Photograph of  a 1930's supply duct in active use. Find & Fix Air Conditioning or Heating Supply Air Duct Leaks or Obstructions

  • SUPPLY DUCT AIR LEAKS - CONTENTS: Checklist for Finding HVAC Supply Air Leaks & Obstructions. Heating & Cooling Ducts - Supply Registers & Zones. Air Conditioning (or Heating) Duct Defects. The D'Arcy-Weisbach equation for pressure and head loss applied to HVAC ducts.
  • POST a QUESTION or READ FAQs about inadequate supply air in HVAC duct systems and its effect on heating or cooling air flow adequacy
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Guide to heating & cooling duct work supply air flow adequacy, flow rate, temperature, and related problems.

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes the inspection of heating and air conditioning (HVAC) duct registers & zones for defects such as missing air conditioning cool air supply or return air registers, undersized air conditioning duct openings, improper cooling duct routing, cooling (or heating) air duct corrosion, leaky air duct connections, defective heating or cooling ductwork materials such as Goodman gray flex-duct, some Owens Corning Flex-duct, and asbestos-containing air conditioning or heating duct work.

The photograph above shows a 1930's heating and cooling air supply register still in active use, but with leakage around the register which transmitted odors and mold from the building basement.

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HVAC Supply Air Duct Leaks & Obstructions - Theory & Practice

Crimped cooling duct (C) Daniel FriedmanBlockages or crimps in HVAC ducts (photo at left) restrict air flow and in severe cases can cut it off entirely.

Leaks in HVAC cooling or heating air supply ducts mean that cooling or heating costs are increased, since the HVAC system needs to run longer to reach the desired indoor temperature and humidity.

[Click to enlarge any image]

Where more severe supply air duct leaks are occurring, some areas of the building or even the entire building may receive no heated or cooled air at all, even though the equipment is running.

Below we list a catalog of common explanations for inadequate air flow from an HVAC duct system.

Watch out: But keep in mind that even this apparently accurate calculation of the effect of piping on air pressure and airflow loss will not include the effects of leaks or obstructions in the building return air or supply air duct system such as the following:



Continue reading at LEAKY DUCT CONNECTIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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