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AIR CONDITIONING SYSTEMS
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CLEANING & Legionella BACTERIA
DUCT SYSTEM DEFECTS
  SUPPLY REGISTERS, & ZONES
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  BALANCING AIR DUCT FLOW
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  INCREASING RETURN AIR
  LOCATION OF REGISTERS & DUCTS
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  WET CORRODED DUCT WORK
  LEAKY DUCT CONNECTIONS
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FAN AUTO ON CONTROLS
A/C REFRIGERANTS
A/C DIAGNOSTIC FAQs
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Photograph of a return air register for commercial office space

How to Increase Air Conditioning or Heating Return Air Flow
AirCondAPedia ^©

How to increase air conditioning or heating return air flow to improve system performance

Defects in return air ducts & registers for heating or cooling systems

Return air adequacy

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This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes How to increase air conditioning or heating return air flow to improve heating or air conditioning system performance. The photograph above shows a return air inlet grille for a commercial office space after the air conditioning return register and ducts were increased in size as part of improvements in the building cooling system. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

The master document, of which this is a chapter, describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

INCREASING RETURN AIR - "Improvements" to "fix" inadequate return air ducts

Adding return air at the air handler

Photograph of added return air cut at basement AHU also may draw flue gases from nearby gas fired equipment

When the cooling ability of an air conditioning system is inadequate, particularly when the volume of air being delivered in the building seems too low, we often see evidence of an attempt to boost heating or cooling air delivery in this "stopgap" manner: we find openings having been cut in the return plenum right at the air handler unit at a combination air conditioning and hot air heating furnace or at an attic or basement air conditioning-only air handler. Indeed this boosts the air coming out of the system if the air handler was "air starved" due to insufficient return ducts in the first place. An example of this poor practice is shown in the photograph.

But this is a very inefficient way to operate the system since a significant portion of the air volume is moving only "one way" from an attic or basement into the cooling unit and out to a remote living area. This is an expensive way to run an air conditioning system: keep taking "new" air, cool it, and blow it where it's wanted. Proper design re circulates air from the occupied space which permits it to be cooled and filtered.

Worse than inefficient, this approach can be dangerous:

Flue gases: may be drawn into the duct system if these "improvement" openings are cut too close to heating equipment, particularly gas-fired furnaces, boilers, and water heaters. We say more about this at UNSAFE OPENINGS below (see link at left).

Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

AIR CONDITIONING SYSTEMS Chapter Index

To continue reading this air conditioning inspection guide, use links to the document chapters at left or below. Links shown in green font indicate where you are in this document.

Technical Reviewers

Daniel Friedman - principal author/editor of the InspectAPedia ^TM Website
Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and for providing a copy of Carson Dunlop Weldon & Associates Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).

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