~IR CONDITIONING FILTERS - Air Conditioning Filter Location, Condition, Problems, Repairs~

First locate and document the placement of the HVAC system air filters - for examination and regular changing during the cooling season.

In our photo at left you can see a blue and white electrostatic air cleaner on the air handler.

But notice at the upper left of the photo just below the brown metal of the air handler body: see that silver sheet metal handle? Removing the two screws on either end of the pull-out will permit you to expose another air filter that is in this location - the handle is a tip-off that the air handler is meant to be opened at this location in order to remove/replace an air filter.

Are these the only two air filters on this system? Nope. Our discussion of cascaded air filters found at OPTIMUM INDOOR AIR FILTERS includes photos of a front-end air filter found at the return air register. In sum, finding a filter on a duct system or air handler is no promise that it's the only air filter installed. Inspect the system thoroughly. If more than one air filter is provided, document the location of all of the filters installed.

Next inspect the air conditioning filter type and condition. What about filters that are missing completely or are very dirty? What problems can a dirty or blocked air conditioner filter cause for the air conditioning system and how do we fix these snafus? That's what we'll cover in this article.

~Air conditioner filter location: filters should be readily accessible~

Filter accessibility: Air filters which are hard to access are rarely changed as often as necessary. I frequently see HVAC systems designed by someone who obviously has never had to service them.

Placement of filters and air handler access doors in very hard-to-access locations such as at the far end of a minuscule attic behind a forest of trusses means that the system is very unlikely to receive the periodic inspection and maintenance it needs.

I prefer to see A/C and heating filters placed at the building side of the air return register or grille, so as to protect the return duct from debris accumulation. The more common filter placement on many systems is right at or in the air handler.

After reading the text just below, if you still cannot find your heating or air conditioning system air filter read our detailed instructions on how to find air filters in our article: Air Filter Location

• At the central air return register, grille located in a wall or ceiling if your system uses centralized air returns instead of individual room-air return ducts. There may be several central return points, depending on the design of your system. If there are more than two, chances are the filter was placed at the air handler instead of at these grilles. Unfortunately that means that the return ducts themselves become more soiled with dust and debris from the building.
  
  
• At an attic air handler look for a slot which has a removable cover. The slot may be just an inch or so wide if 1" thick filters are used, or it could be several inches wide if a wide high-capacity pleated or similar filter was used. The return air plenum on an attic or basement air conditioner blower unit will usually be a large metal enclosure about the same dimensions in width and height as the air conditioner blower unit itself. Look for a filter slot right where the return plenum contacts the blower fan assembly.
  
  
• At a basement air handler we also look for a filter at the return air plenum which is often next to the bottom of the air handler if the system is an "up-flow" unit (or vice versa for the less common case of return air entering at the top of the air handler and exiting at its bottom).
  
  
• Next to an electrostatic air cleaner: if your air conditioning air handler has an electrostatic air cleaner installed, look for the filter, if there is one, next to the electrostatic air cleaner. In addition, the electrostatic air cleaner, which is a type of particle incinerating filter itself, needs to be removed and cleaned periodically. (Check with your unit's manufacturer for cleaning interval and procedures. Often the electrostatic unit can be cleaned inside a dishwasher). Often there is also a thin metal washable air filter installed along with the electrostatic air cleaner.

Change your air filters every month when the air conditioning system is in operation. Make sure you find all of the filters as some systems have multiple filters and even multiple types of filters installed, such as a fiberglass or pleated paper filter, a washable filter, and an electrostatic air cleaner. These last two are cleaned, not replaced, when they're dirty.

~Dirty Air Conditioner Filters Cause Multiple Problems for an Air Conditioning System~

Dirty Air Filters: are a source of increased operating costs and poor cooling system operation. Dirty air filters can: reduce air flow in the building cause dirt to accumulate on the fan blades, wasting your energy dollars cause excessive dirt build-up inside the duct system, leading to mold or allergen problems in a building and to the need for more costly duct cleaning or replacement block the cooling coil itself with dirt, reducing system effectiveness and possibly leading to costly repairs lead to frost build-up on the cooling coil and reduced or totally blocked air flow in the system eventually permit dirt to bypass the filter where it soils and blocks the blower fan itself, leading to more costly repairs. The filters on an air conditioning or hot air heating system should be changed monthly when the system is in use. Discuss with your heating/cooling service professional the possible need to clean the blower fan and duct work.

~Improperly-Fit or Wrong Sized Air Filters Cause Bypass Leakage~

Bending over the end of an air conditioner or heating air handler filter such as shown in the photo at left above is a bad idea. If the filter does not fit there will be bypass leakage past the filter, soiling the blower fan, slowing air flow, and leading to more costly cleaning and service later.

Furthermore when you bend the filter as this owner did, you interrupt the structural integrity of the filter's frame, risking filter collapse. A collapsed air filter can be drawn right into the blower fan, causing damage to the fan motor or even leading to a fire!

The photo at right shows how a college HVAC maintenance crew kept the A/C system running when the school did not have the proper filter size in stock. This filter installation also will have severe bypass leakage around the filter where the pleated section contacts the edges of the filter slot.

Installing a filter that is the wrong size for the heating or air conditioning air handler defeats the purpose of air filters because of leakage and it may be unsafe. Install a properly-sized filter in locations like this as soon as possible and watch out for unsafe filter collapsing.

~How to Construct or Obtain Large or Special-dimension HVAC System Air Filters~

The same college HVAC maintenance staff who was struggling with improperly-fit air filters we discussed earlier was also faced with the task of coming up with a much larger air filter for the air conditioner air handler over their computer center. The neatly-taped "built-up" air filter shown in this photo was nicely constructed but we don't recommend this practice: The filter may come apart and send fragments into the blower assembly, damaging the blower or leading to overheating and a fire. The filter is not delivering the total cross-section of filtering area that was anticipated by the HVAC design engineer who specified the dimensions of the return air plenum at which this filter was installed - we're seeing less total CFM of airflow.

Air filter suppliers and manufacturers have no trouble providing air filters of special dimensions. Furthermore if the filter is built by a manufacturer it's more likely that they'll understand the structural and strength requirements of the filter as well as the required airflow characteristics and filtering ability. We list some suppliers of air filters at SOURCES FOR AIR FILTERS

Incidentally, except unusual cases with special requirements, wouldn't it have made sense for the HVAC or duct system designer to have specified a filter that is one of the many standard sizes?

~Missing Air Conditioner Filters~

Look closely at this photograph. On the right we can see a tan "Air Filter Cover" plate which marks the intended location of the HVAC air filter. But there is an open slot to the left of the air filter cover, possibly where another filter was previously being installed. When the new air filter slot was constructed and nicely covered (so as not to leak) the old slot was simply left open. You can see my piece of adhesive tape bending into the opening, demonstrating (not too scientifically) that there was airflow into the unit from this location. This is a great way to draw attic insulation fiberglass into the air handler and to blow it into the living area. And of course any other unwanted attic dust and debris is also being invited into the air handling system and blown into the occupied space. Failure to properly filter dust from the return air supply will load the fan and cooling coil, dirty the duct system, and lead to the problems listed above. As the ductwork debris level increases you increase the risk of forming an allergen or mold reservoir, especially if there are water or condensate leaks into the duct system interior. If a filter is not present, have one installed. Installing a filter is normally a minor expense. Duct cleaning or duct replacement can be a significant expense. Cleaning up a moldy HVAC system, where mold may have been caused by coil icing which was caused by a dirty coil or filter is still more costly. What are the Components of the Outdoor Portion of a Central Air Conditioning System - the Air Conditioning Compressor Unit? The (usually) outdoor half of a typical air conditioning system is a unit containing the refrigerant compressor and condensing coil. The compressor draws refrigerant gas from the building's inside components, and compresses the gas to high pressure. The condenser coil then cools the high pressure high temperature gas to a liquid state. The heat produced in these steps is transferred to the outside by a fan which blows outside air across the condensing coil. The liquid refrigerant is then able to return to the indoor components for cooling and dehumidifying the building interior. The diagnosis and repair of various defects in the air conditioning compressor/condenser unit are discussed in detail using the links provided at the left of this page. Here is a little more detail about the components of the compressor/condenser unit: The Air Conditioning Compressor Itself - on residential units the A/C compressor motor is most often a hermetic motor-compressor combined in a single sealed unit like the Carrier(TM) unit shown at above left. If a ductless split-system is installed an outside compressor unit is still required, typically looking like the Sanyo(TM) unit shown at the top of this page. The compressor is a basically a pump which moves refrigerant gas to the compressor via the larger refrigerant "suction line" returning it from the in-building air handler and evaporator coil. The compressor compresses the refrigerant to a high pressure gas and moves that gas into the condensing coil described just below. The refrigerant gas leaves the compressor at high pressure and at high temperature (since compressing a gas will raise its temperature.) Refrigerant lines: the larger diameter refrigerant suction line connects the indoor evaporator coil outlet to the compressor inlet. The smaller-diameter high pressure refrigerant lines connect the compressor outlet and the condensing coil inlet and also move refrigerant liquid in it's cooled, condensed and now liquid state from the outlet of the condensing coil to the thermal expansion valve (basically a refrigerant metering device) and the evaporator coil inlet in the air handler unit in the building. Service valves or ports are usually present on the refrigeration lines near the compressor. to permit testing the condition of the air conditioning system and permit removal, replacement, or additions to the refrigerant in the system. Condensing coil receives high pressure refrigerant gas from the compressor and cools this refrigerant gas back to a liquid state. Outdoor cooling fan moves outdoor air across the condensing coil to cool it and assist in condensing the high pressure, high temperature refrigerant gas back into a liquid. It is this process which completes the transfer of heat through the refrigerant from indoor air to outdoor air as the compressor/condener unit compresses and then cools the refrigerant back to a liquid. Electrical shut-off switch(es) for service at the unit are provided to permit maintenance and repair of the equipment. Circuit breaker(s) at the electrical panel protect the circuit supplying power to the air conditioning system. These components are discussed in detail throughout this website using the links at the left of these pages. ~Minimum Air Conditioner Compressor Unit Observations for an Air Conditioner Report~ The compressor and fan operated normally. The rated cooling capacity, estimated age and general condition of the unit are reported below. OR ... We did not operate this equipment because ... so you should ... .

Critical Defects in Air Conditioning Equipment Inspections

Critical defects which an inspector should not fail to detect when examining any building component or system are defects which form an immediate, significant safety hazard or defects which are quite likely to involve significant repair or replacement cost, and which involve components or systems which are necessary to occupy and use the building. Methods for detection and diagnosis of these defects are discussed in this document and in its references. Suggestions for inclusion or exclusion of items in this list are invited - see the link "Contact Us".

• Function: Air conditioning compressor needs replacement
• Function: Cooling is delivered to only part of the building, e.g. only to one floor.
• Safety: Unsafe return air intake which may draw in carbon monoxide at heating equipment
• Uneven air supply resulting in uneven temperatures especially on the first floor of a two story house with ductwork between the first and second floor.
• Inadequate cooling capacity for building.
• Low temperature split (indicating inadequate cooling due to refrigerant leak)
• Refrigerant leaks at condenser or evaporator coils (usually requires replacement of coil.)
• Dirty air handler. (Major expense to clean properly.)
• Leaking return ducts in crawl space
• Safety: Unsafe electrical wiring: aluminum branch circuits and FPE Stab-Lok or Zinsco circuit breakers may have been used to power the compressor. Look for evidence of overheating or over fusing at the service cutoff and in the electrical panel and at the service cutoff by the compressor/condenser [This item is not agreed-on as a critical defect by all reviewers]

  CONDENSATE TRAY CLEANING - Cleaning suggestions for A/C System Condensate Systems

  Should we disinfect cooling system equipment or condensate trays?

  Should we be putting bromide or chlorine tablets in our condensate trays to keep bacteria from growing?

  If we should be, then do we need to alternate bromide with chlorine on some type of frequency to prevent development of resistant bacteria?

  We're discussing condensate trays from mechanical equipment like heat pumps, fan coil units and air handlers with AC coils.

  These pieces of equipment have condensate trays which are then drained through a small pipe, usually clear, but not always, with a trap in it, to a drain.

  These condensate trays have some standing water in them when the AC is functioning. Should these condensate trays be treated with an algaecide of some sort?

  There are risks beyond mold and algae, in particular Legionella bacteria (legionnaire's disease) which can have an alarmingly high mortality rate, and also potential hazard sources such as biofilms that can include other bacterial and maybe other pathogens. However the risk of formation of problem levels of mold, bacteria, or other pathogen is probably not the same across all buildings nor types of equipment, and much of the risk may depend on installation and maintenance details at individual installations.

  Particularly in climates with a high humidity and a heavy cooling load, and depending on details of the design and installation of the air handler unit and duct work, there is risk of blowing pathogen-contaminated water droplets downstream inside the air conditioning duct work and thus exposing building occupants. With rooftop-mounted cooling units such as cooling towers using water, conditions may be still more attractive for growth of pathogens and there is some risk of movement of pathogens out of the cooling equipment to people located nearby and downwind from the equipment, even if they are outside the building which the equipment actually serves.

  While I am not expert on this topic I have collected and provide here some key information and opinions to help sort out these questions. Use the links at page left to read additional details on this topic including recommended cleaning procedures and details of the Leginella hazard in air conditioning systems, humidifiers, etc.

  1. A/C COMPONENT LIST - Basic Air Conditioning Components Inspection List

  Conventional cooling systems include the following components:

  The air conditioning system (and heat pump) components introduced here are discussed in detail and are illustrated by photographs and drawings throughout this website using the links at the left of these pages. We explain how to inspect, diagnose, repair, or select, purchase, and install air conditioning systems or their individual parts and components.

  List of Indoor Components of an Air Conditioning System

• Air Handler Unit (AHU) (shown at left above) which typically includes the following
• Condensate system: water, or condensate is produced when we cool warm moist air by blowing it over the evaporator coil. The condensate runs down the coil to a collecting pan which drains to piping used to route condensate to an approved drain for disposal
• Condensate pump on some air conditioning systems a small pump is used to collect and then pump condensate up to a building drain or other location for disposal. Condensate pumps are needed for systems which cannot dispose of the condensate by simple gravity flow down a drain line.
• Condensate overflow pan or tray is a container placed below the air handler when that unit is located in an attic or in other building locations where condensate leakage or overflow would otherwise spill onto building floors or into a building ceiling. The condensate overflow pan is a safety device intended to prevent unwanted spillage; normally it does not contain condensate. The condensate overflow pan should have either an independent drain to an approved location or a float switch to shut down the air conditioner should the pan become full.
• Blower fan in a blower compartment circulates building air into itself from the return ducts and return plenum, and moves that air across the evaporator coil and onwards to the supply plenum and supply ducts in the building. Blowers may be single speed, multiple speed, or variable speed, and may need to move air at different rates if the blower is used for both heating and cooling in the same duct system. Some air blowers are also rated for continuous operation.
• Electrical controls for an air conditioning system include shut-off switch(es) for service at the unit and fuses or circuit breaker(s) at the electrical panel. The fuse or circuit breaker protects the air conditioner circuit from overheating due to an overcurrent or other electrical failure.
• Evaporator Coil (also called the "cooling coil" is connected to high pressure and low pressure (suction) refrigerant lines. High pressure refrigerant liquid, released into the cooling coil by the thermal expansion valve changes state from a liquid to a gas, causing a drop in temperature of the refrigerant and thus cooling the evaporator coil so that when we move air across the coil the air will, in turn, be cooled.
• Return Plenum, connected to return duct system, is the air receiving compartment which provides air to the blower fan.
• Supply plenum connected to supply duct system, is the air collecting compartment to which building supply ducts are connected. Think of the return plenum and supply plenum as junction boxes to which return ducts or supply ducts respectively can be connected.
• Support system is the means by which an attic-mounted air handler is supported or held in place, for example by being suspended from the roof rafters (a quiet installation) or perhaps by being placed on supporting wood beams laid across ceiling joists.
• Thermal expansion valve: an air conditioner thermal expansion valve 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 air conditioning system thermal expansion valve or "TEV" is a metering device which regulates the flow of refrigerant from the incoming high pressure side (from the compressor/condenser) into the low pressure side (in the cooling coil). This valve maintains the pressure difference (high and low) at the entry point to the cooling coil, thus assuring that as the high-pressure refrigerant enters the low pressure space of the cooling coil, it can "evaporate" from a refrigerant liquid to a gaseous form, thus producing the temperature drop that cools the cooling coil itself. (All cooling systems using refrigerants use some type of expansion valve, of varying complexity. Even a simple window air conditioner or a refrigerator make use of an expansion valve, in the form of a small-diameter capillary tube or "cap tube" which meters refrigerant into the cooling coil.)
• Air Filters located at the return duct air inlets, at one or more central return air inlets, or at the air handler unit itself are used to remove dust and debris from building air.
• Access ports to duct interior Commercial ducts and some residential duct systems may have inspection/cleaning access ports; residential HVAC ducts may have plugs indicating that the ducts have been cleaned in the past.
• Ductless air conditioning systems, which may also be called "split A/C systems" may employ one or more wall mounted cooling units such as shown at right above
• Return air ducts and registers collect warm moist air from the occupied space and return it to the air handler unit. Some air conditioning installations do not provide return air registers and ducts in every room and use one or more "central air return inlets" instead. Central air returns are most common on air conditioning retrofit installations (adding A/C to an existing building).
• Supply air ducts and supply air registers deliver cooled air to the occupied space. Supply registers have the dual function of spreading out and directing the air flow into a location and permitting the regulation of air flow by opening or closing the register. Some air conditioning duct systems use small-diameter, "high velocity" ducts to deliver conditioned air to the living space.
• Supply air balancing dampers, manual and motorized zone dampers may be installed inside the supply ducts at varying locations in to permit balancing the air flow among different duct sections and thus among different building areas.
• Thermostat(s) are used to turn the air conditioning on and off and to set the desired indoor temperature. One thermostat will be located in each different air conditioning zone and will control an individual air handler unit's operation.

These components are discussed in detail and are illustrated by photographs and drawings throughout this website using the links at the left of these pages.

CONDENSATE HANDLING - Air Conditioning Condensate Handling Defects

Improper handling of air conditioning system condensate is one of the most commonly reported set of A/C system defects, perhaps in part because these defects are easily observed visually, and perhaps also because some A/C installers do not follow basic plumbing and building code requirements for handling the discharge of the condensate produced when an air conditioning system is operating. Condensate leaks or discharge errors (such as the drips into the dog bowl and cooking pot in this attic) present several risks of ugly surprises in buildings including:

First locate and document where condensate discharge is carried

• a plastic line draining outside.
• a floor drain
• a sump pit
• a hole in the floor
• a reservoir lift pump which pipes condensate to: (a properly connected building drain; something else)
• the pump exit line is taken to the house main waste line
a dirt floor or crawl space

Look for corrosion or water stains on floor surfaces around the equipment, at the condensate drip pan and at bottom of the "A frame" cooling coil, indicating that the drain may need cleaning and more important, indicating that the condensate is leaking out of the equipment or drains and not being carried to an acceptable disposal point.

List of Outdoor Air Conditioning System Components

1. Compressor motor - on residential units this is normally a hermetically-sealed motor-compressor combined in a single unit like the Carrier(TM) unit shown at above left. If a ductless split-system is installed an outside compressor/condenser unit is still required, typically containing the very same functions but perhaps more compact, looking like the Sanyo(TM) unit shown at above right. An air conditioning compressor is a specialized pump which draws refrigerant gas back to the compressor/condenser unit from the in-building air handler and evaporator coil. The compressor compresses the returning low-pressure refrigerant gas to a high pressure (and high temperature) form. In a "split" air conditioning system, multiple indoor evaporator coils and blower units may be served by a single outdoor compressor unit such as the Sanyo unit shown at the top of this page. That unit was handling the compressor/condenser function for two wall-mounted, ductless indoor cooling units, one of which is shown in the right hand photo at "List of Indoor Components" above. Split systems like this do not make use of ductwork.
2. Condensing coil receives high pressure refrigerant gas from the compressor and cools this refrigerant gas back to a liquid state.
3. Electrical controls: shut-off switch(es) for service at the unit are provided to permit maintenance and repair of the equipment. Circuit breaker(s) at the electrical panel protect the circuit supplying power to the air conditioning system.
4. Fan an outdoor cooling fan in the compressor/condenser unit moves outdoor air across the condensing coil to cool it and assist in condensing the high pressure, high temperature refrigerant gas back into a liquid. It is this process which completes the transfer of heat through the refrigerant from indoor air to outdoor air as the compressor/condenser unit compresses and then cools the refrigerant back to a liquid.
5. .

   Refrigerant lines: these pipes, typically made of copper, include a low-pressure "suction line" which returns low pressure refrigerant gas from the indoor evaporator coil (cooling coil) outlet to the outdoor compressor motor inlet. The high pressure refrigerant line connects the compressor outlet to the outdoor condensing coil inlet (gas) and further connects the condensing coil outlet to the indoor thermal expansion valve which meters high pressure refrigerant into the "low-side" evaporator coil (cooling coil) in the air handler unit in the building.



Service valves or ports are usually present on the refrigeration lines near the compressor. These valves permit testing the condition of the air conditioning system and permit removal, replacement, or additions to the refrigerant in the system. This photograph of a split system compressor/condenser outdoor unit shows four refrigerant lines and their sets of service ports. The larger diameter copper pipes are the low pressure or suction lines and the smaller diameter pipes are the high pressure lines returning refrigerant to the indoor cooling units. The screw caps visible at the piping connectors where they enter the unit can be removed to provide access to special connecting valves to which the service technician can connect her set of gauges to measure system operating pressures on these lines.

Do not mess with these refrigerant service ports unless you're a trained A/C service technician. You may lose refrigerant or contaminate the system, leading to improper system operation or a costly service call.

~OPERATING CONTROLS - Air Conditioning System Operating Controls~

Basic air conditioning inspection and inspection report information for A/C controls:

1. Thermostats: The air conditioning system is operated by thermostat in the living area. If multiple air handling units and compressors are installed you should find a thermostat for each area served by that equipment.
2. Air conditioning system zone dampers: Some air conditioning system designs may use a single air handler and compressor, but may add zone dampers in the duct work to provide individual "zoning" of cool air distribution. In this case each zone thermostat both calls for the system blower/compressor to operate and also causes a motorized zone damper to open to direct cool air to a particular portion of the building. An ordinary home inspection is unlikely to address proper operation of motorized zone dampers.
3. Manual duct dampers may also be present in duct work to manually balance air distribution among building areas. Be sure to look for these when diagnosing poor cool air delivery to an area.) Also see our note below about the presence of multiple switches and controls.
4. Electrical switches for air conditioning systems will often be found as follows: (some of these may be absent on some systems)
• 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

  ~SAFETY CONTROLS - Air Conditioning Automatic Safety Controls - Cooling System Fuse or Circuit Breaker Size Requirements~

  ~Electric Power Controls - Safety Disconnects for Air Conditioners~

  Safety disconnects should installed outside next to the compressor/condenser unit and are often also installed next to or mounted on the air handler/blower unit.

  If you cannot find an outside electrical disconnect one should be installed. These controls are recommended for safety to reduce the temptation to open the cabinet and work on the equipment with power on. Working on electrically "live" cooling equipment risks both shock and mechanical injury such as being cut by the fan if the motor starts unexpectedly. Safety shutoffs are required for new equipment.

  ~How to Specify the Breaker or Fuse Size for Air Conditioning Circuits~

  Amperage rating of safety disconnects and A/C circuit breakers: the safety switch on newer equipment may be a simple pull-out fuse-block type power disconnect, leaving circuit protection to be provided only at the circuit breaker or fuse for the A/C circuit where it originates in the electrical panel. Where the actual overcurrent protection is provided (at older circuit breakers used as auxiliary safety disconnects at the equipment, and at the main panel at the origin of the cooling circuit for the compressor/condenser unit) electrical overload protection size (circuit breaker or fuse amperage rating) for modern A/C equipment is specified by the manufacturer.

  The Maximum Fuse or HACR type Breaker: specifies the maximum overcurrent protection or MOP to be used to protect the equipment. The permitted ampacity of the equipment electrical circuit protection (fuse or circuit breaker amps) expressed as MOP or Maximum Overcurrent Protection. If MOP is specified, the breaker or fuse protecting the equipment should match this number.

  As we explained at the beginning of this document, a hermetic compressor draws varying amounts of current (measured in amps) as its internal pressure changes during operation. We said that current draw is higher when starting the motor than when the system is in steady state operation. Current draw is highest if the motor is starting against its highest back pressure such as if the air conditioning system has been turned off and then back on in the middle of operation. Because fusing an air conditioning compressor at the minimum level can result in blown fuses or tripped breakers during these intervals of heavy current draw during compressor startup, compressors are either protected by a slow-blow fuse or a somewhat larger than minimum circuit breaker.]

  Rules of thumb for over sizing air conditioning system breakers or fuses: On some older equipment MOP is not specified. Only when MOP has not been specified can the overcurrent protection required be determined by alternative means such as [RLA OR BCSC whichever is greater x 175%], or if the compressor keeps tripping that device or blowing that fuse, RLA x 225% might be used. The National Electrical Code (NEC) specifies the degree to which a breaker or fuse may exceed the RLA. [For example, if the MOP or fuse size is specified by the manufacturer to be 40 amps, then a 40 amp breaker must be installed with no increase or change in that rating.]

  Multiple switches are often present on cooling systems. As we reminded in the previous chapter, if the air conditioning system won't run, before requesting a service call check all of the switches as well as the thermostat for proper settings.

  ~Air Conditioner Fuse or Circuit Breaker Size Details~

  Generally, what is the ampacity we see in the field when inspecting an air conditioning compressor circuit?

  When the air conditioning system is running, if you measured the amperage, it would be roughly 80% of the RLA. The breaker size is typically about 125% of the total of the compressor RLA and the condenser fan FLA (full load amperage).

  The rationale is that the circuit breaker protecting the air conditioner compressor unit should trip in the event of a locked rotor [the revolving axle of a compressor motor, for example] or some significant electrical event, but should not trip during start up loads which, as we know can be significantly higher than the RLA momentarily [as the compressor motor draws higher amperage to get itself started].

  Why can we put an "oversized" fuse or circuit breaker on an air condtioning compressor circuit?

  An air conditioning electrical circuit is different than a general household circuit in that we have a known current load. [There is only one device connected to the air conditioning electrical circuit, and we can read its operating characteristics.] We are not worried about an overload situation where people plug several appliances into receptacles on a single circuit. Generally speaking, the amperage draw is fine or is way too big.

  Section E3602.10 of the IRC says, "Branch circuits for air conditioning and heat pump equipment. The ampacity of the conductors supplying a multimotor and combination load equipment shall not be less than the minimum circuit and capacity marked on the equipment. The branch-circuit overcurrent device rating shall be the size and type marked on the appliance and shall be listed for the specific purpose." In short, do what it says on the dataplate.

  ~How to Diagnose & Repair an Air Conditioner Compressor Which has Lost Cooling Capacity~

  A compressor which appears to have lost cooling capacity can be diagnosed by a service technician who can connect the appropriate test gauges to the system. Lower than normal discharge pressure and higher than normal suction vacuum will indicate this problem. But before assuming that something is wrong with the air conditioning compressor, some basic investigation is in order. Unless there is an obvious indication of a compressor problem (noise, hard starting, compressor won't start), the service technician, to be thorough and economical, will inspect the system in an order, checking the easy and least-costly problems first, such as presence of electrical power, proper setting and operation of system controls, condition of filters, condition of duct work, operation of blower fans, before moving on to check the compressor itself by looking at the air conditioner operating temperatures, pressures, and current draw in Amps.

  ~Cooling Capacity of the Air Conditioning Equipment~

  The cooling capacity of an air conditioning equipment refers to the ability of the compressor/condenser (usually outside) and the air handler/evaporator (usually inside) to deliver cool air to the occupied space. Briefly, the compressor/condenser draws refrigerant gas from the building air handler, compresses it and cools it back to a liquid refrigerant, and the air handler/evaporator coil permits liquid refrigerant to evaporate inside a cooling coil, across which the fan blows building air to cool and dehumidify it. The particular combination of this equipment has a cooling capacity, usually rated in BTUh or thousands of BTU's of cooling capacity per hour, documented on equipment data tags discussed above at "RATED COOLING CAPACITY" - see links at left.

  ~Air Conditioner Long "on" cycle and Insufficient Cooling - Loose or Worn Compressors~

  A longer than normal "on" cycle combined with little or no cool air conditioner output could be due to an inefficient air conditioning compressor or one which has lost its ability to "compress" the refrigerant due to internal wear. This condition can be diagnosed by an air conditioning service technician who will install air conditioning manifold gauges onto the system to check the compressor suction vacuum and discharge or "high side" output pressure. If gauge ports are not installed on the air conditioner compressor unit the technician cannot make this test without cutting the refrigerant lines to install gauge ports (adding to the cost of this diagnosis).

  ~Low air conditioner motor amperage draw~

  Low amperage draw: unlike a high-amp current draw which indicates that the compressor is danged internally in a way that its piston(s) is(are) tight in the cylinder, a low-amp current draw, if below normal, may confirm internal wear on the compressor parts, and would support the diagnosis that the compressor is worn and inefficient. Where there are no gauge ports to actually measure compressor low side and high side vacuum and pressure, this simple electrical test is a useful first step.

  ~Abnormal air conditioner compressor pressure readings~

  Refrigerant line pressure readings which are abnormal (probably too low) on the high pressure side (compressor output) or on the low pressure side (compressor input or suction line) can indicate a problem with the compressor's ability to develop normal operating pressure ranges and thus will affect the cooling capacity of the air conditioning system. For more details on air conditioner refrigerant line pressures and how they are examined see COMPRESSOR PRESSURE READINGS

  ~Cooling Capacity of the Air Conditioning Duct System~

  Even if a very high BTUH capacity cooling system is installed, if the duct system is defective the ability of the system to deliver cool air to the occupied space can be severely or even totally lost. Duct System Efficiency (in percent) describes the percent of cooled air produced by the A/C equipment which is actually delivered to the occupied space. This number is less than 100% because of air flow restrictions and losses in the duct work. Duct Delivery Effectiveness is the percent of cooling capacity which is delivered through the registers into the occupied space. Registers themselves restrict air flow. See "DUCT SYSTEM DEFECTS" - see links at left.

  Cooling Capacity of the Whole Air Conditioning System

  So the ability of the entire A/C system to cool a building or rooms in it requires that both the cooling equipment and the duct system be in proper working order.

  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.

• Clogged 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.
• 
  
• Damaged cooling 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.
• Cooling Coil Ice-Up 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
• Improper refrigerant charge - too little: an air conditioner system which has lost some (but not most) of its refrigerant will sometimes run too cold at the evaporator coil, leading to coil icing and loss of cool air delivery in the home. If the filters are clean and the coil ices-up this condition may be present. A service technician will need to evaluate and test the system and if needed, adjust the refrigerant charge.
  Watch out for refrigerant leaks that lead to a repeat of this problem. If the system is low on refrigerant because it has a leak, it is much smarter to find and fix the leak than to simply keep adding refrigerant. If you keep adding refrigerant to a cooling system you're leaking possible contaminants into the environment as well as wasting money.
• Improper refrigerant charge - too much can also lead to improper air conditioning system operation and in some cases can damage the compressor. A service technician will need to evaluate and test the system and if needed, adjust the refrigerant charge. In this case the cooling coil is probably not going to ice-over, it just won't get cool.
• Loss of most refrigerant from an air conditioning system means that the cooling coil will not get cool at all. A service technician will need to evaluate and test the system and if needed, find and fix the refrigerant leak, evacuate the system, and install the proper refrigerant charge.
• Compressor problems such as an aging cooling compressor 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.

~PENEMUAN AWAL PENYEJUKAN~

Penyejukan iaitu Perindustrian menyimpan makanan mula menjadi kepentingan perdagangan pada kurun ke 18. Penemuan awal Penyejukan di mana ais yang didapati di kolam atau tasik pada musim sejuk di potong dan disimpan di bilik yang berpenebat kemudian di gunakan pada musim panas. Pada tahun 1834 seorang jurutera Amerika iaitu Jacub Perkins telah mencipta sejenis alat pembuatan ais yang kemudiannya tercipta sistem pemampatan. Pada tahun 1855 seorang jurutera German memperkenalkan alat Penyejukan Penyerapan ( absorbtion system ) berdasarkan oleh Micheal Faraday pada tahun 1824 ( sistem Pengewapan ). Pengeluaran ais buatan menjadi penting pada tahun 1890 apabila ais asli mula berkurangan, sejak itu pertumbuhan industri Penyejukan Mekanikal bertambah. Pada tahun 1913 J.M Larsen mengeluarkan sistem Penyejukan Mekanikal dengan kawalan manusia. Kemudian pada tahun 1918 Kelvinator mengeluarkan Peti Sejuk automatik untuk pasaran Amerika sahaja. Pada tahun tersebut juga 67 unit telah di jual dan antara tahun 1918 dan 1920 sebanyak 200 unit juga telah terjual. Unit Penyejukan jenis Hermatik atau seal yang pertama di perkenalkan oleh General Electric pada tahun 1928. Alat tersebut dinamakan Monitor Top. Pada tahun 1927 Electrolux mengeluarkan sistem Penyerapan automatic. Penyejukan automatik iaitu Penyamanan udara untuk keselesaan manusia atau haiwan di dapati pada tahun 1927. Pada awal 1930 Penyamanan udara Automobil meluas digunakan. Selepas 1940 semua unit Penyejukan yang dikeluarkan adalah jenis tertutup dan sistem berkeupayaan besar juga mula di buat dan digunakan. Pada masa sekarang penemuan-penemuan industri Penyejukan dan Penyamanan udara yang menabjubkan telah meluas di keluarkan dan di gunakan. Hampir semua syarikat yang terlibat pada masa kini memikirkan bagaimana untuk mengurangkan penggunaan arus elektrik dan memberi keupayaan yang lebih kepada pengguna.

PENEMUAN AWAL PENYEJUKAN

Penyejukan iaitu Perindustrian menyimpan makanan mula menjadi
kepentingan perdagangan pada kurun ke 18. Penemuan awal Penyejukan di mana
ais yang didapati di kolam atau tasik pada musim sejuk di potong dan disimpan di
bilik yang berpenebat kemudian di gunakan pada musim panas.
Pada tahun 1834 seorang jurutera Amerika iaitu Jacub Perkins telah
mencipta sejenis alat pembuatan ais yang kemudiannya tercipta sistem
pemampatan.
Pada tahun 1855 seorang jurutera German memperkenalkan alat Penyejukan
Penyerapan ( absorbtion system ) berdasarkan oleh Micheal Faraday pada tahun
1824 ( sistem Pengewapan ).
Pengeluaran ais buatan menjadi penting pada tahun 1890 apabila ais asli
mula berkurangan, sejak itu pertumbuhan industri Penyejukan Mekanikal bertambah.
Pada tahun 1913 J.M Larsen mengeluarkan sistem Penyejukan Mekanikal dengan
kawalan manusia. Kemudian pada tahun 1918 Kelvinator mengeluarkan Peti Sejuk
automatik untuk pasaran Amerika sahaja. Pada tahun tersebut juga 67 unit telah di
jual dan antara tahun 1918 dan 1920 sebanyak 200 unit juga telah terjual.
Unit Penyejukan jenis Hermatik atau seal yang pertama di perkenalkan oleh
General Electric pada tahun 1928. Alat tersebut dinamakan Monitor Top. Pada tahun
1927 Electrolux mengeluarkan sistem Penyerapan automatic. Penyejukan automatik
iaitu Penyamanan udara untuk keselesaan manusia atau haiwan di dapati pada
tahun 1927. Pada awal 1930 Penyamanan udara Automobil meluas digunakan.
Selepas 1940 semua unit Penyejukan yang dikeluarkan adalah jenis tertutup dan
sistem berkeupayaan besar juga mula di buat dan digunakan. Pada masa sekarang
penemuan-penemuan industri Penyejukan dan Penyamanan udara yang
menabjubkan telah meluas di keluarkan dan di gunakan. Hampir semua syarikat
yang terlibat pada masa kini memikirkan bagaimana untuk mengurangkan
penggunaan arus elektrik dan memberi keupayaan yang lebih kepada pengguna.

PENEMUAN AWAL PENYEJUKAN

Penyejukan iaitu Perindustrian menyimpan makanan mula menjadi
kepentingan perdagangan pada kurun ke 18. Penemuan awal Penyejukan di mana
ais yang didapati di kolam atau tasik pada musim sejuk di potong dan disimpan di
bilik yang berpenebat kemudian di gunakan pada musim panas.
Pada tahun 1834 seorang jurutera Amerika iaitu Jacub Perkins telah
mencipta sejenis alat pembuatan ais yang kemudiannya tercipta sistem
pemampatan.
Pada tahun 1855 seorang jurutera German memperkenalkan alat Penyejukan
Penyerapan ( absorbtion system ) berdasarkan oleh Micheal Faraday pada tahun
1824 ( sistem Pengewapan ).
Pengeluaran ais buatan menjadi penting pada tahun 1890 apabila ais asli
mula berkurangan, sejak itu pertumbuhan industri Penyejukan Mekanikal bertambah.
Pada tahun 1913 J.M Larsen mengeluarkan sistem Penyejukan Mekanikal dengan
kawalan manusia. Kemudian pada tahun 1918 Kelvinator mengeluarkan Peti Sejuk
automatik untuk pasaran Amerika sahaja. Pada tahun tersebut juga 67 unit telah di
jual dan antara tahun 1918 dan 1920 sebanyak 200 unit juga telah terjual.
Unit Penyejukan jenis Hermatik atau seal yang pertama di perkenalkan oleh
General Electric pada tahun 1928. Alat tersebut dinamakan Monitor Top. Pada tahun
1927 Electrolux mengeluarkan sistem Penyerapan automatic. Penyejukan automatik
iaitu Penyamanan udara untuk keselesaan manusia atau haiwan di dapati pada
tahun 1927. Pada awal 1930 Penyamanan udara Automobil meluas digunakan.
Selepas 1940 semua unit Penyejukan yang dikeluarkan adalah jenis tertutup dan
sistem berkeupayaan besar juga mula di buat dan digunakan. Pada masa sekarang
penemuan-penemuan industri Penyejukan dan Penyamanan udara yang
menabjubkan telah meluas di keluarkan dan di gunakan. Hampir semua syarikat
yang terlibat pada masa kini memikirkan bagaimana untuk mengurangkan
penggunaan arus elektrik dan memberi keupayaan yang lebih kepada pengguna.

~Kendalian asas sistem penyejukan dan penyamanan udara~

a. Unit peti sejuk domestik
b. Unit penyaman udara tingkap
c. Unit penyaman udara jenis pisah
d. Unit penyaman udara kereta

~Aksesori~
~Pemasangan unit penyaman udara~
a. Unit penyaman udara jenis pisah
b. Unit penyaman udara jenis tingkap

~Mengesan kerosakan dan menservis peralatan penyejukan dan penyamanan udara~
a. Unit peti sejuk domestik
b. Unit penyaman udara tingkap
c. Unit penyaman udara jenis pisah
d. Unit penyaman udara kereta

~Penyenggaraan berjadual unit penyamanan udara~
a. Unit penyaman udara tingkap
b. Unit penyaman udara jenis pisah
c. Unit penyaman udara kereta

~Keusahawanan~
Dalam bidang pembelajaran ini murid diberi pendedahan cara berkomunikasi yang berkesan
dan membuat keputusan. Mereka mempelajari cara menyediakan perancangan perniagaan,
bantuan perniagaan dan pemasaran.
---Kemahiran berkomunikasi
---Kemahiran membuat keputusan
---Rancangan perniagaan
---Agensi yang membantu usahawan
Pemasaran