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How a Condensate Drain Pan Works in HVAC

The condensate drain pan in your heating and cooling system allows moisture to exit the equipment and your home. A properly functioning condensate drain pan protects your HVAC equipment and your home from water damage. Know how your condensate pan works and when to call for help from an HVAC technician.

Understanding a Condensate Drain Pan

During operation, heating and cooling equipment generates condensation. When the cooling process begins, the evaporator coils within your interior HVAC equipment fall to low temperatures and become cold. This allows the coils to absorb heat from the incoming air in order to cool it.

The warm air that enters your system from the home is moist, but that moisture is removed as heat transfer is conducted by the evaporator coils. As your AC extracts moisture from indoor air during the heat transfer process, condensation forms along the evaporator coils. How a condensate drain pan works is by collecting this water as it drips from your air conditioner’s evaporator coils. 

The condensate pan is attached below the evaporator coils. It must be correctly fitted to catch moisture without leaks. Moisture flows to the condensate drain line and out of your home. Starting at the condensate pan, excess moisture from your home’s air is able to exit your home and the cooling process leaves you with the added bonus of dehumidification indoors.

Where Is My Condensate Drain Pan?

Due to the nature of how a condensate drain pan works, it is always positioned with your system’s evaporator coils. Where these components are located depends on the furnace or air handler type you have installed at home.

  • In a vertical application, the furnace or air handler are in an upright position. Usually, they are installed in a home’s garage or a dedicated utility closet. In a vertical application, the evaporator coils are located at the top of the unit, so you are able to find the condensate drain pan just below.
  • In a horizontal application, the furnace or air handler is installed on its side. This installation application is typically seen when the unit needs to be placed in an attic, due to the limited space available in this area depending on roof pitch. Airflow moves from side to side instead of up and down when the unit is installed this way. Find the evaporator coils located beside the furnace or air handler near the return air ducts, and below it you see the condensate drain pan.

How A Condensate Drain Pan Works When There Are Two…

If you happen to have a horizontally installed furnace or air handler in the attic of your home, notice the unit has a second condensate drain pan. Now, your system does not need two condensate drain pans to operate correctly – this second pan is a backup that offers added protection.

Condensate drain pan failure poses a significant risk of water damage in a horizontal HVAC system. With the unit positioned on its side, a condensate pan failure allows water to drip out across the unit, instead of it funneling to a general location as with a vertical HVAC unit. Water leaks from a failed condensate pan in a horizontal HVAC system leads to damaged wood, drywall, ceilings, and insulation.

How a condensate drain pan works if it is the secondary component is to catch water that may leak out across the unit if the primary condensate pan fails. With its own dedicated drain line, it safely catches spilled condensation and directs it out of your home to prevent damage. 

How Do I Tell the Difference Between the Two Condensate Pans?

The secondary condensate pan on a horizontal HVAC unit is much more visible than the primary one located under your evaporator coils, because you are able to see it as it is not encased in the equipment cabinet. It sits below the system and spans the width and depth of the unit with a little extra area just in case.

Condensate Drain Pan Problems

Problems with how a condensate drain pan works often cause a water leak within HVAC equipment and water damage in the home. If you have regular AC tune ups with Douglas Cooling & Heating, our technicians inspect your system’s condensate pan. They look for issues such as:


If not correctly fitted within the system, water leaks outside the air conditioner. This leads to water damage to the surrounding area if the issue is ignored.


Due to the moist environment, mold and mildew may grow. These contaminants, as well as particles in the air, clog the drain pan. This stops the flow of moisture to the drain line and out of the home which impedes how a condensate drain pan works.

Moisture backup results. Depending on the orientation of your HVAC equipment, water backs up into the system. This leads to component damage. In this case, water also spills over the edges of the condensate drain pan and damages the area around your HVAC system.

Don’t risk water damage and mold. These are often expensive restoration projects.


Due to how a condensate drain pan works, it experiences wear and tear just like other HVAC components. Damage allows water to leak. An obvious sign of a damaged drain pan is water or water damage around your HVAC unit.

Additional Signs of Condensate Pan Problems

These symptoms also alert homeowners to the presence of a problem:

  • Higher humidity in the home
  • Odors from the HVAC system
  • Mold growth
  • Higher energy bills
  • No water coming from the condensate drain line

Protect Your Condensate Drain Pan

Prevent water damage to your home and HVAC equipment and ensure your air conditioner runs properly this summer with these tips to protect how a condensate drain pan works. To provide the best care for your condensate pan, take the following steps:

  • Schedule a preventive maintenance tune up so our NATE-certified technicians inspect your drain pan and correct any issues detected.
  • Change your air filter on a regular basis. This keeps contaminants out of the system and prevents clogs. A dirty air filter allows more contaminants to form clogs.

Call Douglas Cooling & Heating for Air Conditioning Services Including AC Tune Ups and AC Repairs

If you have a problem with how a condensate drain pan works in your home’s HVAC system, contact Douglas Cooling & Heating for help. Our NATE-certified technicians perform the repairs your system needs to keep condensation moving out of your house.

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