Residential Air Handling Unit

A residential air handling unit is basically an electric furnace for your home. The air handling unit, also referred to as an AHU, is part of your home’s HVAC system. AHUs are also commonly called Air Handlers. They consist of an air filter, a blower fan, a refrigerant coil, electric heating elements, and various control components. Are you familiar with the role that a residential furnace plays in your HVAC system? An AHU plays a similar role. Call us today at 402-238-2425 for more information on installing or servicing an air handling unit in your home.

Residential air handling units are often installed in homes that have a heat pump. In this case, the AHU is used in place of a traditional gas furnace. It is also common for a home with a heat pump to have a gas furnace and not have an AHU. Whether the home has a gas furnace or an electric furnace (an AHU) is based on the home builder or home owner preference. We also see AHUs installed in more rural locations where natural gas is not an option. Making use of electric heat has some advantages over using a propane furnace if natural gas is not available. Gas furnaces are assigned efficiency values for AFUE.

The image below shows a traditional furnace and air conditioner for residential applications. An air conditioner has three components. The outdoor unit that houses the compressor and condensing coil is one part. And the indoor refrigerant evaporator coil is the second part of the A/C unit. The evaporator is shown physically on top of the furnace. The third part of the air conditioner is the refrigerant line set that connects the outdoor unit with the indoor evaporator coil. Refrigerant line sets consist of a larger diameter copper pipe and a smaller diameter copper pipe. The larger diameter pipe passes refrigerant vapor. And the smaller diameter copper pipe passes refrigerant liquid.

Image of home furnace and air conditioner


The return air duct in the image above brings return air from various return grills in the home back to the furnace. The return air is pulled across the furnace air filter by the operation of the furnace blower. The blower then forces the air up through the furnace and then through the refrigerant evaporator coil. And the now conditioned air travels through the supply ducts to the various supply registers in the home.

The image below shows an air handling unit that can be used instead of a furnace. Return air from the house enters a metal box that is normally positioned under the AHU. Return air is drawn up through the air filter and across the refrigerant evaporator coil. The air is then drawn through the blower and up across the electric heating elements. Conditioned air then exits the top of the AHU and passes into the supply air duct.

Image of residential air handling unit


The numbered components in the image above correspond to the following.

  1. Housing insulation
  2. Blower Motor and wheel
  3. Metal box surrounding AHU
  4. Refrigerant vapor line leaving the evaporator
  5. Condensate pan
  6. Electric heat pack
  7. Refrigerant metering device (TXV)
  8. Refrigerant evaporator coil


The arrangement of the refrigerant indoor coil in Residential Air Handling Unit normally differs from the arrangement in a natural gas furnace. The image of the traditional furnace and air conditioner and the image of the AHU illustrate this. In most natural gas furnace applications, the refrigerant indoor coil is located above the furnace. In the case with an air handling unit, the refrigerant indoor coil is normally located in the lower compartment of the air handler. In an AHU, return air is pulled through the air filter at the bottom of the AHU, and then the indoor refrigerant coil. Then the air is pulled through the blower and then is directed up through the electric heating elements.

There is a technical basis for the indoor refrigerant coil being placed before the electric heating elements in an air handler. We want all of the heat that is able to be released from the heat pump indoor coil to be transferred into the air stream. The heat pump transfers all it’s heat to the air stream, and then if additional heating is required, the electric heating elements are energized. If the electric heat came first and then the heated air passed through the heat pump indoor coil, the heat pump would not be able to operate correctly. The refrigerant pressures and temperatures would be operating outside of normal parameters. And the heat pump would not work correctly. This would result in inadequate heating of the home and not be a good way to operate the HP.

This is also the reason why a heat pump combined with a gas furnace necessitates that the gas furnace and the heat pump never operate in heat mode at the same time. The heat produced in the furnace would interfere with the operation of the heat pump.

As a side note, some residential occupants do not favor the heat produced from an air handling unit. A natural gas furnace produces hot air that travels through the supply ducts. The electric heat elements and/or heat pump output heat from an air handler is not as hot as a gas furnace. The air from the supply vents is considered by some to be warm instead of hot.

The photo below shows the components in the upper compartment of a Residential Air Handling Unit. Actually, the photo is of a geothermal heat pump unit, but the component arrangement in the upper compartment is similar in a geothermal heat pump unit and an air handler.

labeled components of a residential air handling unit


The photo below shows the coiled electrical resistance heating elements. They are resistive heating wires coiled up to increase the heat density. And the heating elements are contained within a metal box within the unit or the duct.

Electric heating elements from AHU or Geothermal heat pump


The thermal limits in the photo below are safety devices within the electrical circuit for the heating elements. They shut down the circuit if there is a problem with the heat elements.

electric heating elements in AHU showing thermal limit

The photo below shows a refrigerant coil that located in the lower housing of the AHU. Refrigerant passes through the copper tubing or aluminum tubing within the coil. Air passes through the coil and is conditioned. Refrigerant coils are selected to match with the outdoor unit based on tonnage.

evaporator coil from bottom housing of AHU


Recommended Equipment

Trane TEM Residential Air Handling Unit (M series AHU)

Trane TEM Residential Air Handling Unit (M series AHU)


The M Series air handlers combine affordability and flexibility to work with the complete range of Trane heating and cooling products. So you get the reliability of Trane and the options to work within your specific system and budget.

  • Features an all-aluminum coil that’s more durable than standard copper.
  • TEM6 model features a variable speed motor and Comfort-R technology for more efficient home comfort.
  • Rigorously tested parts and components that are made to last.



The all-aluminum coil found in the M Series residential air handlers is exponentially more durable than standard copper coils, which are susceptible to formicary corrosion. These all-aluminum coils ensure families stay comfortable indoors all year long, no matter what the weather outside.


Rust prevention

Trane residential air handlers come with a no-rust polymer drain pan along with galvanized cabinet features to keep things running and looking good for a long time.


Matched options made right

The introduction of the M Series residential air handlers allows more flexibility for addressing special applications for all of your heating and cooling needs. Additionally, The TEM6 residential air handler has a variable speed motor, and Comfort-R technology, offering efficient home comfort at a price that is easy on the wallet.

Trane M Series air handlers offer a variable speed motor and Comfort-R technology for reliable comfort and efficiency, like only a Trane can. The M Series air handler includes:

  • Variable speed blower motor
  • Comfort-R humidity control
  • 4-way convertible line
  • Galvanized steel cabinet
  • Optional electric heat
  • All-aluminum coil
  • No-rust polymer drain pan
  • Cooling and heat pump systems available



Trane TAM Residential Air Handling Unit (Hyperion series AHU)

Trane TAM Residential Air Handling Unit (Hyperion series AHU)


The extraordinary Trane Hyperion™ air handler represents a substantial advance in air handling technology. A double-walled cabinet and our exclusive Trane Vortica™ blower ensures reliable, ultra-quiet operation.

Refrigerator-styled insulation made without exposed fibrous material, virtually eliminates sweating, condensation and airborne particles for a safer home environment. Trane Vortica™ blower provides reliable, ultra-quiet operation. Double-walled cabinet eliminates the need for exposed insulation, preventing energy loss and reducing its carbon footprint.



The all-aluminum coil found in this new line of air handlers is exponentially more durable than standard copper coils, which are susceptible to formicary corrosion. This ensures families stay comfortable indoors all year long, no matter what the weather outside.


Double-walled construction

The double-walled cabinet eliminates the need for exposed insulation and helps prevent energy loss with the use of airtight plugs instead of conventional knockouts. This reduces the unit’s carbon footprint and provides a cleaner environment.


Quiet comfort

Thanks to the exclusive Trane Vortica™ blower, the new Hyperion™ air handler provides homeowners with reliable, ultra-quiet operation, so they can hear each other instead of the heating and cooling system.


Better, cleaner air

Add Trane CleanEffects™ to your system for advanced air filtration that removes more dust, pollen and other irritants from conditioned air for a cleaner, healthier, more comfortable home.


Every Trane Air Handler is packed with high-quality components. Each helps ensure that time after time, your unit will provide total comfort your family can rely on. The Hyperion™ includes:

  • Uniquely designed cabinet
  • Fully enclosed insulation
  • All-aluminum coil
  • Vortica™ blower motor
  • Heating options for either hydronic or electric heat
  • Corrosion-resistant finish
  • “No leak” drain pan made from rust-resistant composites and built with a gradual slope


A Trane AHU Product Brochure is available here.  Also check out the Trane website here for additional information about Trane AHUs.

Accurate Heating & Cooling installs and services all makes of residential air handling equipment. Call us today at 402-238-2425 to schedule an appointment. Check out what our customers are saying about us on our customer testimonials page. We can talk with you about performance differences between traditional natural gas furnaces and electric AHUs. We can also talk with you about the differences between heat pumps and air conditioners. We also can upgrade any of your current HVAC accessories.

Indoor air quality is a growing concern for many home occupants. There are many different air filter options available as well as electrostatic air cleaners and air scrubbers. Home humidification is another component of high indoor air quality. Both heat pumps and air conditioners dehumidify the air during the summer months. There are many helpful tips for homeowners to perform maintenance on their HVAC system to help keep it running all season long. And give us a call to schedule your seasonal HVAC equipment clean & check. We sometimes get asked if annual furnace maintenance is necessary.