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Return Air Registers & Ducts for Heating / Cooling Systems InspectAPedia®  -     Defects in return air ducts & registers for heating or cooling systems Return air adequacy Air Conditioning (or Heating) Duct Defects

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" 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.

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.

© 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.

Basement Air Handler, No Return Air Ducts, All Return Air Taken at Air Handler

One-Way Cooling or Heating Systems: Some retrofit HVAC installers simply cannot figure out where to place return ducts, so they are just omitted such as shown in the two photographs here. For example a basement or crawl space air handler may be found with no return duct connections at all.

Rather you'll see that the return plenum is simply open to the basement or crawl space. The second photograph confirms that wet, possibly moldy debris enters the HVAC system at this single point basement air return to the blower unit. In the foreground of the photograph you can see our Burkard (TM) air sampling machine being used to take a look at what the basement is sending into the home's ductwork and living space.

This forms a "one way" cooling or heating system - 100% of the air is drawn from the area around the air handler, cooled (or heated) and blown "one way" into the occupied space. This is the most inefficient design possible as well as possibly a dangerous one (see "Flue Gases" above).

Preferably return air is drawn from the heated or cooled space. Taking "new" makeup air from an unheated space, heating it, and blowing it "one way" into the heated area has to be a more costly way to heat a building. For better indoor air quality and as recommended by ASHRAE, commercial and large residential heating and cooling systems may include apportion of outdoor fresh air input to the duct system as well.

Attic Air Handler Air Conditioner Return Duct Defects

This photograph shows a typical black, large-diameter return flex-duct moving building air to the air conditioning system air handler unit located in an attic. Notice the loose fiberglass insulation around the base of the large-diameter black flex-duct carrying return air? Poor connections at this location were pulling loose fiberglass insulation fragments and attic dust and debris into the air handler system. In addition, this poor return duct connection, by leaking attic air into the duct system, increased the air conditioning operating cost by feeding it hot attic air instead of building living space air. This photograph has a couple of other interesting details. Notice that the return duct is partly crimped and thus obstructed as it passes through the site-built building truss? Also, what's that electric motor doing lying askew in the insulation next to the flex-duct? Perhaps the central air return, located in the ceiling of the space below, was placed where previously there had been a ceiling-mounted whole house fan, for which we see the motor, abandoned in the attic floor. Understanding the history of changes made to a building can help interpret the meaning of clues about the building condition. It would be a safer practice to remove the still-connected but un-used fan motor. Either remove the un-used fan circuit wiring completely, or enclose the termination of the un-used wires in a junction box.

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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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