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Air Conditioning Air Handler Cooling Coil Blockage InspectAPedia®  -     Dirty or blocked air conditioner cooling coils (evaporator coils), how to diagnose & repair Frost build-up on evaporator coils - its effect on cool air flow and 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 problem of dirt or debris blockage of the air conditioning system's cooling coil or evaporator coil in an air conditioning system air handler, how the dirt gets there, what problems it causes, how to clean a cooling coil (or evaporator coil), and how to prevent future dirt on the coil.

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 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.

BLOCKED COOLING COIL - Air Conditioner Evaporator Coil Blocked by Debris

Here is a close up photograph showing how fibers in building dust readily cross the blades of the cooling coil and how the fibers themselves then collect smaller particles to rapidly block air flow across the coil. The same principles that make an air filter work can also clog the cooling coil of an air conditioning system. As a cooling coil (or evaporator coil) in an air conditioner becomes blocked with dust and debris the air flow across the coil is reduced. This reduced air flow (in cubic feet per minute or CFM) across the coil means that the cooling capability of the whole air conditioning system is reduced.

How do we clean a dirty air conditioner or heat pump cooling coil or evaporator coil? See DIRTY COIL CLEANING PROCEDURES.

What Else Causes a Blocked Air Conditioning Evaporator Coil?

Air Conditioner Evaporator Coil Frost or Ice Formation: When the coil becomes sufficiently blocked with debris as to slow down the air flow enough, the coil may actually become so cold that the condensate forming on its surface freezes, completely blocking the coil.

That's because the rate of release of refrigerant into the evaporator coil was designed with an assumption of a sufficient volume of air moving across the coil to keep it from becoming too cold.

When the surface temperature of an air conditioning cooling coil drops below 32 degF or 0 degC, condensate forming on the coil surface begins to freeze, leading to sometimes some pretty weird behavior of the cooling system as we discuss at FROST BUILD-UP where we explain that there can be more than one reason that a cooling coil ices-up but none of those conditions is desirable.

Damaged air conditioner coil fins: can occur on both the evaporator (cooling) coil and the outside condensing coil. See CONDENSING COIL FINS, SUPPORT PADS for discussion of repairing bent or damaged coil fins. Only in extreme cases will fin damage be so severe that air flow across the cooling coil is severely blocked - enough to cause loss of function or coil icing.

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• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
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• Additional technical contributors & reference sources for this article are listed below.

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
AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
CONDENSATE HANDLING
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.
• 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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