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How to Increase Air Conditioning or Heating Return Air Flow InspectAPedia®  -     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

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 2009 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

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 extra return air 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:

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Use links just below or 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 & HEAT PUMP SYSTEMS
AIR CONDITIONER COMPONENT PARTS
CONTROLS & SWITCHES
A/C DIAGNOSTIC FAQs
A/C TYPES, ENERGY SOURCES
A/C REFRIGERANTS
AIR CONDITIONER BTU CHART
SEER RATINGS & OTHER DEFINITIONS
OPERATING COST
SYSTEM OPERATION
OPERATING TEMPERATURES
OPERATING DEFECTS
LOST COOLING CAPACITY
COMPRESSOR & CONDENSING COIL
AIR HANDLER UNIT
AIR FILTERS for HVAC SYSTEMS
CONDENSATE HANDLING
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
DUCT SYSTEM DEFECTS
  ASBESTOS HVAC DUCTS
  DUCT ROUTING & SUPPORT
  BALANCING AIR DUCT FLOW
  FIBERGLASS HVAC DUCTS
  FIRE DAMPERS in DUCTWORK
  GOODMAN GRAY FLEXDUCT
  INCREASING RETURN AIR
  LEAKY DUCT CONNECTIONS
  LOCATION OF REGISTERS & DUCTS
  OWENS CORNING FLEXDUCT
  OWL FLEXDUCT
  RETURN AIR REGISTERS & DUCTS
  SUPPLY REGISTERS, & ZONES
  Transite Pipe HVAC Ducts
  UNDERSIZED RETURN DUCTS
  UNSAFE DUCT OPENINGS
  VIBRATION DAMPERS
  WATER & ICE IN DUCT WORK
  WET CORRODED DUCT WORK
  ZONE DAMPER CONTROLS
ENERGY SAVINGS in BUILDINGS
FAN AUTO ON CONTROLS
A/C REFRIGERANTS
A/C DIAGNOSTIC FAQs
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
CRITICAL DEFECTS
FURNACES WARM AIR HEATING SYSTEMS
INDOOR AIR QUALITY IMPROVEMENT GUIDE

• 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.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) 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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