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Special Installation Considerations for Condensing Furnaces

If your old furnace is at the end of its useful life span, and you are installing a new condensing furnace, make sure your HVAC technician follows the special installation procedures required of your new high-efficiency system. You’ll enjoy years of heating comfort, safe operation and energy savings.

Condensing furnaces have two heat exchangers that extract up to 98.5 percent of the heat from exhaust gases, which are wasted up the flue in conventional furnaces. The exhaust gases are condensed and cooled to a temperature that permits sidewall venting through plastic pipes. The condensation process also produces an acidic condensate that must be drained. These are the basic installation requirements of sidewall venting your condensing furnace:

  • The entry/exit points of the pipes should be on the same wall of the home so that air pressure is equal for both intake and exhaust.
  • The entry/exit points of the piping must be sufficiently high off the ground to avoid obstruction from snow accumulation.
  • Avoid installing the pipes beneath a window, and make sure they are at least one foot apart to prevent exhaust gases being drawn into the intake pipe.
  • The screen guard on the pipes should be removed during the heating months to prevent airflow restriction from ice accumulation. Reinstall the guards once the heating months are over to prevent birds and other creatures from building nests inside.
  • The exhaust pipe should be installed with no less than one-quarter inch pitch toward the furnace, with the highest point outside the home. The cooled exhaust gas produces acidic condensate, which must be able to flow back to the trap. If condensate pools inside the piping, airflow may become restricted to the point that the furnace shuts down.
  • Check the drainage tubing from time to time to ensure that it is not restricted by kinks or something placed on it.
  • Ask your heating professional to inspect the ductwork before installing the new furnace to ensure it is sealed and efficiently designed.

For more information on condensing gas furnaces and their installation requirements, contact HVAC & Plumbing Unlimited Heating & Air Conditioning. We serve homeowners in Fairfax and the surrounding area.

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