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Photograph of an inadequate, mis-located single return air duct for a building apartment. Return Air Duct Leaks

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Air leaks or obstructions in return air ducts of an HVAC system:

This article describes the inspection of the defects in return air registers & ducts for heating or cooling systems (HVAC) 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.



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The photograph above shows a single central return air duct located outside of the apartment which the duct system intends to serve. This installation prevents recirculating of air through the air handler for heating or cooling and results in poor air flow and increased heating and cooling costs for the apartment owners.

The master document, of which this is a chapter, describes the inspection of residential air conditioning systems (A/C systems

Return Duct Air Leaks & What They Mean

Crawl space ducts (C) Daniel FriedmanWhen the air conditioning or heating system is in operation, return ducts are under negative pressure (since the blower in the air handler is drawing air in to the cooling or heating unit). at Soffit Cool Air Blast we describe a more egregious case of duct work that was missing entirely.

Take a look at the flooding crawl space and rusty leaky ducts on dirt in our field photo (left). This crawl area suffered from flooding, sewer backups, and mold. This is not a good place from which to draw air into the building.

Missing return ducts mean that:

HVAC Return Air Duct Leaks & Obstructions that Reduce Return Air Flow Rates

Technical note: The D'Arcy-Weisbach equation for pressure and head loss can be used to calculate the actual pressure loss due to friction in a building piping or air duct system. The Engineering Toolbox provides the D'Arcy-Weisbach formula: Δp = λ (l / dh) (ρ v2 / 2)  where Δp = pressure loss (Pa, N/m2), and l = length of duct or pipe (m) and dh = hydraulic diameter (m) and finally, ρ = density (kg/m3). We discuss this formula and also provide supply a table of supply and return duct sizing at
SUPPLY DUCTS & REGISTERS.

Dirty filter blocks air flow (C) Daniel Friedman

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

Or see AIR LEAK NOISES

Or see AIR LEAKS in RETURN DUCTS

Or see AIR FLOW IMPROVEMENT, HVAC

Or see AIR FLOW MEASUREMENT CFM - how to measure HVAC system air flow

Or see INCREASING RETURN AIR

Or see REGISTER & DUCT LOCATION

Or see RETURN AIR FAQs

Or see RETURN AIR REGISTERS & DUCTS - home

Or see UNDERSIZED RETURN DUCTS

Suggested citation for this web page

AIR LEAKS in RETURN DUCTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to ARTICLE INDEX to HVAC DUCT SYSTEMS

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