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Air conditioning repairs,service, maintenance, estimates

Air conditioning repairs,service, maintenance, estimates in Florida

Air Conditioning Diagnosis, & Repair Guide
InspectAPedia® - ShareThis

* How to inspect, diagnose, & repair central air conditioning systems and heat pumps: A/C repair, lost cooling, insufficient cooling.
* What are the basic air conditioning components?
* Determining air conditioning cooling capacity & energy efficiency
* Troubleshooting air conditioning compressor problems
* Diagnosing air conditioning air handler problems
* Air conditioning condensate problems
* Duct system inspections, defects, repairs
* Cleaning air conditioning equipment & fixing leaking A/C refrigerants

This website explains in detail the inspection, troubleshooting diagnosis, and repair of all types of residential and light commercial central air conditioning and heat pump systems.
Our site offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/Contact.htm.

Page top illustration of a heat pump schematic is provided courtesy of Carson Dunlop Associates and is found in their Home Reference Book. A somewhat simpler schematic of an air conditioning-only system is provided just below.
Photograph of wall convector air conditioner being serviced Photograph of a modern A/C system compressor condenser unit pair Photograph of a modern A/C system indoor air handler unit Photograph of a modern A/C system compressor split system inside air handler

Here we describe how to inspect and repair all types of residential air conditioning systems (A/C systems). Information for home buyers, owners, and home inspectors about A/C or heat pump system problems. The articles at this website describe the basic components of an air conditioning system and then we discuss how to estimate the rated cooling capacity of an air conditioning system by examining various data tags and components. The limitations of visual inspection of A/C systems are described. 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 2010 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

All the detail about air conditioning you want is provided here - ask us if you can`t find something. Let`s introduce the most basic concepts of air conditioning first:
What are the Parts of an Air Conditioning or Heat Pump System and How do Air Conditioners Work?

Air conditioning system schematic (C) Carson DunlopHere is a simple explanation of how an air conditioning system works, with enough detail so that it isn`t simply magic (the schematic of an air conditioner shown at left is compliments of Carson Dunlop) A detailed list and photos of air conditioner components can be seen at AIR CONDITIONER COMPONENT PARTS.

1. A air conditioning or heat pump compressor which compresses low pressure refrigerant gas into a high pressure, high temperature gas. Usually the compressor is in the outdoor portion of an air conditioning or heat pump system. The compressor is basically a high pressure pump driven by an electric motor. The air conditioning compressor is usually packaged in the outdoor compressor/condenser unit illustrated by our page top drawing. See COMPRESSOR CONDENSER, and see REFRIGERANTS

2. A condenser or condensing unit: typically a condensing coil inside which high temperature high pressure refrigerant gas flows, and over which a fan blows air to cool the refrigerant gas back to a liquid state (thus transferring heat from the refrigerant gas to the air being blown by the fan). The condenser unit is basically a coil of finned tubing and a fan to blow air across the coil. Usually the condenser unit is in the outdoor portion of an air conditioning system, often packaged along with the compressor motor discussed above. See COMPRESSOR CONDENSER and see our page top sketch too. The change of state of the refrigerant, from hot high pressure gas to a liquid releases heat, including heat collected inside the building) to the outdoors.

3. A metering device which dispenses liquid refrigerant into an evaporator coil. The metering device may be simply a thin section of tubing (a capillary or "cap" tube) or it may be a bit more sophisticated thermostatic expansion valve (TEV) which includes a temperature sensing control that can open and shut the device against refrigerant flow. See THERMOSTATIC EXPANSION VALVES .

4. An evaporator coil or cooling coil: typically the cooling coil is a section of finned tubing (it looks a lot like a car radiator) into which liquid refrigerant is metered and permitted to evaporate from liquid to gas state inside the coil. This state change of the refrigerant, from liquid to gas, absorbs heat, cooling the evaporator coil surface and thus cooling indoor air blown across the cooling coil. Usually the cooling coil is located inside the air handler. See AIR HANDLER / BLOWER UNITS and articles like DIRTY COOLING COIL. Evaporative cooling systems, or swamp coolers are discussed separately at EVAPORATIVE COOLING SYSTEMS.

5. An air handler and blower unit which provides a fan to blow building air across or through the evaporator coil. The air handler blower fan unit moves building air across the evaporator coil surface in order to condition building air by cooling it (and thus also by removing moisture from the cooled air). See AIR HANDLER / BLOWER UNITS and BLOWER FAN OPERATION & TESTING.

6. A duct system which distributes conditioned air from the air handler in to the occupied space (supply ducts), and which takes air from the occupied space and returns it to the cooling system air handler. See DUCT SYSTEM

7. Heat Pump Systems use the same components we have described just above, with the addition of a reversing valve that in essence permits the system to run "backwards" in cold weather. So in air conditioning mode the heat pump is moving heat from inside the building to outdoors while in heating mode the heat pump is moving heat from outdoor air (or water in some designs) to the building interior. Because the ability of a heat pump to extract heat from outdoor air diminishes at low outdoor temperatures, heat pump systems in northern climates also include a backup or auxiliary heating system. Details of how heat pumps work, are inspected, diagnosed, and repaired begin at HEAT PUMPS.

8. Air conditioner controls and features, which include a room thermostat, electrical switches, fuses or circuit breakers, condensate handling system, and air filters. See OPERATING CONTROLS and AIR FILTERS for HVAC SYSTEMS

For photographs of these various air conditioning and heat pump parts, and for an explanation of where these air conditioning components are physically located, see A/C COMPONENTS which discusses Indoor A/C Components and Outdoor A/C Components
How to diagnose and fix an air conditioning system that is not working

Since the failure of an air conditioner to turn on, loss of air conditioner cooling capacity, reduced air conditioning output temperatures, loss of cool air supply, or even loss of air flow entirely can be due to a variety of problems with one or more components of an air conditioner or air conditioning system, after reviewing the lost air conditioner cooling diagnosis procedures described in this article, be sure to also review the diagnostic procedures at each of the individual air conditioning diagnosis and repair major topics listed just below. To return to our air conditioning and refrigeration home page go to AIR CONDITIONING & HEAT PUMP SYSTEMS.

If your air conditioning or heat pump system has lost its cooling capacity or won`t start select one or more of the diagnostic articles listed below.
Honeywell room thermostat

* A/C REFRIGERANT LEAK DETECTION: how to use a TIF5000 to detect air conditioning refrigerant gas leak. Also see REFRIGERANT LEAK DETECTION and REFRIGERANT LEAK REPAIR and REFRIGERANT PIPING & DISTANCES
* A/C DIAGNOSTIC FAQs: air conditioning system diagnostic FAQs: Q&A about air conditioner repair - a detailed air conditioning system diagnostic checklist
* AIR HANDLER UNIT: problems with the air handler, air filters, and the cooling coil itself
* BACKUP HEAT: on heat pumps, types of backup heat; problems with backup heat; begin here if your heat pump is not providing enough heat or if your air conditioning system provides heat when it should be providing cooling.
* Blower Fan AUTO ON controls for air conditioning or heating blower fan units
* BLOWER FAN OPERATION & TESTING: problems with the blower fan on furnaces, heat pumps, and air conditioners
* COMPRESSOR CONDENSER: problems with air conditioner compressor/condenser units
* A/C - HEAT PUMP CONTROLS & SWITCHES: air conditioner controls and switches - begin here if your A/C won`t start. Here`s an important tip: most refrigeration problems, in air conditioners, refrigerators, or freezers, are electrical, not mechanical. In air conditioning school, we used to drive out and collect abandoned refrigerators that people were tossing out during our community`s spring cleanup week. Taking these appliances back into the shop we found that almost always the problem that had caused the owner to dispose of their air conditioner or freezer was in an electrical connection or electrical control. So it`s worth checking out switches and controls on an air conditioner before replacing more costly components.
* Dehumidification Problems - Air conditioner cools but does not dehumidify
* DUCT SYSTEM DEFECTS: problems with the air duct system, air filters, supply registers, return air registers
* ELECTRIC MOTOR DIAGNOSTIC GUIDE - troubleshooting an electric motor
* ENERGY SAVINGS in BUILDINGS - complete list of options to make buildings energy efficient
* EVAPORATIVE COOLING SYSTEMS - how can a "swamp cooler" or evaporative cooling system best deliver cool air in a building?
* Fire dampers, and Heating and Cooling Air Duct Controls such as manual and automatic duct dampers, zone dampers, and fire dampers are discussed and distinguished at DRAFT REGULATORS - barometric damper
* HEAT PUMPS - diagnosis & repair articles specifically for heat pumps
* LOST COOLING CAPACITY: what to do when not enough cool air comes out of the system
o What to check first if there is no cool air or not enough cool air
o Compressor failure diagnosis: checks of the air conditioner compressor
o Ducts & Air Handler diagnosis: basic checks of the indoor air handler (blower), air ducts, and filter system
o A/C Flow Too Weak - weak cool air flow can be caused by several problems, filters, icing, duct leaks, etc.
o A/C Filter Problems - dirty or missing filters cause other operating problems
o A/C Compressor Problems - quick check
o A/C Off - Condensate Pan Switch - some overflow pans have a switch that will shut down the system
o A/C Cooling Coil Icing - slow air flow, improper charge, etc. - eventually we get no cooling
o A/C Not Dehumidifying - improperly-sized unit, other causes, and cures for lack of dehumidification
o A/C Air Duct Problems - leaks, sizing, inadequate return capacity
o Air Conditioner Won`t Start - various causes including some simple switches to check
o Air Conditioner Refrigerant Problems - too much is as bad as too little; leaks, cures.
o Blower Fan No Start / No Stop - weird blower behavior can be diagnosed and fixed. See BLOWER FAN OPERATION & TESTING.
o Compressor Diagnosis: Diagnose & Repair - serious look into the compressor unit
o Cooling Capacity of the Duct System
* MANUALS & PARTS GUIDES - HVAC - where to find air conditioner, heat pump, and heating repair manuals, owners guides, installation guides, and parts lists
* OPERATING DEFECTS: major air conditioning problem symptoms and how to get the air conditioning system working again,e.g. compressor or fan noises, failure to start, and inadequate cool air volumes
* REFRIGERANT LEAK DETECTION: how to find and fix air conditioning refrigerant gas leaks. Also see REFRIGERANT LEAK DETECTION and REFRIGERANT LEAK REPAIR and REFRIGERANT PIPING & DISTANCES
* ZONE DAMPER CONTROLS . discusses manual and automatic air duct zone controls

HVA/C COMPONENT LIST - Air Conditioning & Heat Pump Components Inspection List - the basics
Photograph of older side-vent combination hot air furnace and central air conditioning system. The evaporator coil or A-coil is visible in the top of the unit.
Conventional cooling systems include the following components:

1. Indoor Components of an air conditioning system (Details can be read and seen at AIR CONDITIONER COMPONENT PARTS)
1. Air Handler Unit (AHU) which typically includes the following
* Air filters - located at return registers or possibly at or in the air handler
* Return Plenum
* Blower fan in a blower compartment
* Evaporator Coil = Cooling Coil
* Supply plenum
2. Supply air ducts and registers
3. Return air ducts and registers
4. Air filter(s) and possibly other air cleaning/IAQ equipment
5. Electrical shut off switches, circuit breakers/fuses

2. Outdoor Air Conditioning System Components (Details can be read and seen at AIR CONDITIONER COMPONENT PARTS)
1. Compressor motor - on residential units this is normally a hermetic motor-compressor combined in a single sealed unit
2. Condensing coil
3. Outdoor cooling fan
4. Electrical shut-off switch(es) for service & circuit protection

All of the components, controls, switches of air conditioning systems and how to diagnose and debug cooling system problems are discussed in detail at this website.

Photograph of commercial rooftop mounted A/C system Rooftop combined units: While the list above describes the common components of a typical residential air conditioning system, other configurations and packaged units are also in increased use in both residential and commercial installations.

Alternative air conditioning system designs may combine all components except for the duct work in a rooftop mounted unit such as the one shown above where it was mounted on a flat roof over offices at a commercial building.

Photograph of wall convector heating and cooling system Wall convector units (above) are often used for both heating and cooling in commercial installations and high-rise apartment buildings. The unit shown has its own compressor mounted right in the cabinet, visible at lower center in the photo.

Wall-mounted heating and cooling convector installations may be designed with one central heater or cooling system which feeds multiple units with chilled or heated water or possibly refrigerant from a single remote heating and cooling heat pump.

Another common residential alternative dispenses with duct work entirely, using a wall-mounted indoor evaporator/blower unit and a separate outside compressor/condenser. In this latter split design, one compressor/condenser may serve multiple wall-mount indoor units.
Photograph of this unusual attic air conditioning system is an example of the range of human creativity observed during a career of building inspections

Do-It-Yourself Home made air conditioning systems such as this goofy example may actually work but not without problems. This system used a window air conditioner placed in a home`s attic.

Manhole ventilation duct (liberated from New York City) was used along with a home made hood attached to the air conditioner to blow cool air into the home through a ceiling register. The air conditioning condensate was collected in the blue plastic kiddie pool seen in the photo, and drained by gravity to a plumbing vent stack.

Nothing about the system was proper, safe, nor very effective, and in addition, the attic moisture conditions were terrible as you can see from the blackened plywood roof sheathing.

RATED A/C or Heat Pump COOLING CAPACITY - How to Determine Air Conditioning Equipment Rated Cooling Capacity - the basics

How to estimate air conditioner size (C) Carson DunlopThe cooling capacity of an air conditioning system is expressed in BTU`s or tons. One ton of cooling capacity equals 12,000 BTU`s/hour of cooling capacity.

One ton" of cooling capacity, historically, referred to the cooling capacity of a ton of ice. Tons of ice does not explain a key ingredient in the comfort produced by air conditioning systems, dehumidification of indoor air - that is, taking water out of the air. Cool air can hold less water (in the form of water molecules or gaseous form of H2O) than warm air.

Think of the warmer air as having more space between the gas molecules for the water molecules to remain suspended.

When we cool the air, we in effect are squeezing the water molecules out of the air. When an air conditioner blows warm humid building air across an evaporator coil in the air handler unit, it is not only cooling the air, it`s squeezing out some of the water in that air. Both of these effects, cooler air and drier air, increase the comfort for building occupants.

There are several ways to determine the rated cooling capacity of an air conditioning system`s equipment. We discuss these in detail at COOLING CAPACITY, RATED.

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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
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 Accessibility
Air Filter Bypass Leakage
Air Filter Installation Procedure
Build Large Air Filters
Air Filter Location
Dirty Air Filter Problems
ENERGY SAVINGS by AIR FILTERS
Air Filtering Strategies
Missing or Leaky Air Filters
AIR FILTERS, OPTIMUM INDOOR
Air Filter Efficiency
Optimum Air Filter Design / Location
How to Cascade Air Filters
CONTINUOUS BLOWER FAN OPERATION
AIR FILTER EFFECTIVENESS
MERV, HEPA Definitions
MERV Air Filter Ratings
How Air Filters Work
Particle Sizes & IAQ
Gasketed air filters
Debris in Return Air Plenum
Washable air filters
AIR FILTERING STRATEGIES
FIBERGLASS & AIR FILTERS
Air Filters Shed Fibers?
Fiberglass & Test Lab Accuracy
Variations in Fiber Size
SOURCES FOR AIR FILTERS
OTHER AIR CLEANERS
AIR HANDLER / BLOWER UNITS
ADDING A/C: RETROFIT SIZING
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BLOWER LEAKS, RUST & MOLD
COOLING / EVAPORATOR COIL DEFECTS
DAMAGED COOLING COIL
DIRTY A/C BLOWERS
Leaks, Rodents In Air Handlers
Mold Growth in Air Handlers
DIRTY COOLING COIL
DIRTY COIL CLEANING PROCEDURES
FROST BUILD-UP on AIR CONDITIONER COILS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in BUILDINGS
ANIMAL ODORS IN BUILDINGS
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN BUILDINGS
BACKDRAFTING HEATING EQUIPMENT
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
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
CHINESE DRYWALL HAZARDS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS
COMPRESSOR & CONDENSING COIL, A/C
BURNED-OUT COMPRESSOR
CAPACITORS for HARD STARTING MOTORS
CONDENSING COIL FINS, SUPPORT PADS
HARD STARTING COMPRESSOR MOTORS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSTALLATION ERRORS, COMPRESSORS
MOTOR OVERLOAD RESET SWITCH
NOISY COMPRESSOR UNITS
PRESSURE READINGS, COMPRESSOR
REPLACING A COMPRESSOR
TIGHT or SEIZED AC COMPRESSORS
CONDENSATE HANDLING, A/C
DRIP TRAY DEFECTS
Missing Condensate Overflow Pan
Improper Condensate Drain Connects
Float Switch on Condensate Tray
Water in Condensate Overflow Pan
CONDENSATE LEAKS
CONDENSATE PUMPS
CONDENSATE DRAINS
Locations for Condensate Disposal
Plumbing Code for Condensate Drains
Improper Condensate Disposal
Condensate Drains Connected to Vent Pipe
Condensate Spills in Crawl Spaces
Condensate Leaks Onto Heat Exchangers
Condensate Disposal Outdoors
Condensate Drains to Hidden Location
CONDENSATE DRAIN CLEAN & DE-CLOG
CONDENSATE TRAY CLEANING
CONDENSATION or SWEATING PIPES, TANKS
CONDENSING COIL
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
FROM MODEL #
FROM EQUIPMENT RLA #
COOLING RULES OF THUMB
COOLING COIL or EVAPORATOR COIL
DAMAGED COOLING COIL
DIRTY COOLING COIL
DIRTY COIL CLEANING PROCEDURES
FROST BUILD-UP on AIR CONDITIONER COILS
DATA TAGS on AIR CONDITIONERS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
CONDENSING BOILERS/FURNACES
CONDENSING BOILERS/FURNACES DAMAGE
DEFINITION of Heating & Cooling Terms
Definition of BTUs, BTUH, & Calories
Definition of K value K-coefficient heat transmission
Definition of U value or U-coefficient heat loss resistance
Definition of R-Values for Insulation or Buildings
Definition of Design Temperature for Buildings
Definition of Heating or Cooling "Degree Day"
Definition of Tons of Cooling Capacity
DEHUMIDIFICATION PROBLEMS
CONDENSATION or SWEATING PIPES, TANKS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSE AIR CONDITIONER PROBLEMS
DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT SYSTEM & DUCT DEFECTS
ALLOY SYSTEMS FLEXDUCT
ASBESTOS HVAC DUCTS
BALANCING AIR DUCT FLOW
DUCT & AIR HANDLER ODORS
DUCT DAMAGE, MECHANICAL
DUCT INSULATION - Asbestos Paper
DUCT ROUTING & SUPPORT
DUCTS - Asbestos Transite Pipe
FIBERGLASS DUCT, RIGID CONSTRUCTION
FIBERGLASS HVAC DUCTS
FIRE DAMPERS in DUCTWORK
GOODMAN GRAY FLEXDUCT
INCREASING RETURN AIR
LEAKY DUCT CONNECTIONS
LOCATION OF REGISTERS & DUCTS
MOLD in AIR HANDLERS & DUCT WORK
ODORS in AIR HANDLERS & DUCT WORK
OWENS CORNING FLEXDUCT
OWL FLEXDUCT
RETURN AIR REGISTERS & DUCTS
SUPPLY DUCTS & REGISTERS
TRANSITE PIPE AIR DUCTS
UNDERSIZED RETURN DUCTS
UNSAFE DUCT OPENINGS
VIBRATION DAMPENERS
WATER & ICE IN DUCT WORK
WET CORRODED DUCT WORK
ZONE DAMPER CONTROLS
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ENERGY SAVINGS in BUILDINGS
AIR CHANGE RATE ACH HEAT SAVINGS
AIR LEAK SEALING PROCEDURE
ENERGY AUDIT - How to Use a Free One
ENERGY SAVINGS MAXIMIZE RETURNS ON
ENERGY SAVINGS PRIORITIES
ENERGY SAVINGS RETROFIT CASE STUDY
ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE
ENERGY SAVINGS RETROFIT OPTIONS
ENERGY USE MONITORING
HEATING COST SAVINGS METHODS
HOUSE DOCTOR, how-to be
TIMERS for ELECTRIC WATER HEATERS
VENTILATION, BALANCED HEAT COST SAVINGS
EVAPORATIVE COOLING SYSTEMS
FAN AUTO ON Thermostat Switch
FAN CONVECTOR HEATERS - HYDRONIC COILS
GAS MEASUREMENT TOOLS
Use of a Drager pump
How Colorimetric gas detection tubes work
Using the TIF 5000 Gas Detector
Warnings re instruments for detection of gases
Warning: choose the right tube for gas detection
HEAT LOSS (or GAIN) in BUILDINGS
How to measure heat movement through a wall
How to measure building insulation
How leaky is the building
BASEMENT HEAT LOSS
ENERGY AUDIT - How to Use a Free One
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEAT PUMPS
BACKUP HEAT for HEAT PUMPS
HEAT PUMPS, GROUNDWATER
HEAT PUMP STRATEGY - Indoors?
HEAT PUMP Thermostats - Outdoors
HEATING SMALL LOADS
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LEED GREEN BUILDING CERTIFICATION
LEED Building Designation & IAQ
LOST COOLING CAPACITY
What to Check First
A/C Flow Too Weak
A/C Filter Problems
A/C Compressor Problems
A/C Off - Condensate Pan Switch
A/C Cooling Coil Icing
A/C Not Dehumidifying
A/C Air Duct Problems
Air Conditioner Won`t Start
Air Conditioner Refrigerant Problems
Blower Fan No Start / No Stop
Compressor Diagnosis: Diagnose & Repair
Cooling Capacity of the Duct System
Repair Guide Master List
MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
ODORS in AIR HANDLERS & DUCT WORK
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
Air Conditioning System Temperatures
Instruments Used to Measure A/C Temperatures
Procedures for Making Temperature Measurements
PORTABLE ROOM AIR CONDITIONERS
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
REFRIGERANT LEAK DETECTION
REFRIGERANT LEAK REPAIR
REFRIGERANT PIPING & DISTANCES
RETROFIT SIZING for A/C or HEAT PUMPS
SOLAR ENERGY SYSTEMS
BLOCKBED RADIANT FLOORS - SOLAR DESIGN
GLASS vs HEAT MIRROR SOLAR GAIN/Loss
GREENHOUSE DESIGN for SOLAR HEATING
GREENHOUSE / SUNSPACE GLARE
PASSIVE SOLAR DESIGN HANDBOOK - PDF
PASSIVE SOLAR DESIGN KEY ELEMENTS
PASSIVE SOLAR DESIGN METHOD
PASSIVE SOLAR ENERGY MONITORING
PASSIVE SOLAR FLOOR TILES, PHASE CHANGE
PASSIVE SOLAR HEAT PERFORMANCE
PASSIVE SOLAR HOME, LOW COST
PASSIVE SOLAR PERFORMANCE PROBE
PASSIVE SOLAR Roof & Window Overhangs
PHOTOVOLTAIC POWER SYSTEMS
POLYCARBONATE GLAZING
REMOTE ELECTRIC POWER, PHOTOVOLTAIC
ROCK-BED SOLAR HEAT STORAGE DESIGN
SLAB INSULATION, PASSIVE SOLAR
SLATE THERMAL MASS for SOLAR HEAT STORAGE
SOLAR COLLECTOR AIR or GAS COLLECTION
SOLAR COLLECTOR EFFICIENCY COMPARISONS
SOLAR COLLECTOR FILMS
SOLAR COLLECTOR OUTGASSING
SOLAR COLLECTOR WOOD HOUSINGS
SOLAR GAIN CALCULATION
SOLAR HEATING SYSTEM DESIGNS
SOLAR HOT WATER HEATERS
SOLAR HOUSE EVALUATION
SOLAR MODULE MANUFACTURERS
SOLAR SHADES & SUNSCREENS
SOLAR SHADES, LOW-E EFFECTIVENESS
SOLAR WATER DISINFECTION
SUNSPACE DESIGN for SOLAR HEATING
SUNSPACE GLAZING for SUNTANNING
STORM WINDOW INTERIOR
STORM WINDOW PLASTIC CHOICES
STORM WINDOW WEEP HOLES
SUNGAIN, FILMS, LOW-E GLASS
SUNSPACE GLAZING for SUNTANNING
SWIMMING POOL SOLAR HEAT, INDOOR
SWIMMING POOL SOLAR HEAT, OUTDOOR DIAGNOSIS
THERMAL MASS in BUILDINGS
SEER RATINGS & OTHER DEFINITIONS
SEER RATING HISTORY
SYSTEM OPERATION
OPERATING CONTROLS
SAFETY CONTROLS
THERMOSTATS
Types of Building & Room Thermostats
How Thermostats Work
Detailed Guide to Room Thermostats
How to Set the Thermostat
COOL OFF HEAT Thermostat Switch
FAN ON AUTO Thermostat Switch
HEAT ANTICIPATOR Adjustment
HEAT ANTICIPATOR Mini Ammeter to Check
HEAT PUMP Thermostats - Outdoors
INSTALL & WIRE Thermostats
TEMPERATURE RESPONSE of Room Thermostats
SWITCH FUNCTIONS on a Room Thermostat
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS on A/C SYSTEMS

* 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 Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
* 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.).
* Thanks to Scott at SJM Inspect for suggesting this EPA document and for technical editing remarks regarding our air conditioning website, SJM Inspection Service LLC, serves the entire state of CT, sjminspect.com 203-543-0447 or 203-877-4774 5/16/07
* This website discusses these air conditioning and heat pump terms and problems: Air Conditioners: Central Air Conditioning Troubleshooting & Repair Guide: How to Inspect, Diagnose, & Repair Central Air Conditioning: Defects in A/C compressors, air handlers, duct work, and controls. We explain how to inspect & repair central air conditioning systems and for homeowners we also answer basic HVAC questions such as what are the basic air conditioning components? We provide guidance in determining air conditioning cooling capacity & energy efficiency, Troubleshooting air conditioning compressor problems, Diagnosing air conditioning air handler problems, Air conditioning condensate problems, Duct system inspections, defects, repairs, Cleaning air conditioning equipment & A/C refrigerants.
* HVAC brands discussed include but are not limited to: Lennox, American Standard, Amana, Everrest, Goodman, Frigidaire, Coleman and Gibson. Brands of related air handling equipment include Honeywell, Aprilaire, White-Rogers, Broan. Nutone, Fantech, Venmar, Arzel, Hi-Velocity, Vanguard, Wirsbo, Weil McLain, Unico, Heat Link, A.O. Smith, Water Furnace, ClimateMaster, Geo-Excel, Command Aire, Friedrich, LG, Mitsubishi, Sanyo, Hart &
Cooley, Munchkin, Superstor Ultra, Lochinvar and Knight HVAC equipment.

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.
* Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.

* Home Reference Book - Carson Dunlop The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of 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.

* Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
* Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
* "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]
* Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
* 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.).
* Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
* NewAir Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
* Asbestos HVAC Ducts and Flues field identification photos and guide
* Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
* Ratib Bakera is member of Refrigeration Service Engineers Society (RSES), an International training organization for the HVACR industry provides educational and certification programs to HVACR professionals of all experience levels. www.rses.org provides information on the organization and its training materials. Independent testing and certification of HVAC technicians is provided by North American Technician Excellence - NATE - see www.natex.org. NATE is supported by ASHRAE, the US EPA, and a host of other trade and professional associations.
* Singer brand HVAC equipment brand history: Singer was bought by & became the climate control unit of Dallas-based Snyder General Corp. (founded by a former Singer HVAC manager) in 1982. The name Singer was dropped in 1984. In 1984 Snyder General operations included Arcoaire, Comfortmaker, and McQuay. In 1991 Snyder General sold Arcoaire & Comfortmaker to Inter-City Products. In 1994 Snyder General was acquired by Hong Leong Group Malaysia. Snyder General is at 2001 Ross Avenue Dallas, TX 75201.
* Lennox air conditioning and heat pump owners manuals for air conditioners, air handlers, furnaces, heat pumps, indoor air quality systems, packaged units, water heaters, zone controls and other controls such as thermostats, are provided by Lennox at http://www.lennox.com/support/manuals.asp
What to Check First if the Air Conditioner Output is Inadequate or A/C Won`t Run
These Simple Checks May Enable Inexpensive Repair of Lost Cooling Output from an Air Conditioner

Before ordering an expensive air conditioner service call to restore lost cooling capacity, here are a few simple steps to perform. Some of these can be done by any homeowner, others may require a bit more expertise. Below we provide first a very basic Air Conditioning or Heat Pump Diagnostic Checklist, followed by more detailed descriptions of common problem cooling system topics.

First try our air conditioner checklist just below - try these steps before calling your HVAC service company.

Following the checklist we provide more detailed descriptions, photos, and links to in-depth air conditioning inspection, diagnosis, and repair or improvement advice.
Air Conditioning Checklist for Lost Cooling: What to Do First
If the air conditioning system is not running at all:
Air conditioning thermostat (C) Daniel Friedman

1. Check the Room Thermostat Temperature Setting: Set the thermostat to at least 5 degrees below room temperature. Our elderly mom has no patience with switches and controls. She regularly calls her air conditioning service company with a service request, sometimes late at night, because she has simply failed to set the temperature on the thermostat lower than the room temperature. Don`t drive your A/C like our mother.
2. Check that the Room Thermostat is set to "Cool" not "Off" or "Heat". If the thermostat is not set to "cool" it is simply turning off your A/C.
3. Check that electricity is on for the equipment. Check all switches and controls, including service switches, including outside by the compressor, inside at the air handler, and fuses or circuit breakers in the electrical panel.

For example, condensate spilling into an overflow pan that uses a sensor switch can be enough to shut down your air conditioner. There are several switches and controls, both manual and automatic that can leave an air conditioner or heat pump turned "off" such as a blower compartment door interlock safety switch, an electric motor overload or overheat switches, and a condensate tray spillage detector switch.

Watch out: See A/C - HEAT PUMP CONTROLS & SWITCHES to be sure you have found and checked every manual or automatic electrical switch on the system. A bad or failed starter capacitor could also be leaving your system shut down, failing to start a blower, fan, or compressor motor.

If the air conditioning system is still not working, or if the A/C system is running but cool air is not coming out of the supply registers you probably need to call a service technician, but below are some things to check further yourself.
If At Least Some of the Air Conditioner or Heat Pump Equipment is Running but Cool Air is Not Being Delivered:

If the air conditioning system is still not working, or if the A/C system is running but cool air is not coming out of the supply registers you probably need to call a service technician, but here are some things to check further yourself. Just after these checks we discuss what to do if the air conditioner is running but air flow is too weak (A/C Flow Too Weak) or too warm.

1. Check the Outside Air Conditioning Compressor: is the outdoor compressor-fan unit (COMPRESSOR & CONDENSING COIL) running? If not, be sure that the outdoor service switch and the indoor power switch, fuse, or circuit breaker are all in the "on" position. Check the outside compressor condensing coil for damage or blockage. A blocked condensing coil can cause the compressor to overheat, stop running, or become noisy and work poorly. A/C Compressor Problems
2. Check the Indoor Air Handler: is the indoor blower unit running? If not be sure that the electrical power switch at your furnace or air conditioner air-handler is in the "on" position. Sometimes there is more than one switch, such as one right at the unit and another at the entry to the room where the equipment is located, or even upstairs on a higher floor if your air handler is in a basement or crawl space. Make sure that the blower compartment cover or door is properly closed or an interlock switch may be keeping the system "off". Also remember to check for a dirty, blocked COOLING COIL or EVAPORATOR COIL. A coil blocked by ice or dirt will not produce cool air. A/C Cooling Coil Icing.
3. Check the air filter(s): if your air conditioning equipment is running but little or no cool air is coming out of the supply registers, check that your air filter(s) have not become blocked with dirt and debris. Usually the air filter is right at the air handler or blower unit, or your air filter may be installed behind a grille covering a central warm-air return that sends air back to the air handler. See A/C Filter Problems
4. Check the air supply registers: in ceilings, walls, or floors, where cool air is supposed to be delivered to various rooms in the building, be sure that the register is in the "open" position (you will be able to see through it into the ductwork) and be sure you haven`t blocked the supply registers with a carpet or furniture. Remember that a duct may have become disconnected in an attic or crawl space.
5. Check the blower fan assembly: if the blower fan itself won`t start, see BLOWER FAN OPERATION & TESTING. Also see ELECTRIC MOTOR DIAGNOSTIC GUIDE.

How to Diagnose Air Conditioner Output Cool Air Flow Too Weak, Too Cold, or Too Warm
AC duct and air handler temperature measurement points (C) Carson Dunlop

Air Conditioner Blower fan unit not moving enough air: too little air coming out of your air conditioning ducts?

Check the condition of the blower unit: if it`s dirty the blower may be spinning but not moving much air. See DIRTY A/C BLOWERS for details.

Dirty filters or iced coils or crimped or disconnected air ducts can also cause loss of cool air or too little cool air coming out of supply registers.

These items are addressed below in this air conditioner diagnostic guide. Also see DIRTY COOLING COIL and FROST BUILD-UP on AIR CONDITIONER COILS.

Sketch courtesy of Carson Dunlop

Air flow that is too slow for any reason (such as a dirty filter or dirty blower fan assembly blades) can cause first, air temperatures that are abnormally low coming out of the air conditioner, and eventually a reduction in air flow as coil ices over. See A/C Cooling Coil Icing.

Air flow that is too fast for any reason (improper fan motor, speed, fan belt or pulley size, duct design, duct registers removed, etc) can produce air that is not cool enough and can prevent proper air dehumidification (oversized A/C system). A/C Not Dehumidifying.
Check and Fix Existing Air Conditioning Problems Before Trying to Improve its Cooling Capacity

Watch out: It could be a mistake to spend on any costly air conditioning improvement if the original system actually already had the needed capacity, but simply needed maintenance (like replacing a filter - A/C Filter Problems) or repair (like repairing a leaky duct - A/C Air Duct Problems).

FIRST: review all of the air conditioning performance diagnosis suggestions here at - LOST COOLING CAPACITY to be sure there is not something that needs to be repaired or corrected with the system. For example we have seen cool air output significantly improved by finding and fixing a disconnected cool air duct that no one had noticed in a hard-to-access crawl area.

Certainly some central air conditioning systems, especially retrofit designs, have less than optimum duct design, such as inadequate central return air registers, room doors that are so tight that it is difficult to blow cool air into the room when the door is closed, inadequate supply ducts or less than optimum supply register placement such as only in floors. But redesigning and installing for an optimum air conditioning duct system can be costly, so it might be worth taking some other steps.

SECOND: make sure that other energy-savings steps have been taken in the building, such as proper insulation, sealing un-wanted drafts, etc. See ENERGY SAVINGS in BUILDINGS - those suggestions apply to both heating and cooling costs.

If your HVAC service technician is sure that the present cooling system is working as intended, then if you are not considering supply or return air duct improvements, or a replacement air conditioner system of higher capacity, you might consider a stronger blower fan (discuss what you could do with your HVAC tech), or booster fans individual registers.

Watch out - just boosting air conditioner air flow by installing a higher capacity blower fan is not that simple - if the blower moves air through the duct system faster than the design speed for the system ,the cooling coil may be insufficient in capacity, the air will not be dehumidified (and the building will be less comfortable - A/C Not Dehumidifying), or you might get annoying duct or equipment noises. Discuss these possibilities with your HVAC service company.
Air Conditioner Filter Clogging Problems Cause Weak Cool Air Flow
Dirty filter blocks air flow (C) Daniel Friedman

Clogged Air Conditioner filters can lead to lost cooling capacity first, because the clogged filter reduces the air flow through the system, meaning that you`ll feel less air flow at the supply registers than was previously present.

See AIR FILTERS for HVAC SYSTEMS for details.

Air Filter problems: not enough air coming out of air conditioning ducts? Check for a very dirty, blocked air filter or blower fan. See AIR FILTERS for HVAC SYSTEMS and AIR HANDLER / BLOWER UNITS
Air Conditioner Compressor Problems - noisy or hard starting air conditioner compressors
Air conditioner compressor condenser unit (C) Daniel Friedman

Compressor problems - Air Conditioner Compressor: problems such as an aging air conditioner compressor motor that is at or near the end of its life may be unable to properly compress the returning refrigerant gas to a sufficiently high pressure. A service technician will need to evaluate and test the system and if needed, replace the compressor.

Since this is a costly repair, be sure to ask why the compressor failed and to correct any underlying cause (such as low voltage). Variations in line voltage can lead to improper compressor operation and loss of cooling output.

If you have a hard-starting air conditioner compressor that "hums" but doesn`t start, it may be possible to get more life out of the compressor motor with a simple starting capacitor (rather than a costly whole new compressor motor.) See and HARD STARTING COMPRESSOR MOTORS and CAPACITORS for HARD STARTING MOTORS.

We first mentioned at NOISY COMPRESSOR UNITS that we had a field report from a reader who explained that a noisy outdoor compressor unit was, according to his HVAC service technician, traced to a blocked, clogged outdoor condensing coil. We speculate that perhaps the compressor was running hot and that correcting air flow across the condensing coil corrected that condition.

Air conditioner compressor problems, including compressor noises, hard starting, and burned-out compressors, are explained in detail beginning at COMPRESSOR & CONDENSING COIL and includes topics such as BURNED-OUT COMPRESSOR and MOTOR OVERLOAD RESET SWITCH.
COMPRESSOR/CONDENSER COOLING - Can Cooling Down the Air Conditioner Compressor Motor to Keep the A/C Working?

Several readers have described a step of cooling down an overheated air conditioning or heat pump compressor motor to get it running again producing cool air indoors. One reader used a garden hose to spray the outdoor unit (after all it`s intended to tolerate being rained-on). Another used a watering can. A third, buckets of water.

All three reported that this step got their cooling system cooling again when before either the compressor had stopped running entirely or it was running but the system was not producing cool air. But for several reasons this is not an effective durable repair:

* The "repair" achieved by pouring water over a hot compressor is not lasting and if you wet electrical components it could cause damage or be dangerous
* It`s hot standing outside dumping water on your A/C unit and you`re not supposed to have to do that
* The loss of cooling means there is some problem to be found and fixed

While we wait for more comments from air conditioning service technicians and experts (CONTACT us), here are some interpretations of what may be going on:

1. The A/C compressor motor may be at or near end of life, running hot. An air conditioner motor that is overheating may turn itself off on thermal reset. In this case when the motor cools down it may automatically reset itself and start up again - for a while. Sometimes you can get a compressor motor starting again on its own by adding or replacing a starting capacitor - see CAPACITORS for HARD STARTING MOTORS. Also see MOTOR OVERLOAD RESET SWITCH. Also see HARD STARTING COMPRESSOR MOTORS.
2. The A/C compressor motor may be overheating due to its location: for example in hot sun. Most equipment will tolerate this condition but an older unit or very hot sunny conditions may lead to thermal overheating and an overload circuit trip-off.
3. The A/C system compressor/condenser fan may not be running or may be damaged, failing to adequately cool the refrigerant gas in the condensing coils. Watch the fan to see that it is running while the compressor motor is on, and perhaps even before and after the compressor motor starts or stops. [But not indefinitely.]
4. The A/C condenser unit coils may be blocked, bent, dirty, damaged. It may be possible to clean the coils of leaves, dirt, grass kicked up by nearby mowing, etc. and thus improve the condenser operation and start making cool air again. COMPRESSOR & CONDENSING COIL
5. The air conditioning or heat pump system may be very low on refrigerant. You`ll need a service technician to check and repair this condition. REFRIGERANT LEAK DETECTION

Air Conditioner Cooling Coil Icing Problems & Coil Leaks
Ice blocked air conditioning cooling coil (C) Daniel Friedman

Cooling Coil Ice-Up on the air conditioner air handler or evaporator coil: A second result of the reduced air flow due to a dirty air conditioning filter can cause the evaporator coil (the cooling coil) in the air handler to become blocked by ice, stopping or significantly reducing cool air output from the system.

A visual inspection of the cooling coil in the air handler can quickly show whether or not it`s ice-covered. If the coil is iced-up and blocked, turn off the cooling system entirely until the ice has all evaporated and cleared. Be sure that your condensate drain is not blocked and that the water from melting ice will be properly disposed-of.

If you replace all dirty filters on the system and remove ice from an iced coil and the coil ices up again when the system is turned back on, you may have the next condition in this list.

For a detailed discussion of air conditioner or other refrigeration (or dehumidifier) cooling coil ice-up diagnosis and cure, see Air Conditioning Cooling Coil or Evaporator Coil Ice-up at FROST BUILD-UP on AIR CONDITIONER COILS

Cooling Coil (Evaporator Coil) Leaks, Condensing Coil Leaks: if your A/C system used to work fine but now is blowing only warm air, it is possible that you have lost refrigerant in the system. A refrigerant leak can occur anywhere in the refrigerant piping system, in the cooling coil, or in the condensing coil.

You`ll need an HVAC technician to find and repair the leak problem. If the leak is in a refrigerant line it can usually be soldered and sealed and the system re-charged. If the leak is in a cooling coil or condensing coil, the coil probably needs to be replaced. We explain this topic in more detail below at Air Conditioner Refrigerant Problems - Refrigerant Leaks, Low Refrigerant, Wrong Temperatures.

Also see REFRIGERANT LEAK DETECTION and REFRIGERANT LEAK REPAIR.
Air Conditioning System Dehumidification Problem Diagnosis & Cures
Sketch explaining that oversized air conditioners are a mistake (C) Carson Dunlop

Air Conditioning Dehumidification Problems: air conditioning system cools but does not dehumidify the room. The most common cause of inadequate dehumidification by an air conditioning system is the installation of a cooling unit which has too much capacity, or is "over-sized" for the space it is being used to cool. What happens is simple:

If an air conditioning compressor unit is oversized (too many BTUH of cooling capacity) what happens is it cools the room so quickly that the system does not move enough total volume of air across the cooling coil to remove much moisture before the room temperature has dropped to the A/C cut-off point.

In other words, an air conditioner needs to run longer, and move more total volume of air through itself to drop room humidity than it does to just cool the air. So "bigger" cooling capacity or higher BTU capacity for an air conditioning system is not necessarily better, and it can actually be a problem.

Key Air Conditioning Inadequate Dehumidification Symptom: If your cooling system is otherwise working normally, and it cools the room temperature quickly but the room humidity stays high, an over-sized unit is likely to be the problem.
Cures for inadequate dehumidification by an air conditioner

Air conditioner that was not dehumidifying (C) Daniel Friedman

* First make sure that the equipment is operating properly: is it cooling - check that temperatures are dropping normally when the system is running.
* Check that there is not an abnormal moisture source such as leaks into the building or its wall or ceiling cavities from any other source. Check to see if the condensate drain from the air conditioner is producing water.

If you see lots of A/C condensate dripping out of the system condensate drain but room humidity is still high, we suspect that there may be an abnormal humidity source. At the end of this list we discuss adding additional dehumidification capacity.
* Adjust the A/C unit controls to increase dehumidification: discuss with your HVAC service technician whether there are technical changes that might be made to fan speed or other controls that might improve A/C unit dehumidification. We`re doubtful there is much mileage in this but it`s worth asking.
* Increase the cooling load on the installed air conditioner by making it cool a larger area - like maybe leaving the doors open to other rooms - which we doubt is suitable in most cases. Our photo (above left) shows a wall mounted air handler from a Sanyo™ split system air conditioner that was not adequately dehumidifying the bedroom where it was installed, even though the room was cold enough to hang meat.

The occupants experimented with leaving the bedroom door opened, as the rest of their home did not have air conditioning. That proved just enough to cause the system to dehumidify beautifully.
* Adjust the building HVAC system ductwork: if a non-dehumidfying central air conditioning system (as opposed to a window unit or a wall-mounted split system unit) is otherwise working well, it may be possible to adjust its load and thus improve its dehumidification by making changes in the duct system, such as increasing the return air to the air handler from additional building areas.
* Replace the oversized air conditioner: Unfortunately the most likely fix for an A/C system that is not dehumidifying may be an ugly one - either replace the unit with one that is properly matched to the size of the area to be cooled
* Select an A/C unit of the proper size. See AIR CONDITIONER BTU CHART for the data useful to do this. Whoever selected and installed the air conditioning unit needed to relate the room size to the AC capacity. Also see COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs and see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment.
* Add supplemental dehumidification. For wet conditions that exceed the capacity of the air conditioner itself, or when you require both unusually low temperatures and further dehumidification (such as a seed storage facility described by one of our readers), it may be necessary to add a separate free-standing or portable dehumidifier to the system to reach the temperature and humidity targets you need.

In an area of our forensic laboratory we use a Sears® dehumidifier, model 580.54501 - 50 pint (also available as 580.54701 - 70 Pint Low Temp) (cost about $200.). The Sears portable dehumidifier instruction manual (Part# 3828A20803B) confirms on p.7 that the humidity control can be set anywhere between 35% and 70%. You can also adjust the fan speed (low / high) and also set an on-off cycle period of 3 hrs or 6 hrs.

Operating a dehumidifier (which uses the same technology as an air conditioner) will have a side effect of pumping a little heat into the dehumidified area - the output side of the dehumidifier produces air that is warmer than its input side. Depending on the size of the area being conditioned, that added heat might help compensate for an air conditioner that was a little oversized for the space.

Air Conditioning Air Duct Problems and Cool Air Flow Defects - Poor Air Flow

Crimped cooling duct (C) Daniel Friedman

* Duct problems: Damaged Air Conditioning Ducts such as ducts which have been improperly routed and are crimped, crushed, or have excessive bends can reduce cool air flow in an otherwise properly functioning system.

One client had us drive a considerable distance to repair her apartment`s central air conditioning system after having had several unsuccessful service calls.

Apparently no one had managed to get into a rather tight and hard-to-enter attic crawl space where the cooling ducts were routed. We found that the main cooling duct had become disconnected.

The attic was nice and cool but no cool air was being blown into the living area. Check the condition of the duct system for blocked ducts, loose leaky connections, closed dampers, crimps and bends, before calling your service technician.

See DUCT SYSTEM DEFECTS for details of various A/C supply and return air duct and register problems and how to detect and correct them.

Air Conditioner Won`t Start - electrical problems

As we stated earlier, check that electricity is on for the equipment, everywhere. Check all switches and controls, including service switches, including outside by the compressor, inside at the air handler, and fuses or circuit breakers in the electrical panel.

For example, condensate spilling into an overflow pan that uses a sensor switch can be enough to shut down your air conditioner. There are several switches and controls, both manual and automatic that can leave an air conditioner or heat pump turned "off" such as a blower compartment door interlock safety switch, an electric motor overload or overheat switches, and a condensate tray spillage detector switch. See A/C - HEAT PUMP CONTROLS & SWITCHES to be sure you have found and checked every manual or automatic electrical switch on the system. A bad or failed starter capacitor could also be leaving your system shut down, failing to start a blower, fan, or compressor motor.
Damaged air conditioner electrical wire (C) D Friedman T Hemm

Electrical problems: air conditioning system won`t start: it may sound silly, but is the air conditioner turned on?

Has the cooling thermostat been set to "cool" and the temperature set below ambient room temperature?

Do both the outdoor compressor/condenser unit and the indoor blower fan/evaporator coil unit have electrical power?

Has the air conditioning electrical wiring been physically damaged or cut? Photo courtesy of Tim Hemm.

Are the power switches on at these units, are the fuses good, are the circuit breakers in the "on" position, and is the thermostat set correctly? See A/C - HEAT PUMP CONTROLS & SWITCHES and THERMOSTATS for some diagnostic tips.

Air conditioner compressor problems, including compressor noises, hard starting, and burned-out compressors, are explained in detail beginning at COMPRESSOR & CONDENSING COIL and including topics such as BURNED-OUT COMPRESSOR and HARD STARTING COMPRESSOR MOTORS and MOTOR OVERLOAD RESET SWITCH and ELECTRIC MOTOR DIAGNOSTIC GUIDE.
Air Conditioner Won`t Start or Stays Off Due to Condensate Pan Switch
Condensate tray lockout switch (C) Daniel Friedman

Condensate pan switch lockout: an attic or other air conditioner air handler condensate drip tray or drip pan located under an air handler is installed to catch air handler condensate leaks if the normal condensate drain system fails. Some condensate pans have their own separate overflow drain (a proper installation) or share their drain with the normal condensate drain (an improper installation).

But on some air conditioning air handlers the installer may provide a condensate overflow pan switch rather than a separate pan drain line. In this installation the switch is designed to turn off the air conditioning system if it finds condensate water in the overflow pan. The idea is to shut down the air conditioner before there is a more costly leak into the building insulation or ceiling.

Condensate leaks into the condensate pan can shut down the air conditioner.

In tracking down an air conditioner condensate leak, I found that the the condensate pump drain line, a small-diameter PVC pipe, was clogged with water mold. That was why my air conditioner wasn`t kicking on. It would of ended up costing at least a hundred dollars just for a service tech to fix something as simple as that. I had to take the pump apart and clean it. I took off the PVC drain line coming out of inside air conditioner and blow and clean it all out too. - Jacob Behrends, FL

So if your air conditioning system seems to be normal in all other respects but it simply won`t turn on, check for a flooded condensate pan or a defective condensate switch. See DRIP TRAY DEFECTS and also Use of float sw



More Information: Original article