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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Air handler blower unit leaks & mold hazards: this air conditioning repair article discusses the problem of A/C condensate leaks into air conditioning system air handler units, blower units, or AHU's, (also called fan coil units). We include the air conditioner blower fan, air conditioning system filters in this discussion, and 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. The evaporator coil and problems of frost build-up in the air handler are also reviewed.
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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.
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 dominant 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 mishandling 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.
See PARTICLE & MOLD LEVELS in DUCTWORK where we describe how to test HVAC systems and ductwork for mold.
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