Air Conditioning Air Handler Condensate Leaks, Causes of Mold Problems in HVAC Blower Compartments & Ductwork
InspectAPedia® -
Mold contaminated air conditioning ducts or air handlers: how to find, cure, and prevent moldy ductwork and HVAC systems
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
Questions & answers about leaks in air conditioner or heat pump or furnace air handlers
This air conditioning repair article discusses condensate leaks in
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. We explain the causes, cures, and prevention of air handler condensate or other moisture leaks that lead to rust, damage, and mold contamination in the
air conditioning system.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
The evaporator coil and problems of frost build-up in the air handler are also reviewed. Readers concerned with mold contamination in heating and air conditioning air handlers and ductwork should see both BLOWER LEAKS, RUST & MOLD and PARTICLE & MOLD LEVELS in DUCTWORK where we describe how to test HVAC systems and ductwork for mold. Mold in HVAC ductwork is also discussed at WHY DOES MOLD GROW in INSULATION?.
If your air conditioning or heat pump 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.
BLOWER LEAKS, RUST & MOLD - Air Conditioner Air Handler Rust, Condensate Leaks, Wet Insulation, & Mold Hazards
The photograph shows quite a bit of rust on components inside this air handler. More significantly were stains indicating that condensate had blown off of the evaporator coil or otherwise spilled into the air handler cabinet
where it had wet fiberglass insulation there.
Wet fiberglass and other wet insulation material form a potential mold reservoir right in the air path.
If an air conditioning system also lacks a good air filter and thus if it also has become
loaded with organic house dust and debris, combined with water where we don't want it this material also forms a possible growth medium for toxic or allergenic mold inside the air handler or duct work.
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.
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.
Mold on HVAC Air Supply Registers
By simple visual inspection (by the naked eye) it can be difficult to know if the black or gray debris on air supply registers is moldy crud or common house dust (see Stains HVAC Supply Registers). . Our photos below show debris deposited on HVAC ceiling air supply registers in a Kentucky building.
In response to a history of a building leak event and odor complaints as well as the appearance of mold on some building walls, we analyzed samples of the dust from the ceiling air supply register shown at left. At right you can see that the domiant particle in the sample was Cladosporium sp. C. sphaerospermum spores were also present in this sample.
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 nor its growth improved by mis-handling of HVAC condensate. 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.
Don't panic even if you do find small amounts of mold in an air supply register. Even in a healthy building we might expect condensate forming on ceiling air supply registers in some conditions, and thus an accompanying growth of small areas of mold. If that's the extent of mold contamination, ordinary household cleaning procedures are sufficient.
Watch out: if the building leak history or complaint history suggest that a larger mold reservoir could be present, including other genera/species of mold, further investigation is warranted.
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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Additional technical contributors & reference sources for this article are listed below.
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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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
"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]
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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