Monthly Archives: December 2013

Forced Air Furnaces: See How They Work

According to the U.S. Department of Energy, the most common method of heating residences and commercial buildings throughout the nation is with a forced air furnace. With an astounding level of practicality and functionality, forced air furnaces are efficient, easy to install and offer several other benefits. Whether you’re in the market for a new forced air furnace or simply looking for more information about the unit, check out the following information to see how they work.

How Forced Air Furnaces Work

The forced air furnace pulls colder air through the ductwork running throughout your home into the furnace where it’s heated. Once the furnace heats the cool air, the heated air is then sent back through different ductwork and pushed out through heat registers to warm your home.

Basic Parts of a Forced Air Furnace

  • The thermostat communicates with the furnace, telling it when to turn on and off. When temperatures drop below the thermostat setting, the furnace will turn on. When the temperature reaches the desired setting, the thermostat will turn the furnace burners off.
  • The oil or gas burner is the source of heat for the system, which communicates with the thermostat.
  • The heat exchanger is a metal box that houses the combustion of gases from the burning oil or gas. The exhaust exits through a vent in the heat exchanger and is sent outside.
  • The blower, which is located between the furnace itself and the cold air return, pulls the cool air from your home and sends it into the furnace through the cold air return. The cool air will circulate around the heat exchanger until it’s warmed. It’s then sent to the air plenum located on the output side of the furnace.
  • In your home, there are both return ducts and supply ducts. The return registers accept cool air in your home through the cool air ducts. The warm air is then blown through the warm air ducts into your rooms once it’s been heated and sent to the air plenum.
  • Your forced air furnace also has a blower, which is controlled by the fan limit switch.

Benefits of Forced Air Furnaces

  • Compatible – The biggest advantage of a using forced air furnaces is the sharing of ductwork and vents with air conditioning units.
  • Cost – With few component parts, the cost of forced air heating systems is fairly low compared to other systems, such as radiant heating. The low cost feature makes this type of heating solution the prime choice for builders wanting to keep the cost of materials low and for the cost-conscious homeowner.
  • Energy efficient – Although radiant heating systems generally offer a higher energy efficient rating than forced air furnaces, a forced air heating system can provide a high energy efficiency rating. Your furnace’s energy efficiency is measured by the annual fuel utilization efficiency (AFUE), which represents the amount of fuel your furnace uses and wastes during the year to heat your home. The higher your AFUE, the more efficient your furnace. Older furnaces can have an AFUE as low as 65, which means that only 65 percent of the fuel is converted into usable heat. Today’s furnaces can have an AFUE rating up to 98, which means significant savings on your heating bill. Keep in mind the AFUE rating will decrease over time, especially if it’s not well maintained.
  • Better with programmable thermostat – Programmable thermostats work at a higher efficiency with forced air heating systems than they do with radiant systems. While the pipes of a radiant heating system take a much longer time to heat up and need more time to match the requests of the thermostat, forced air furnaces respond to programming or temperature requests and changes almost immediately. As a result, forced air furnaces waste much less energy than radiant heating systems.

If you have additional questions regarding a forced air furnace or for other home comfort concerns, contact the professionals at Keith Air Conditioning. Our team of experienced professionals have been serving the Baldwin-Mobile area for over 50 years.

High Efficiency HVAC Equipment Provides Year-Round Comfort

If you’re planning to replace your existing HVAC system, doing so with high efficiency HVAC equipment will increase your comfort without raising energy bills. Heating and cooling equipment that offers high efficiency is labeled with the Energy Star or Most Efficient label, and these systems have met strict criteria to earn this designation.

Since conditioning your home uses about half the energy you use each year, opting for systems that lower your consumption translates to lower utility bills. Although such equipment costs more than the systems that meet the minimum standards for efficiency, the payback when replacing is faster.


A combustion furnace’s heating performance is reflected in its annual fuel utilization efficiency (AFUE) rating, which expresses how much of the fuel it consumes is actually used for home heating. The minimum stands at 78, which translates to a system that wastes 22 percent of the fuel it uses. To be considered high efficiency, the furnace must have an AFUE of 90, wasting just 10 percent of the fuel it uses.

The most efficient furnace on the market—a condensing furnace—uses close to 99 percent of the fuel it consumes. This kind of furnace incorporates a second heat exchanger to remove the heat from the water vapor burned gas creates. Instead of going up the flue or chimney, it’s used for heating your home.

Other high efficiency HVAC equipment that’s suitable for heating your home in our climate include air handlers that contain variable speed motors, which use much less electricity than a single-speed motor does. You’ll benefit winter and summer because these systems offer more comfort and improved indoor air quality. The motor runs more slowly and quietly.

Heat Pumps

This is often the high efficiency HVAC equipment of choice for our region since winters are mild. The minimum efficiency for cooling stands at a seasonal energy efficiency ratio (SEER) of 13 and a heating season performance factor (HSPF) of 7.7 for heating. To qualify for high efficiency status, the SEER must be 14.5 and the HSPF must be 8.2 or more.

Air Conditioning Systems

Central air conditioners must meet the same SEER requirements that a heat pump does.

Installation Matters

While installing high-efficiency equipment is fundamental to achieving comfort and energy savings, how it’s installed makes a difference in its performance. Your HVAC contractor should cover these areas during the selection and installation process:

  • Correct sizing – Avoid hiring an HVAC contractor who simply looks at the size of your existing equipment and goes by that. Sizing the system should be done with software tools called Manuals J and D. These take into account the conditioning load of your home and the ductwork and its configuration. A system that’s too large runs in short cycles more often during the day and drives up energy bills while increasing wear on the parts. One that’s too small won’t keep your home as comfortable when it’s exceptionally hot or cold.
  • Energy efficiency upgrades – Improving attic insulation, increasing window energy efficiency and sealing air leaks will improve the system’s performance.
  • Placement – The outdoor condensers for air conditioners and heat pumps should be placed in your yard where sunshine is limited to reduce cooling costs. The condenser has to get rid of the heat from your home, and shielding it from sunshine helps the hot refrigerant cool down.
  • Ductwork – The contractor needs to conduct a thorough evaluation of your ducts to verify that they’re an adequate size for the new equipment and have few, if any, leaks. Leaking ducts will reduce the performance of high efficiency HVAC equipment substantially. The air will enter places in your home where it’s not needed, driving your conditioning costs up. Depending on the size of the leak or breach, the wasted energy could be substantial.
  • Refrigerant levels – Heat pumps and air conditioners use refrigerant as the conditioning mechanism. Improper amounts reduce the efficiency of either system, and if the level is too low, could even cause your system to stop working.
  • Maintenance – Keeping the air filter clean for the air handler and the outdoor condenser clean and free from nearby vegetation improves operating efficiency, as does annual professional maintenance.

To learn more about high efficiency HVAC equipment in the Mobile and Baldwin County area, contact Keith Air Conditioning, Inc. today.