortable. Undersized and oversized furnaces often suffer more breakdowns and won’t last as long as a correctly sized furnace.

AFUE is the acronym used to show a furnace’s energy efficiency rating, which stands for Annual Fuel Utilization Efficiency. This percentage tells you how efficiently the gas furnace uses the gas energy it takes in. Lower AFUE furnaces produce more waste as they heat a home compared to higher efficiency units. Therefore, using lower-efficiency furnace models will cost more to heat homes than high-efficiency units.

80% AFUE is the minimum efficiency available for new natural gas furnaces, but the higher the number, the more efficient the furnace. Efficiency ratings go as high as 98% AFUE! New gas furnaces that are ENERGY STAR qualified offer an AFUE of 95% or greater. Compared to minimum efficiency gas furnaces, choosing an ENERGY STAR-rated model will save you at least 15% on heating costs.

The heat exchanger is a key component of a natural gas furnace. It contains the combustion gases that produce heat. As air passes over the heat exchanger, it safely absorbs the heat from combustion gases. It is important that the combustion gases be kept out of the air supply, as carbon monoxide exposure can be deadly.

A single heat exchanger is always found in a gas furnace. Many high-efficiency natural gas furnaces also come with a secondary heat exchanger. The secondary heat exchanger continues to use latent heat from the combustion gases, which would be vented out in a system with only one heat exchanger. Furnaces with two heat exchangers are more energy efficient, harnessing more heat from the fuel the system consumes. Gases turn into water vapor and condensation in the secondary heat exchanger, so these furnaces will have a condensate drain to expel the liquid byproducts.

Today’s furnace and heating technology allows for multi-stage operation, providing various levels of heat output for improved comfort control and energy efficiency. Operation stages refer to the speed the blower motor runs to send heated air throughout the house.

• Single-stage furnaces have blowers that run at only one speed. The furnace always runs at full capacity, which isn’t always the most efficient.

• Two-stage furnaces have blowers that can run at two different operating speeds, high and low. Normally, the furnace will run at a low speed for energy efficiency, but the high-speed option can be used when the furnace needs more power to keep the home comfortable. High speeds usually only run during very cold weather when the temperature differential is larger between indoor air and outdoor air. Low-speed operation is much quieter, offering a better user experience.

• Variable speed blowers have electronically commutated motors (ECMs) that operate the blower at varying speeds depending on the heating needs of the home. Variable speed technology can speed up or slow down the blower for precision heating distribution. Furnaces with this feature are more energy efficient with higher AFUE ratings. They use less energy, operate quietly, and provide a better balance between air temperatures and relative humidity inside the home.

Furnace models are available with fixed, two-stage, or multi-stage gas valves that control the amount of natural gas used during operation.

• A single-stage or fixed gas valve always releases natural gas into the furnace at the same rate. Essentially, the furnace works at a fixed capacity, which burns the same amount of fuel no matter the conditions. These furnaces are the least energy efficient with the lowest AFUE ratings.

• Two-stage gas furnaces have gas valves that can vary gas output between a low and high stage, which is 70% and 100% output. Normally, the furnace will run at the lower stage to save energy, but the high stage can be used when necessary to heat the home comfortably.

• Multi-stage or modulating natural gas furnaces run at varying speeds of gas output, electronically adjusting the burner flame intensity to deliver the precise amount of heat needed in the home. Low operation is used most often to conserve energy, but the furnace will automatically adjust and run at higher stages when more heat is needed. These units are the most energy efficient with the higher AFUE ratings.