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Air Conditioning Air Handler Unit Leaks, Mold Problems &: Repairs InspectAPedia®  -     Air Conditioning air handler blower fan 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.

If your air conditioning system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & 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.

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AIR CONDITIONING & HEAT PUMP SYSTEMS
AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
  Indoor A/C Components
  Outdoor A/C Components
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
  Air Filter Location
  Dirty Air Filter Problems
  Missing Air Filters
 OPTIMUM INDOOR AIR FILTERS
 CONTINUOUS BLOWER FAN OPERATION
 AIR FILTER EFFECTIVENESS
 FIBERGLASS & AIR FILTERS
 SOURCES FOR AIR FILTERS
AIR HANDLER UNIT
  ADDING A/C: RETROFIT SIZING
  BLOWER LEAKS, RUST & MOLD
  COOLING COIL DEFECTS
  DIRTY A/C BLOWERS
    Leaks, Rodents In Air Handlers
    Mold Growth in Air Handlers
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
CONDENSATE HANDLING
  DRIP TRAY DEFECTS
  CONDENSATE LEAKS
  CONDENSATE PUMPS
  CONDENSATE DRAINS
  CONDENSATE TRAY CLEANING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
  DAMAGED COOLING COIL
  DIRTY COOLING COIL
  DIRTY COIL CLEANING PROCEDURES
  FROST BUILD-UP
DATA TAGS on AIR CONDITIONERS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
ENERGY SAVINGS in BUILDINGS
EVAPORATIVE COOLING SYSTEMS
FAN AUTO ON Thermostat Switch
HEAT LOSS (or GAIN) in BUILDINGS
HUMIDITY LEVEL TARGET
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
  What to check first
  Compressor failure diagnosis
  Duct & Air Handler diagnosis
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
SWAMP COOLERS
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books

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

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