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• Air Conditioning air handler unit (AHU) leaks and risk of toxic mold
• Air conditioning air handlers - Fan Coil Unit Inspection, Diagnosis, Repair, Replacement

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" discusses the air conditioning system air handler units, blower units, or AHU's, (also called fan coil units) including the air conditioner blower fan, air conditioning system filters, and the causes, cures, and prevention of air handler leaks that lead to rust, damage, and mold contamination in the air conditioning system. The evaporator coil and problems of frost build-up are reviewed. We explain how an air conditioning service technician will diagnose certain common air conditioning system failures or defects. We include photographs to assist readers in recognizing cooling system defects. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © 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.

BLOWER LEAKS, RUST & MOLD - Air Conditioner Air Handler Rust, Condensate Leaks, Wet Insulation, & Mold Hazards

These two photographs show more clearly that condensate has been overflowing the condensate collector inside the air handler.

This air conditioning condensate water has gone where we don't want it: onto the fiberglass insulation and into the duct system. The moldy looking material growing on the foil face of the insulation was a rather common Cladosporium cladosporoioides mold which we often find inside air handlers and duct systems that have been wet like this.

While Cladosporium sp. is the most common mold found on earth and while it's just about everywhere, for some people this is an allergenic mold. We don't want it being blown around by our air conditioning system. See MOLD CONTAMINATION LEVELS and Mold Atlas & Particles List for a description of the health effects and air quality complaints associated with various kinds of mold.

The right hand photo is a close up showing evidence that the fiberglass insulation has been wet in this area - note the rust stains? We often find more problematic molds in the Aspergillus sp. genus where fiberglass insulation has been wet, even when no mold was visible to the eye.

Photographs of mold growing right on an air conditioner squirrel cage blower fan are in our article at Mold Growth in Air Handlers.

More information about the potential of problematic mold growth in fiberglass and more example photographs of this event can be read at Mold in Fiberglass in Insulation at this website.

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 SYSTEMS
A/C COMPONENTS
  Indoor A/C Components
  Outdoor A/C Components
A/C DATA TAGS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCES
AIR CONDITIONER BTU CHART
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
  DIRTY A/C BLOWERS
  DIRTY COOLING COIL
  FROST BUILD-UP
  BLOWER LEAKS, RUST & MOLD
  ADDING A/C: RETROFIT SIZING
CLEANING & Legionella BACTERIA
  CONDENSATE TRAY CLEANING
  Should we disinfect
  Wisconsin Protocol for Cleaning A/C
  Legionella sp. Health Concerns
  What are Legionella
  Where do Legionella sp. occur?
  Recommended Level for Legionella sp.
  How When to Test for Legionella sp.
  Legionnaires' Disease Information from CDC
COMPRESSOR CONDENSER
CONDENSATE HANDLING
  DRIP TRAY DEFECTS
  CONDENSATE LEAKS
  CONDENSATE PUMPS
  CONDENSATE DRAINS
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
  ASBESTOS HVAC DUCTS
  DUCT ROUTING & SUPPORT
  BALANCING AIR DUCT FLOW
  FIBERGLASS HVAC DUCTS
  GOODMAN GRAY FLEXDUCT
  INCREASING RETURN AIR
  LEAKY DUCT CONNECTIONS
  LOCATION OF REGISTERS & DUCTS
  OWENS CORNING FLEXDUCT
  RETURN AIR REGISTERS & DUCTS
  SUPPLY REGISTERS, & ZONES
  Transite Pipe HVAC Ducts
  UNDERSIZED RETURN DUCTS
  UNSAFE DUCT OPENINGS
  VIBRATION DAMPERS
  WET CORRODED DUCT WORK
DUCT INSULATION, Asbestos Paper
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
FAN AUTO ON Thermostat Switch
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
REFRIGERANTS
  REFRIGERANT LEAK DETECTION
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books

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.).
• Wikipedia provided background information about the definition of HEPA and airborne particle interception.

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Contact Daniel Friedman for website content suggestions or for fee-paid consulting

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