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How To Perform An Annual Cleaning Of Your Ductless Heat Pump's Outdoor Condenser

by April Carlson

Your ductless heat pump is a low-maintenance component, but an annual cleaning of the outdoor unit's condenser coils and exterior cabinet will provide increased efficiency and a longer unit lifespan. Below is a step-by-step guide to cleaning your ductless heat pump's outdoor unit:

Tools and materials needed

  • Nut driver set
  • Phillips screwdriver
  • 2-gallon pump utility sprayer
  • Garden hose and spigot
  • Shop towels
  • Mold inhibitor solution
  • Grease-cutting dishwashing soap
  • Shop vacuum
  • Paste car wax
  • Wax buffing pad

Step-by-step procedure

1. Disconnect electrical power to the ductless unit - Before performing any type of maintenance on your ductless heat pump, it is critical to disconnect electrical power to the outdoor unit. A failure to do so could cause a serious shock or damage your unit if water accidentally makes contact with electrical components. Depending on the make and model of your heat pump, the unit will be connected to your home's power supply via a pull-out disconnect or another style switch. Be sure to let others in your household know you are performing maintenance to prevent them from accidentally restoring power to the unit.

2. Prepare the condenser coil cleaning solution - The condenser coils on your ductless heat pump serve an important purpose by transferring heat to and from your home, depending on the season of the year. These coils become dirty over the course of the year, and if conditions are right, mold can also develop and build a thin layer that obstructs airflow.

To clean the dirt and mold away from the coils, you can use a simple homemade solution of 1 part dishwashing soap mixed with 20 parts of clean tap water. Be sure to slowly mix the soap and water and avoid agitating the mixture to prevent bubbles from forming. Next, pour the soapy solution into a 2-gallon utility sprayer and pump it up several times to pressurize the spray.

3. Apply the condenser coil cleaning solution - Once the coil cleaning solution is ready to use, carefully remove the cabinet panels that shield the coils, electronics and compressor using a nut driver set. Set the panels aside in a safe location and begin to apply the solution. If you see debris, such as leaf litter or dead plants, inside the cabinet, use a shop vacuum to suction all foreign material out of the unit.

After cleaning out debris, the next step is to apply a thick layer of coil cleaning solution to the surface of the coils using the pump sprayer; be sure to spray both the inside and outside of the coils for best results. Allow the layer to sit undisturbed for ten minutes and allow it to dissolve grime and other stubborn material. Following that, spray off the condenser coil with a low-pressure stream of water through the garden hose. Don't use a spray nozzle, as the pressure may bend the thin, delicate fins. Be sure to rinse off any signs of soap, but be careful not to direct the water into the electronics compartment on the unit.

4. Apply a mold inhibitor to the coils - If you notice a problem with mold and mildew developing on your coils, then you will also need to spray the newly cleaned coil surfaces with a mold inhibitor. Mold inhibitors may require re-application within a few weeks, depending upon the climate where you live, so carefully monitor the surface of the coils for new growth.

After applying mold inhibitor, reattach all cabinet panels to the outdoor unit, being careful not to accidentally pinch or cut a wire during the process. Check for a tight fit, but don't force the panels back into position.

5. Wax the cabinet - The outdoor unit contains painted sheet metal that will endure longer if you apply a coat of car wax annually. To apply, moisten the wax buffing pad and dip it into the paste wax; apply the wax using a circular motion. Once the wax has been applied, allow it to dry for a few seconds, then wipe it clean with a shop towel. Power can be safely restored to the outdoor unit once you are finished with cleaning and waxing.

For more tips on maintaining your ductless heat pumps, contact a local HVAC company.