 Complete List of All Air Conditioning & Heat Pump System Controls & Switches
|
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
HVAC system controls & switches: this article explains where to find and how to use the switches and controls for air conditioning and heat pump systems. We list and explain the function of each air conditioner or heat pump control or switch, including providing identification photographs and troubleshooting tips. HVAC control definitions & photos are organized by where they are found: indoors or outside of the building, and at the air handler/blower assembly or the outdoor compressor/condenser unit, or perhaps in other locations such as wall thermostats or electrical panel main switches.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Air Conditioning & Heat Pump CONTROLS & SWITCHES
We include photographs to assist readers in
recognizing cooling system defects. Other articles at this website discuss certain of these controls in greater detail. See SYSTEM OPERATION for a discussion of thermostats, zone dampers, and circuit breakers on air conditioners and heat pumps. Also see THERMOSTATS and THERMOSTATIC EXPANSION VALVES.
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 add HVAC system switches or controls or diagnostic suggestions you do not find here.
Detailed List of Air Conditioning & Heat Pump Parts, Switches and Controls
Here we list all of the controls and switches on a typical split system air conditioner with indoor and outdoor components include the items listed just below.
If the A/C system won't operate, before requesting a service call check that it is turned on at every control, switch, or circuit breaker,
and that the thermostat is properly set.
A/C - HEAT PUMP CONTROLS & SWITCHES
Outside Switches, Fuses, Breakers
Inside Switches,Components
Air Handler / Blower Switches
Blower Door Switches
Backup Heat Controls
CAPILLARY TUBES
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Compressor Condenser Switches, Controls
Condensate Overflow Switch
CONTACTOR RELAY DIAGNOSIS & REPAIR
Duct System Switches
Duct System Filters
OPERATING CONTROLS, A/C & HEAT PUMP
Starter Capacitors
Thermostats & Controls
Thermostatic Expansion Valves
Motor Overload / Overheat Reset Switch
Pressure Controls & Safety Switches
Zone Damper Controls
The main operating controls for HVAC systems and their functions are are discussed at SYSTEM OPERATION where you will find a discussion of thermostats, zone dampers, and circuit breakers on air conditioners and heat pump systems.
We explain these many electrical switches and controls that control an air conditioner or heat pump system. You'll need to check these first if your air conditioner won't start or won't keep running. Other air conditioning and heat pump diagnostic procedures are at LOST COOLING CAPACITY.
If the A/C or heat pump system will not run check all of these control and safety switches listed here before calling your service technician. If someone or some condition has
turned one of these switches off, resetting it may be all that's needed. Not all of these switches will be present on every system; fuses may be used instead of circuit breakers; fuse pullouts
may be used instead of a circuit breaker or fuse at some service switches.
Watch out: Safety warning: do not put your fingers or hands inside of a heating furnace or air conditioner blower or blower compartment without
making certain that all electrical power to the unit has been shut off. If the blower starts turning you can lose a finger, and there are also
electrical shock hazards in these areas.
Key Air Conditioner or Heat Pump Main Electrical Control Switches, Fuses, or Circuit Breakers
- Air handler circuit breaker: in the electric panel there will be a switch controlling power to the air handler/blower circuit, perhaps
two different circuits, one for the air handler unit, and a second for the compressor/condenser unit (the next item listed below) - also see CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
- A/C or Heat Pump Compressor circuit breaker: in the electric panel there will be a switch, circuit breaker or fuse controlling power to the outdoor compressor circuit - also see CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
- A/C indoor Air handler service switch: usually indoors at or right on the indoor air handler/blower unit, this switch is normally always "on" except during equipment servicing.
- A/C outdoor compressor/condenser unit service switch typically on the unit or on a building wall surface close to it. This switch is normally always "on" except during equipment servicing. Also see Outside Switches, Fuses, Breakers
- Air conditioner or heat pump thermostat: one or more indoor wall mounted thermostats must be set properly to call for cooling (or heating). Split system air conditioners and heat pumps may use a remote control device to turn the equipment on or off and to set the desired temperature. See THERMOSTATS.
- Other electrical switches and controls such as an air conditioner or heat pump pressure safety switch found on or near the compressor/condenser unit and in some window and through-wall units can also shut down an air conditioner or heat pump system, as we discuss below in this article.
- Electrical panel circuit breakers or fuses will be provided separately to control the air handler (blower system) circuit and
the compressor/condenser circuit. Of these the compressor is usually supplied by a 240V circuit and the air handler by a 120V circuit.
- Compressor safety shut off switch outside at the compressor/condenser. The switch may be a circuit breaker, fuse, or a simple "pull-out"
disconnect located close to the compressor.
- Air handler service switch inside on or close to the air handler unit itself
- Air handler blower compartment safety switch: a safety interlock that will turn off electricity to the air handler or blower unit if the blower compartment door is not securely shut. If your air conditioner blower will not start this switch and the blower compartment doors should be checked. See BLOWER FAN OPERATION & TESTING
- Air conditioner/heat pump contactor relay switch: turns on high amp drawing equipment such as the compressor motor. See CONTACTOR RELAY DIAGNOSIS & REPAIR
- Air conditioner or heat pump pressure control & pressure safety switches: turns off the system at excessive refrigerant pressure and in some systems at too-low pressure. Also used in automotive air conditioning. See Pressure Controls & Safety Switches
List of Outside A/C or Heat Pump Service Switches, Fuses, Circuit Breakers
The pair of photographs just above show the outdoor air conditioner or heat pump compressor/condenser service control switch, in this case a circuit breaker, installed outside at a compressor
for a ductless cooling system compressor.
More photographs of a ductless or split system air conditioning system are at A/C TYPES, ENERGY SOURCES.
Our page top photograph is an important one to study further. The air conditioning system compressor/condenser service switch for this
outdoor unit was a 240V fused circuit with outdoor fuses in the box shown in the photo. In
this close up photograph you can just make out that someone has installed
1/2" copper pipes in place of the original fuses.
This might be a dangerous installation, risking fire as well as a burn up of the air conditioning equipment. But as Mark Cramer pointed out, if the circuit were properly protected by breakers or fuses at the main panel, the insertion of metal pipes
in these fuse sockets just converts the device from a fuse box to a simple switch.
In any case, simply installing fuses would restore the proper
safety device but it's likely that further testing and diagnosis of the electrical circuit and the compressor/condenser unit will
be needed to determine why someone installed copper pipes where fuses belonged in the first place.
When someone converts fuses to a switch in this location it may be because the air conditioning system was frequently blowing the fuses --
someone wanted to force the compressor/condenser to run.
Compressor Condenser Controls & Switches
Circuit breaker(s) at the electrical panel
protect the circuit supplying power to the air conditioning system. Typically separate circuit breakers (or fuses) power the compressor/condenser unit and the indoor air handler/blower assembly.
Watch out: your HVAC equipment may be run out of a sub-panel rather than the main electrical panel. Be sure you have found all of the electrical panels, sub panels, and manual control switches for the equipment both inside the building and outdoors.
Watch out: really watch out: if you re-set a circuit breaker or replace a fuse and the breaker trips again or the fuse blows again, leave the equipment off and call a qualified service technician. You probably have an unsafe condition. Forcing electrical equipment to run can cause shock or fire.
Compressor/Condenser Unit: the "outside" portion of an air conditioner or heat pump, the compressor re-compresses refrigerant gas back into a liquid and in the process, moves heat (in the refrigerant) either from indoors to outside (air conditioning mode) or from outdoors to inside (heat pump mode) if the system is a heat pump.
See COMPRESSOR CONDENSER for details of the diagnosis and repair of compressor problems.
|
|
Compressor service switch:  The air conditioning system compressor service switch is located outdoors, at the compressor/condenser unit, typically on a building wall near the outdoor unit,
this switch may be a circuit breaker, a fuse block pull-out, or a simple electrical switch.
Service switches permit a service
technician to work safely on the equipment by turning off electrical power to the unit without having to run back and forth
through the building to the main electrical panel. Where the compressor/condenser service switch is omitted some technicians are tempted to work on
equipment while it is electrically "live", and a few of them get shocked. These switches are required by current electrical
codes but may be absent on old A/C installations.
If no service switch is installed at the compressor/condenser you should have
one installed at the next A/C service call or next electrical work done on the building.
In our photograph the A/C service
switch is very unsafe for two reasons: first, because it is falling off of the wall it may be difficult to operate the switch.
Second, ask yourself, "What happened to the screws that were used to fasten this switch to the building wall?" We've seen cases
of the mounting screws falling into the switch box, causing a short circuit or even a fire. In this particular case
the vinyl siding installers pulled the switch loose to install siding and didn't bother to reinstall it.
|
Air Conditioner/Heat Pump Contactor Relay Switch
|
A/C and heat pump systems use a contactor relay (circled at left) because the little 12-24V wall thermostat circuit and switches are not capable of handling the higher voltage used by the compressor/condenser motors.
The contactor relay is basically a low-voltage-operated switch [typically 12-14 volts] controlled by the low-voltage room thermostat) that switches a heavier-duty electrical relay to give 120V or 240V electrical power to the compressor/condenser unit.
Most A/C and heat pump contactor relays use an electromagnetic 24-volt two-pole contactor relay that is rated for 30 amps.
The "two poles" simply means that the relay switches two electrical wires simultaneously - which is what you'd expect if your heat pump motor is running on 240 Volts.
Tips for changing out or installing a new magnetic contactor relay on an air conditioner or heat pump
Match the part numbers correctly when installing a new contactor relay in an air conditioner or heat pump. If the coil that activates the relay is not the right one for the compressor motor, you can have either of these problems:
Coil strength is too low: the coil won't reliably energize the start circuit in the motor and the compressor will be hard to get started
Coil strength is too high: the contactor relay coil won't let go of the start circuit: it will keep the start circuit active in the system even after the compressor motor has started - resulting in burning out the starter circuit.
Also locate a magnetic contactor relay switch in the proper physical position (mount it like the original was mounted) don't just hang the relay by its wires (as in our photo above). Some relays may be affected by gravity, either holding points closed too long or not holding the points closed. A current-operated contactor relay (most new units) can be mounted in any position.
Watch out: Some of our readers report successfully replacing minor electrical components such as switches, relays, and contactors. But unless you are qualified to do so we do not recommend trying to do work on electrical systems and components in your home as there are potentially fatal electrical shock hazards. Because air conditioner compressor/condenser units include start/run capacitors (see CAPACITORS for HARD STARTING MOTORS), even when you have turned off power you can get a nasty shock if you're not careful.
Also see SAFETY for ELECTRICAL INSPECTORS and Using DMMs & VOMs Safely. |
Air Conditioner, Heat Pump, Refrigeration System Operating Pressure Control Switches & Electrical Sensor Safety Switches
We distinguish between operating control pressure switches and safety switches that monitor against too-low or too-high refrigerant pressures in a refrigeration system. Both are described in detail at Pressure Controls & Safety Switches. Excerpts are just below.
Operating Pressure Control Switches for Air Conditioners, Heat Pumps, Refrigeration Equipment
Operating pressure control switches set the normal compressor cut-in and cut out pressures in commercial refrigeration systems including air conditioners, coolers, refrigerators freezers.
Commercial refrigeration equipment such as refrigerators (coolers) and freezers use a pressure control switch to set the cut-in and cut out pressures at which the compressor shall operate.
The pressure control switch and the thermostatic expansion valve may both need to be inspected, tested, and set to cooperate with one another, as I describe in an old field service call report described at REFRIGERANT METERING DEVICES TEVs
Shown at left is a Ranco™ single pressure control switch with an operating range of 12-50 psig and a differential range of 5-35 psig. Ranco produces a wide range of switches and controls including air conditioning controllers. This particular Ranco switch shown at left "opens" on low. Available from Grainger and other refrigeration equipment suppliers.
The Ranco Type "O" single function pressure controls are very widely used on refrigeration systems and can operate either as normal operating controls or as protection devices (see Pressure Controls & Safety Switches).
|
Refrigeration System Pressure Safety Switches: protect against over pressure or under pressure in air conditioning or heat pumps
|
 Some HVAC systems (air conditioners, heat pumps, refrigeration equipment) include other sensor switches that may include an electrical pressure or temperature transducer/sensor (photo at left) or an air conditioning or heat pump pressure sensing switch that detects improper (too high) or [in some systems including automotive air conditioning] too-low refrigerant pressures in the system.
Details about these safety switches are at Pressure Controls & Safety Switches. Excerpts are just below.
For safety the air conditioning or heat pump pressure switch can shut off the system. When pressures return to normal the pressure safety switch normally auto-resets and operation can continue.
Watch out: As Ranco and others warn, both under pressure (that can damage the compressor) and overpressure (that can damage or eve blow something up) at an air conditioner or heat pump system - can be dangerous need to be guarded against.
|
List of Inside Air Conditioner or Heat Pump Controls, Switches, Major Parts
Control Circuit Board - Air Conditioner / Heat Pump
|
Control circuits (typically a "control board" shown in our photo at left) along with the contactor relay (discussed above) are used in the compressor/condenser to turn it off and on in response to the indoor thermostat's call for cooling.
While diagnosing a circuit or component problem within an air conditioner or heat pump control board is beyond the skill of most homeowners, a simple visual inspection might show you that the control board has been visibly burned, broken, or damaged. Of course the board may look OK and still be damaged.
See A/C - HEAT PUMP CONTROLS & SWITCHES for details.
|
Air Conditioner or Heat Pump Controls In or On the Air Handler Unit or Blower Compartment & At the Cooling Coil
Air Handler: the air conditioner or heat pump air handler is the "indoor" portion of the cooling (or heating) system whose job is to condition air from the living space by blowing air across a cooling coil (air conditioning) or heating coil (heat pump), sending the conditioned air on through supply ducts into the occupied space. The primary parts of the air handler unit include:
- Return air plenum: return ducts from the occupied space bring building air to this collection point for passage into the air handler
- Air filter: may be located in or near the return air plenum or preferably, at return air registers. Additional air filtration equipment may be installed at the air handler on the return-air side, such as electrostatic air cleaners, UV light sterilizers, HEPA filters, or other air quality improvement devices. See AIR FILTERS for HVAC SYSTEMS for details. Watch out: some HVAC systems may include a clogged or blocked air filter switch that you'll want to check. This may be simply an indicator that pops out to indicate that the filter has become too dirty and is blocking air flow.
|
Thermostatic expansion valves & other refrigerant metering devices:  An air conditioner thermal expansion valve or "TEV" or just "expansion valve" (tan colored device in the photo) is a device located at the cooling coil and connected between the incoming refrigerant line and the refrigerant
inlet to the cooling coil in the air handler.
The thermostatic expansion valve is a refrigerant metering control device, and it is not a control or switch which can be directly operated when using an
air conditioning system, but it is a critical control needed for metering refrigerant into the cooling coil, so we include its description here.
The TEV shown in this photo is used on a heat pump system so it includes extra tubing so that it can permit the refrigerant to reverse its flow
of direction when changing from cooling mode (move indoor heat to outdoors) to heating mode (collect and move outdoor heat to indoors).
There is a variety of refrigerant metering devices and they're not all called "TEVs":
See THERMOSTATIC EXPANSION VALVES for details about the function, inspection, and installation of thermostatic expansion valves, automatic expansion valves, CAPILLARY TUBES, manual and adjustable and non-adjustable expansion valves, high side and low side float valves, all of which are used to control refrigerant flow in refrigeration equipment such as heat pumps, air conditioners, refrigerators, freezers, and dehumidifiers. |
A/C or Heat Pump Air Handler Blower Door Switches
- Blower compartment & blower fan: housing a fan, usually a round squirrel cage fan and electric motor (to operate the fan) which moves air from the return air plenum on towards the cooling or heating coil. An access door to the blower compartment should have a blower door interlock switch, a safety device which will prevent the blower from operating if the door is opened (see below). See FAN AUTO ON Thermostat Switch for details about what turns the blower fan on and off in normal use.
- Blower compartment door switch: an air handler blower compartment access door switch is present on newer units, and can
be seen as a button or switch which is depressed when the blower compartment door or cover is properly in place.
This switch shuts off the blower fan as a safety control if the door is opened. If your air conditioner won't run and someone has been fooling with it, be double sure that the blower compartment door is properly closed and that the interlock switch sensor button or lever is properly depressed to convey that fact to the system.
- Blower motor overload or overheat switch: a built-in overload protector used in some electric motors, especially the electric motor used to power the air handler's blower fan, may be tripped. See Blower Motor Switch for details.
- Cooling coil or heating coil (also called EVAPORATOR COIL or COOLING COIL) through which refrigerant is metered by a thermostatic expansion valve (see below) in order to cool and dehumidify (or in the case of heat pump mode, warm) air from the occupied space as air is blown across this coil.
Backup Heat Controls on Heat Pumps
- Heat Pump Heat & Backup Heat Controls: if your cooling is provided by a heat pump system, during the heating season the same equipment is used to provide heating as was used to provide cooling during hot weather. Heat pumps in climates where temperatures can get lower than the heat pump can handle include a backup heat source and all heat pumps include additional controls: an outdoor thermostat that monitors outside temperature and decides when to switch the backup heating system on; a reversing valve that switches the direction of refrigerant, and an indoor thermostat which can be set to auto, heat, cool, or off modes.
- Supply plenum: a compartment which receives conditioned air from the cooling (or heating) coil and delivers this air to one or more ductwork systems which in turn move air to various areas of the occupied space.
See AIR HANDLER / BLOWER UNITS for details.
Condensate Overflow Pan Safety Switch
 Condensate overflow tray sensor switch: at the air handler, especially in an attic or closet or upper floor air handler, installers may provide an electrical switch (rather than a separate drain pipe) to detect spillage of air conditioner condensate out of its normal air conditioning condensate drain pipe.
When we cool air inside the air handler, that step causes moisture in the air to condense out as a liquid condensate that must be collected and disposed-of.
The condensate overflow switch is a sensor which turns off the air conditioning system as soon as it detects water in the condensate drip tray - thus avoiding a costly leak into building ceilings or floors and perhaps avoiding a mold contamination problem. See DRIP TRAY DEFECTS and Float Switch on Condensate Tray. Thanks to Lester Richter for this tip.
|
Circuit breaker - compressor: in the building main electric panel there will be a switch controlling power to the compressor/condenser unit. Typically this is
a 240V circuit operated by a double pole circuit breaker or a fuse pair.
Circuit breaker - air handler/blower: in the electric panel there will be a circuit breaker or fuse controlling power to the air handler/fan unit which distributes cool air in the building. This will typically be
a separate 120V circuit dedicated to protecting the circuit which supplies electric power to this equipment
Duct System Components, Controls, Switches
Duct System: the air conditioning air ducts (or ductwork) (or heat pump duct work) carry conditioned air from the air handler to various rooms in the occupied spaces of the building.
Return air ducts bring air from the occupied space to the air handler. In some installations only a single return air register and return air duct may be installed, usually in the ceiling over a stairwell in a two-story home; where multiple return ducts are provided you will find two or more return registers in the building; If you observe that most rooms have only a supply register and duct and no individual return air ducts, keeping the room doors open will probably improve air circulation and reduce heating or cooling costs for the building.
Supply air ducts bring air from the air handler (where it has been cooled and dehumidified, or heated if a heat pump is in heating mode) back into the occupied spaces in the building. Where each supply duct enters a room through the room ceiling, wall, or floor, a finned supply register should be installed to permit control of the direction and amount of air that exits the duct at that location.
Zone dampers: HVAC ducts in some installations may include motorized zone dampers controlled by individual room thermostats or switches.
See ZONE DAMPER CONTROLS for details about these controls.
See DUCT SYSTEMS for details about inspecting, diagnosing, and correcting a broad range of HVAC air duct problems.
Duct System Filters on HVAC Systems
|
Filters: air filters provide one or more levels of air filtration should be found installed on any air conditioning or warm air heating system.
Our photo shows an electrostatic air cleaner installed on an air handler. This installation included a disposable air filter installed at a central return air inlet grille (not visible in this photo) so that the air cleaner itself needed cleaning less often.
Air filters may be installed at the return registers, at the air handler, or on occasion at other locations.
See AIR FILTERS for HVAC SYSTEMS.
|
Starter Capacitors and Start/Run Capacitors on HVAC System Motors
A bad starter capacitor or the need for one where none is installed can be the cause of motors that fail to start, motors that chatter or stutter, or electric motors that won't keep running (bad run capacitor). See CAPACITORS for HARD STARTING MOTORS.
Thermostats & Controls on HVAC Systems
|
Thermostats for air conditioning systems or heat pumps:
 |
An air conditioning system thermostat is a switch to turn on or off the A/C equipment as indoor air temperature varies around the thermostat's set point.
The left hand photograph above shows a typical indoor thermostat used to control heating or cooling. Note that in
this photo the thermostat is switched to "heat" mode. The air conditioner will not run with the switch set to "heating".
The right hand photo shows a remote control thermostat used indoors to control the indoor wall-mounted cooling unit of a ductless cooling system.
See THERMOSTATS for details of the operation of air conditioning, heat pump, and heating system thermostats and switches.
More photographs of a ductless air conditioning system are at A/C TYPES, ENERGY SOURCES.
Thermostatic Expansion Valves at A/C or Heat Pump Coils
Another type of thermostat that controls heating and cooling in your HVAC or heat pump system is the TEV or thermostatic expansion valve. This device monitors temperatures at the evaporator coil in the air handler and meters refrigerant into the coil accordingly. TEV devices can fail in several ways, Often involving a clogged sensor tube.
While it's possible to fool around with some TEV's, tap on them, adjust their metering rate, etc. this task should be left to your service technician since without proper training and test equipment you will have little idea where the adjustment has been set (if it can be set).
|
Thermostatic expansion valve:
An air conditioner thermal expansion valve or "TEV" or just "expansion valve" (tan colored device in the photo) is a device located at the cooling coil and connected between the incoming refrigerant line and the refrigerant
inlet to the cooling coil in the air handler.
The thermostatic expansion valve is a refrigerant metering control device, and it is not a control or switch which can be directly operated when using an
air conditioning system, but it is a critical control needed for metering refrigerant into the cooling coil, so we include its description here.
The TEV shown in this photo is used on a heat pump system so it includes extra tubing so that it can permit the refrigerant to reverse its flow
of direction when changing from cooling mode (move indoor heat to outdoors) to heating mode (collect and move outdoor heat to indoors).
See THERMOSTATIC EXPANSION VALVES
for details about the function, inspection, and installation of thermostatic expansion valves. |
Motors in HVAC Systems: Electric Motor Overload or Overheat Reset Switches
There are at least three electric motors in a conventional air conditioning or heat pump system, plus sometimes a fourth:
- An indoor blower fan motor - causing air to move across the evaporator (cooling) coil [or heating coil in heat pump mode], and through the duct work into occupied spaces.
- An outdoor compressor motor - compressing refrigerant gas back into a liquid
- An outdoor compressor unit fan motor - draws air across the condensing coils to condense hot refrigerant gas back to liquid form.
- Condensate pump motor: me systems also use a condensate pump or condensate drain pump to help remove condensate from the air handler to a building drain. A failure here that leads to lost cooling can be subtle: if the condensate removal system fails (bad pump, clogged drain) and if condensate spills into an overflow pan that uses a sensor switch to detect this condition, the failed condensate motor can actually stop an air conditioner from running.
Any of these motors can fail to start or may be "off on reset" due to a motor overload, or motor overheating.
|
Air conditioner fan or blower motor overload reset buttons:
An air conditioner fan or blower motor overload reset button may be present on the blower motor in the air handler/blower compartment.
Look for a red or yellow
button which is normally flat with the motor surface but which will pop up to show that the motor has been shut off by its internal overload protection
circuit.
Some electric motors (such as submersible well pumps and some A/C or heat pump compressors) have an internal thermal reset switch that will reset automatically when the motor cools down. Others such as that shown in our photograph have to be reset manually by pushing the button in when the motor has cooled.
See ELECTRIC MOTOR OVERLOAD RESET SWITCH for details of how to find and how to reset this switch when necessary.
|
Zone Dampers & Zone Controls on Heating and Air Conditioning Systems
Some heating and air conditioning systems use manual or automatic zone dampers to control the flow of conditioned air to different building areas. A manual damper is just a lever somewhere in the duct work that opens or closes a baffle inside the duct to limit air flow through that duct section.
An automatic zone damper may be controlled by an individual thermostat for the area served by that zone. So if the heating or cooling system is not running, or if it is running but not sending air to an area in the building, look for and check out any manual and automatic zone damper controls.
Details about zone dampers used on ductwork: warm air zones and air conditioning zones and zone dampers are at ZONE DAMPER CONTROLS.
If the A/C system will not run check all of these control and safety switches before calling your service technician. If someone has
turned one of these switches off, resetting it may be all that's needed. Not all of these switches will be present on every system; fuses may be used instead of circuit breakers; fuse pullouts
may be used instead of a circuit breaker or fuse at some service switches.
Watch out: Safety warning: do not put your fingers or hands inside of a heating furnace or air conditioner blower or blower compartment without
making certain that all electrical power to the unit has been shut off. If the blower starts turning you can lose a finger, and there are also
electrical shock hazards in these areas.
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.
- 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.
- 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 volume
- LOST COOLING CAPACITY: what to do when not enough cool air comes out of the system
- COMPRESSOR CONDENSER: problems with air conditioner compressor/condenser units
- AIR HANDLER UNIT: problems with the air handler, air filters, and the cooling coil itself
- DUCT SYSTEM DEFECTS: problems with the air duct system, air filters, supply registers, return air registers
- A/C REFRIGERANT LEAK DETECTION: how to use a TIF5000 to detect air conditioning refrigerant gas leak
- A/C DIAGNOSTIC FAQs: air conditioning system diagnostic FAQs: Q&A about air conditioner repair - a detailed air conditioning system diagnostic checklist
Frequently Asked Questions (FAQs)
Click to Show or Hide FAQs
No FAQs have beenn posted for this topic. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Ask a Question or Search InspectApedia
Use the search box below to ask a question or to search the InspectApedia.com website.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Click to Show or Hide Citations & References
- Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- 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
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
- Thanks to Lester Richer, a professional home inspector, for the reminder that a bad air conditioner condensate drip tray switch can shut the whole system down.
- Behr Hella Service A/C pressure switches,
- Grainger, http://www.grainger.com/
- Ranco Corporation, http://www.invensyscontrolseurope.com/ranco/ Tel (Europe)
+44 (0)845 130 5522
- Sensata Technologies, 529 Pleasant Street, B41
Attleboro, MA 02703-2964
Phone: 1-248-692-5600
Fax: 1-248-692-5630
Email: auto-mktg@sensata.com
Web: www.sensata.com, pressure switches for automotive air conditioning systems
- Micro Pneumatic Logic, Inc., Pompano Beach, Florida Tel. (954) 973-6166 - pressure switches
- 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
- Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, 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. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
|
