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He said what?

There are times or will be, when you speak to the representative of an HVAC company and they might as well be speaking a different language. Unfortunately we in the industry tend to tech-speak and not even realize it. Here is some information in English which may help to decipher some of these terms.  Alternatively we would also be happy to help with explanations as well ... if we start doing it again please poke us in the eye…..

Your A-Z guide to air conditioners

Air conditioner: An appliance used for cooling, humidifying, dehumidifying or any other air treatment.

Air flow volume: The amount of air that is circulated through your home or room by the air conditioner. This is usually measured in cubic feet per minute or CFM. This is generally referred to as air circulation. Click on the central air conditioners link to read more about airflow in ductwork.

AFUE: Acronym for Annual Fuel Utilization Efficiency. This is a measurement of the efficiency of a gas furnace. The higher this rating is the more efficient the furnace will be.

Air handler: This is a device that moves and mixes air. They include fan blowers, coils, filters and expansion mechanisms. Generally, the air conditioner unit containing these components is referred to as the air handling unit and will be situated indoors. Click on the split systems link to learn more about air conditioner structure.

ARI: Acronym for the Air Conditioning and Refrigeration Institute

ASHRAE: Acronym for the American Society of Heating, Refrigeration and Air Conditioning Engineers

BTU: British thermal unit. This the measurement used to describe the cooling capacity, or amount of heat removed from the air, of the air conditioner. It is a measurement worked out according to the amount of cooling needed to lower the temperature of one pound of water by one Fahrenheit degree. One ton of cooling is the equivalent of 12,000 Btu’s/h.

Capacity: This refers to the amount of cooling an air conditioner is capable of producing. It is normally measured Btu/h (Btu’s per hour) or in tons.

Charge: Air conditioners do not consume refrigerant, instead it is reused in a continuous cycle. This cycle is contained within a sealed structure. To charge an air conditioner is to add more refrigerant to replace the old and involves recovering the old refrigerant first.

Compressor: This component is responsible for compressing the refrigerant and then pumping around the system. You can read more about this here.

Condensate: This occurs mainly in the evaporator coils when the refrigerant evaporates into a vapor after heat is absorbed from room air. Warm room air is circulated here in order to cool it and it is this change in the temperature that results in vapor condensing into a liquid. To learn more about how air conditioners work click here.

Condenser coil: Tubing made of either copper or aluminum situated in the condenser or outdoor unit. Hot refrigerant gas is pumped through these coils from the condenser; the heat from the gas is dispersed by circulating air over the coils. The heat transfers from refrigerant to air and is released outside. This heat dissipation converts the refrigerant from a gas into a liquid. Go to the ‘How air conditioners work’ page to learn more.

Condenser fan: There are two fans blades in every air conditioner. The condenser fan is for circulating the air over the condenser coils to dissipate the heat from the refrigerant. The other circulates the air over the evaporator coils and back into the room or building. Go to the ‘ Air conditioner parts ’ page to learn more about the different components involved in the functions of your cooling system.

Damper: This is a plate that can be opened or closed to control and balance the airflow throughout the air handler’s ductwork. This control is most obvious in systems with a ‘zoning’ option where cooling can be confined or regulated in individual rooms.

Click on the 'Ductless air conditioners' link to learn more about these systems.

Diffuser: This is a specialized grille with adjustable vents to direct the airflow from the air conditioner into the room. Some models come with a variety of adjustments some of which can distribute airflow in a particular pattern. An example would the ‘shower’ pattern of cool air.

Drain pan: Also known as the condensate pan, this is a pan positioned at the bottom of the air handling unit underneath the evaporator coils. As the name suggests, it collects the condensate that drips from the evaporator coils. This is then drained out through a drainpipe or, as is the case with some portable units, is removed and emptied.

Ductwork: This can basically be described as a large pipe that carries airflow throughout the building both to and from rooms. These can be used for both heating and cooling. Ductwork is commonly made of metal but flexible ductwork, known as mini-duct, is now also available.

Economizer: This is an optional air conditioning accessory that utilizes fresh outside air during cooling requirements in mild weather (below 15 C). A controlled motorized damper simply opening and bringing in outdoor fresh air mixed to 15 C enables the user many benefits to reduce the need for mechanical cooling.

EER: Acronym for Energy Efficiency Ratio. This is a measurement of the efficiency of the cooling unit. It is calculated by comparing the Btu’s to the watts of electricity consumed and the higher the efficiency rating the more efficient the unit. This benefits both environment and consumer as less energy is used which results in a lower operating costs.

Expansion valve: This device controls the temperature and pressure of the refrigerant preventing damage to the compressor.

Evaporator coil: Copper or aluminum tubing situated in the indoor or air handling unit. Liquid refrigerant from the condenser coils is pumped into these coils and evaporates into a vapor as it absorbs heat from warm room air. The air is circulated over the coils by the fan and, once relieved of its excess heat, is pumped back into the room. Click here to read more about other air conditioner parts.

Filter: Material that removes unwanted particles, such as dust and pollen, from the air that passes through it. Click filters to learn more about these.

Fuse: This is a small piece of metal found in all electrical circuits that is designed to melt when a surplus amount of electrical current passes through it. This is preventative measure taken to avoid damage to the other components of the system. They are commonly found in electrical plugs.

Heat exchanger: In air conditioners these are also known as the condenser and evaporator coils. It is where heat moves from a substance or surface with a higher temperature to a cooler temperature.

Heat pump: This is a compression system using refrigerant that can be used for both heating and cooling.

HVAC: Heating, Ventilating and Air Conditioning. This is an example of a system that would use a heat pump.

NEC: Acronym for National Energy Council or National Electric Code used in North America.

NEMA: Acronym for the National Electrical Manufacturing Association.

Package unit: A term to describe an air conditioner system where all the components are contained within one unit. Click on air conditioner unit to learn more.

Refrigerant: This is a liquid with an extremely low boiling point of minus 21.7°F. This gives it unique cooling qualities. Because it responds well to low pressure conditions and condenses easily it is easy to change the temperature of the substance which means it is easy to cool. When it is cooled it absorbs heat quickly and effectively.

Refrigerant charge: This is the amount of refrigerant required by a particular system.

SEER: Acronym for Seasonal Energy Efficiency Ratio. This is the measurement used to rate the efficiency for a cooling system that can also be used for heating (i.e. containing a heat pump. The higher the SEER, the more efficient the system.

Self-contained system: Similar to a package unit where all components are contained within on cabinet. Portable and window air conditioners are examples of such systems.

Split-system: This is an air conditioner that has been split into two units. The outdoor unit contains the condenser and compressor, the indoor unit contains the evaporator coil. Click here to read more on these.

Ton: Another unit used to measure the cooling capacity of an air conditioner. One ton of cooling is equal to 12,000 Btu’s/h.


Central Air Conditioners : How They W

The duct-system central air conditioner explained

Central air conditioners using ductwork normally utilize the ducts in existing air handling systems that have already been built into the house, such as a forced air furnace. They tend to be split systems with the evaporator coil and air handler inside the building and the compressor and condensing unit outside. These are connected by refrigerant tubing and the ductwork circulates the cool air around the building or house. The indoor unit is usually installed in the attic or another small and out-of-the-way space. Many modern central air conditioners are small enough to fit into any number of small spaces, such as closets.

Central air conditioners using a duct system can easily be installed into houses that already use a ducted furnace for heating. This is because the ductwork is already in place and the air conditioner simply uses the existing ducts to circulate the cool air.

Houses that are heated with baseboard heating, radiant heat or steam radiators may not have any existing ductwork. In cases like this ducts would have to be installed along with the central air conditioner making it a very difficult, expensive and in some cases an impossible, job. A more practical solution would be to opt for a ductless or mini-split air conditioner.

The ductless air conditioner system uses tiny refrigerant lines that go through a small three inch hole in the wall which connect the outside condenser unit to the inside air handling unit. These refrigerant lines circulate refrigerant into the house from the outside unit to the indoor air handling units where it used to cool the air. The cooled air is then released into the building while the refrigerant carries the excess heat back to the outside unit for disposal. These systems do require good drainage otherwise condensate may stain concrete and other building materials.

Another option would also be the flexible tubing ductwork known as high-velocity or ‘mini-duct’ air conditioners. These tubes are the pliant equivalent of the more conventional metal ductwork normally used but which only take up about one tenth of the space.

They perform the same functions as the metal ductwork the difference being that they can weave behind walls, ceilings and floors without causing any damage to building materials. It is a far cheaper and less intrusive installation and means central air conditioners can be installed in just about any building, old or new.

Split System Air Conditioner :

Online guide to split-system air conditioners

Split system air conditioner is a term used to describe air conditioners that have been split into an outdoor unit and an indoor unit, in effect separating the hot and cold components of the system which are then connected by refrigerant tubing. The indoor unit typically consists of the evaporator coil and the air handler. This is where the air is cooled and distributed into the required space. The outdoor unit consists of the compressor and condenser where the heat is vented from the building and the refrigerant is cycled back through the system. Split system air conditioners can range in size from large commercial roof top air conditioners to smaller residential systems used to cool the home.

Most central air conditioners use a split system whether it is a ductless system or a system using ductwork to circulate the air throughout the building. The main difference between a split system air conditioner using ductwork and those that don’t, is that the ductless system combines the luxury of whole-house cooling with the convenience of ‘spot cooling’.

With split system air conditioners the indoor unit can be installed into a variety of small crawl spaces, the most popular being the attic or a closet. The outside unit is usually installed in the most convenient and inconspicuous position possible but always ensuring that there is sufficient drainage for the condensate. Where ductless systems are concerned this is usually easier than with those using ductwork as they only require a small hole in the wall and the condenser unit tends to be smaller. These do, however, tend to be more expensive to purchase.

One of the biggest advantages to a split system air conditioner is the significant reduction in noise from the condenser unit simply due to the fact that it is placed outside. They are also significantly more energy efficient in their operation than standard room air conditioners, especially in climates where homes or commercial buildings require a considerable amount of cooling for long summer months.

For drier climates where air cooling and humidification is required, an alternative to the conventional refrigerant based air conditioner would be an evaporative air conditioner. These can come in room-sized units or as a split system air conditioner. They perform the same basic functions of air cooling except water is used instead of a refrigerant. By filtering the air through water-soaked filters, the air is cooled by as much as 20 degrees while at the same time extra moisture is added.

Air Conditioner Parts : Your Online Guide

The principal parts and their functions

There are a number of air conditioner parts whose functions are vital to the performance of the cooling system. Most air conditioner systems include a front cover, filter, thermostat, evaporator coils, selector switch, fan, fan motor, capacitor, compressor, condenser coils and the cabinet or shroud.

Most people will be familiar with the front cover as this is the most visible of all air conditioner parts. These are usually fastened on with a couple of screws and tend to be easy to remove when the air filter needs to be accessed for changing or cleaning.

The thermostat’s main function is the regulation of air temperature. The thermostat has a temperature sensor that reacts to the air temperature by either opening or closing the electrical circuit that controls the air conditioner. This causes the system to switch on or off according to the settings. There are two main types of thermostats: the electromechanical thermostat and the electronic thermostat. Electromechanical thermostats utilize a small glass vial of mercury and a bi-metal strip or coil that reacts to temperature changes by expanding or contracting.

The evaporator coil is the part of the air conditioner that cools the air. These coils do tend to get dirty on the inside after some years of use. You’ll know this has happened if the evaporator coil starts to freeze up and that usually means it needs to be serviced or replaced. The best thing to do in this case is to get a new one directly from the manufacturer. Unfortunately the evaporator and condenser coils are designed to work together and so if one needs replacing, so does the other.

The condenser coil is very similar to the evaporator coil; they are both made of copper or aluminum tubing with fins that lie vertically in relation to the coils. They both contain refrigerant but in the condenser coil this refrigerant is in the form of a hot gas rather than a cold vapor. If these two air conditioner parts are not cleaned regularly then accumulated dirt will affect their ability to dissipate or absorb heat.

The selector switch allows the user to choose the fan speed. While the compressor always runs at the same rate, thereby producing the same capacity of cool air, the fan speed determines how much of that cool air is circulated into the room. If this needs replacing, your best option (and in many cases the only option) is to get a replacement part from the manufacturer.

There are two fan blades in an air conditioner. The one situated in the condenser unit draws fresh air from outside and moves it over the condenser coils to collect heat from the hot refrigerant which is then released outside. The fan blade in the air handling unit draws air from inside the building and blows it over the evaporator coils so that the cold refrigerant can absorb heat from the air. This causes condensation to form on the coils which is collected in a pan at the bottom of the unit. In packaged or unit air conditioners these fan blades would simply be placed on either side of a single fan motor. Fan blades are normally fairly easy to replace but fan motors are so varied that the best place to get a replacement, as with most other air conditioner parts, is to contact the manufacturer of the cooling system in question. To keep fan motors in top condition they should be oiled at least twice every year.

Capacitors can be found in many different electronic devices and are used to store energy in the form of an electrostatic field. If the capacitor should need replacing, two important factors should be noted: the capacitance and the voltage. The air conditioner manual should contain this information, otherwise it can be found on the capacitor unit itself. The shape and size of the capacitor should also be considered for fitting purposes. It is always best to opt for the same or a very similar replacement model to ensure that it works at optimum efficiency. Every precaution should be followed when dealing with these as they can deliver a nasty shock if not fully discharged.

Air Conditioner Compressor : Information and Buying Guide

Your online guide to air conditioner compressors

The air conditioner compressor is the heart of the system because it pumps the refrigerant through the system in a closed cycle in much the same way as the heart pumps blood through the body’s system. The other main function of the air conditioner compressor is to compress low pressure refrigerant gas from the evaporator converting it to a hot, high pressure gas. In doing this the compressor also removes vapor from the evaporator to help maintain a constant temperature.

Scroll air conditioner compressors are favored for their efficiency as they move refrigerant gas along in a continuous flow. This means the system runs smoother, quieter and has less leakage than the other types. This is due mainly to its efficient design which helps it to perform its functions more effectively. It also has some built in mechanisms to help prevent damage to the compressor. The refrigerant is pushed along by air that is compressed between two spiral cogs that fit together in such a way that they form curved gas pockets. One of these cogs is continuously moving around the other in order to drive this air out through the exhaust. Gas is drawn into one of several pockets which become gradually smaller as the cogs move round. This motion compresses the gas which becomes very hot. Once it is sufficiently compressed it is released and moved along to the condenser.

The screw compressor is popular because of its simple design. It usually consists of two intermeshed, screw shaped rotors or spindles that rotate in opposite directions. The refrigerant gas enters the enclosed chamber where it is trapped and compressed between the intermeshed spindles. The opposed rotary directions of these spindles is what causes the gas to move from entrance (suction) to the exit (discharge) where it is moved on to the condenser. This design provides quiet and continuous flow but is not as efficient as the scroll compressor.

Piston, or reciprocating air conditioner compressors, are less popular in residential cooling systems because they are noisier than the other two types. This is because they utilize pistons driven by a motor to compress the gas in a cylindrical-shaped chamber. The gas is taken into the chamber at one end and pistons are pushed in to reduce the amount of space inside. This then compresses the gas which is released through the other end of the chamber and on into the condenser. Aside from being noisy these are not able to supply a smooth and steady flow of refrigerant as effectively as the others are. They are used more frequently in high pressure systems rather than conventional residential air conditioners.

How Air Conditioners Work : Online Guide

How do air conditioners work?

Air conditioners work basically the same way as a refrigerator except that the area it is designed to cool is much larger than your average icebox. It utilizes the unique cooling capabilities of a refrigerant chemical to remove heat from the air.

There are three basic concepts on refrigeration that could help in understanding how an air conditioner works. Firstly, heat always moves from warm to cold. Secondly, the boiling point of a refrigerant will change depending on its pressure. This means that the higher the pressure the higher the boiling point and the lower the pressure the lower the boiling point. And lastly, refrigerant will boil and absorb heat from its surrounding environment when the environment is warmer than the refrigerant. If the surrounding environment is cooler than the refrigerant while it is boiling then it will condense, become a liquid, and lose heat.

Air conditioners work in a cycle which usually begins when the refrigerant is compressed in the compressor causing it to heat up and become a hot, high pressure gas. The heated gas is then moved through a series of coils in the condenser in order to disperse the heat which converts the refrigerant into a liquid.

The liquid refrigerant then goes through to the evaporator coils where it evaporates into a cold vapor. Warm air from inside the building is circulated over these coils and the heat from the air is absorbed by the refrigerant vapor. The newly cooled air is then circulated throughout the building or room and the refrigerant returns to the compressor to begin the cycle again. The evaporator and condenser are also sometimes referred to as heat exchangers.

It is well known that hot air rises, so vents are placed in the ceiling to suck the warm room air into the air conditioner to be taken through to the evaporator coils. This is where it will be cooled by the refrigerant gas then sent back into the room by the fan through vents that are usually placed at floor level.

A thermostat constantly monitors the temperature of the room or building. Once the required temperature has been reached it will turn the air conditioner off. When the temperature begins to rise again, the thermostat will turn the air conditioner back on. Most air conditioners, such as central air conditioners and many room air conditioners, have this option.

Room air conditioners work in the same way as a central system but are far more compact with the entire cycle taking place in a single unit placed in the room. Split system air conditioners also work in the same way, but are divided into two units. The air handling unit inside the building contains the evaporator coil and the unit containing the condenser and compressor is placed outside. They are connected via refrigeration pipes and utilize ductwork or tubing to circulate air throughout the system and the chosen area.

Ductless Air Conditioner Systems : Guide to Mini-Splits

The online guide to ductless air conditioners

Ductless air conditioners, or mini-splits, are very similar in design to central air conditioners that use ducts as they also consist of two units, one outside containing the compressor and condenser, and one inside containing the evaporator and fan. The inside unit is usually mounted on the wall or on the ceiling, the difference between the two models is that ductless systems are generally smaller and quieter and, of course, they don’t require any ductwork.

Ductless air conditioners are ideal for buildings that have no built in ductwork such as homes that have baseboard or radiant heating and old buildings where installing ducts would be not be practical or feasible. They are also commonly used for home extensions where the house already has a central system in place but extending the ductwork is impractical.

There are a number of advantages to the ductless air conditioner, not the least of which is that you can buy the system in small portions. You could buy a unit for each ‘zone’ or area of your house separately and eventually end up with a full central system. This is because the outside unit can control between one and four indoor units at a time. They are easy to install too; all that is needed is a three inch hole in the wall for the refrigerant lines and wiring.

The biggest advantage to ductless air conditioners is that they combine the cooling capacity and efficiency of a central system with the ‘spot cooling’ capabilities of a room air conditioner unit. This gives you more control over your cooling system enabling you to cool specific rooms according to your requirements. This is a particularly appealing notion for many as it is a feature that can be utilized to further increase the efficiency on an already energy efficient product. This in turn means lower electric bills, which is always a plus.

Conversely, the biggest disadvantage to ductless air conditioners is how much they cost. They do tend to be fairly expensive to buy, approximately 30% more than conventional central air conditioners and about twice as much as a room air conditioner. However, if you do require a central cooling system in a building without ducts then this may still be a far cheaper option than attempting to install ductwork.

Portable Air Conditioners : Convenient Cooling Systems USA

Online guide to the portable air conditioner

Portable air conditioners have the obvious advantage of being compact enough to be moved around from one location to another with very little effort and without the hassle of complicated installation. These small units usually come on wheels and can simply be plugged into the nearest socket. Very easy and very convenient.

The biggest disadvantage to this unit is that you will need to provide some sort of water supply. They can be filled manually but most units come with a hose that can be fitted onto an outside faucet. Evaporative coolers can use anything from three to fifteen gallons of water a day and do need to have access to outside air. At least one window needs to be open during use which means these will not be effective in extremely hot weather.

The second and more commonly used type of portable air conditioner uses the same methods of cooling as all standard room units, refrigerant. The refrigerant is cooled in a condenser and is then pumped through an evaporator coil. The air which is circulated around this coil is then cooled by the refrigerant inside and is pumped out into the room. The heat is discarded out the window through a vent.

There are two main characteristics that make portable air conditioners so flexible. These are the vent and the draining system. The vent is installed through a window and the condensate is either collected in an internal tray (that needs to be emptied at least once a week) or is pumped out the window from a hose along with the vented heat.

Portable air conditioners are one of the industries later additions to residential cooling systems and are only suitable for ‘spot cooling’. They can be effective in cooling one room but like window air conditioners they are usually best used as a support to existing central systems during periods of extreme heat. Some portable units can be easily adapted for use in cars, boats and recreational vehicles such as camper vans.

Duct Systems : Guide to Duct Air Conditioners

The online air conditioner guide

Duct system air conditioners usually use ducts that are already in place within a home or office building. These systems tend to be split with a condensing unit and compressor outside the building and an interior evaporator coil and air handler.

Most people will have seen ductwork in films as the square-shaped, metallic tunnels used as an escape route out of a building. The standard size is usually approximately eight inches tall and eighteen inches wide, but it is always determined by the amount of friction caused by the moving air in opposition to the duct itself.

The speed at which air flows through this ductwork is what determines the amount of noise it makes and any bends or turns must be smooth and rounded to avoid changes to this speed. Central air conditioners using ductwork are generally known as low velocity systems. This refers to the speed at which the air travels through the ductwork and is measured in cubic feet per minute (CFM).

Air Conditioner Filters : User Guide

The functions of an air conditioner filter explained

Air conditioner filters trap small particles in the air and prevent them from entering a house or commercial building. These are usually effective in trapping airborne particles such as pollen, plant spores, dust, bacteria and even some airborne viruses. They are also effective against odors such as those from cooking, pet smells and tobacco. Air conditioner filters are very important in the overall functioning of the system because keeping the air flowing through it clean ensures that it runs more efficiently. If air conditioner filters are not properly cleaned they can become clogged and the excess buildup of dirt will cause extra resistance to the air flow. This could result in damage to other air handling devices and functions, such as ventilation, and the air conditioner could become damaged as a result.

There are four key types of air filters: electrostatic filters, electronic filters, disposable fiberglass filters and permanent mesh filters.

For cleaning, the filter needs to be removed from the air conditioner and sprayed thoroughly with water. You need to spray in the opposite direction to that at which the air would normally flow. There are usually arrows to indicate this on the frame of the filter. Once you’ve dislodged the dirt spray the filter down on the other side to free any remaining dirt. It is a good idea to get some cleaner to spray on in order to remove any stubborn stains and dirt and then give the filter another rinse. Once it has drip dried it can be reinstalled. You can usually get cleaner from the manufacturer.

Electronic air conditioner filters work in the same way as the electrostatic filters, but they use an electric charge to produce the magnetism that attracts the particles. These types of filters can be just as effective as the electrostatic filters but are not as energy efficient. This is because they use power from the mains, meaning that the air conditioner would use up more electricity resulting in higher electric bills.

The disposable fiberglass filters are the least efficient as they consist of meshed fiberglass and can only trap large particles. They are fairly cheap but do need to be changed regularly as they can become clogged with large dust particles and this would further reduce their efficiency.

Permanent mesh filters are more specific in what type of particles they trap. This is because they come in a wide range of different materials which determine what the filter is capable of trapping in its fibers. These are a good option for anyone suffering any particular allergies, hay fever for example; as a filter specifically designed to segregate pollen could be used. This type of air conditioner filter can be cleaned using water and, once dry, can be reused. Although it is a good idea to have it replaced with a new filter on a regular basis because wear and tear will eventually affect its efficiency.

Air Conditioner Unit Information

The online guide to unit air conditioners

Unit air conditioners are cooling units that are designed to cool only one room or a single space. These units come in various sizes developed for cooling a wide variety of different sized rooms, so choosing the right one is essential for it to function efficiently and effectively. The cooling capacity in unit air conditioners can range from 5,000 to 30,000 BTUs/hr.

The window and casement air conditioners are fundamentally the same thing, the only difference being the sort of window they can be installed into. A window air conditioner will fit into most standard windows that slide up and down. The casement unit is designed to fit into narrower windows that open outwards or windows that slide open, to the left or right. They do tend to be fairly cheap which makes these an ideal choice if you don’t want to spend too much on installing a permanent unit air conditioner when you’ll only be needing it for a short period during the hottest summer months. This is mainly because they are easy to install and shouldn’t require the help of a contractor. The only exception with this air conditioner unit is that in some situations you may need to remove a window panel to install it. This may mean spending a little more, but certainly not as much as the installation of a wall unit.

Portable air conditioners are the cheapest of the unit air conditioners as they don’t require any installation, all you need is a window for the vent. These are freestanding air conditioners, usually on wheels or coasters, making them easy to move from room to room. They would certainly be the best option for those on a tight budget. They serve well as an extra support for an existing central system during the most extreme summer months. They can be moved around according to where you may require the extra cooling. These could also save you from high utility bills as you can use it only where it is needed instead of cooling the whole house, for example, at night when you may only need the cooling in the bedroom. They are also ideal for those living in less extreme climates where cooling is only required for a short duration in the warmer summer months.

A wall unit is built into the wall and requires a sleeve with which to secure it (usually sold separately by the manufacturer). Wall units perform the same functions as the window units but come in bigger sizes and tend to be a more permanent fixture. They will need their own power line whilst in use and can be fairly expensive, mainly due to the high installation costs. This is because a contractor will need to be brought in to correctly install the unit through the wall, ensuring all safety precautions are taken. For this reason wall air conditioners are best suited to those who require a fair amount of cooling but may not be able to afford a central air conditioner.

For homes and larger commercial buildings situated in an area with a dry and arid climate, a good alternative is the evaporative cooling system. These can come in many sizes from portable units to bigger systems that utilize large cooling towers positioned outside the building. These cooling systems use water pumped through a system of pipes leading to any number of room cooling units to cool the air. The air is passed through water soaked filters which serves to cool it whilst at the same time adding moisture.

Window Air Conditioners : Cooling Unit Guide

Online guide to the window air conditioner

Window air conditioners are self contained units that are designed to fit into a standard window that slides up or down. These are fairly low-cost room air conditioners that are easy to install as all you need is a window and an electric plug; no additional wiring is required and most units will simply slide into the window. The only real disadvantage is that they can be a little drafty and so may need to be removed during winter. Some window air conditioners double as heaters but these tend to be slightly more expensive.

If the area to be cooled is of small or medium size then a window unit should be enough to keep the temperature and humidity levels down. It would also be far more cost effective than a central air conditioner as it would be cheaper to purchase and cheaper to operate in the long run.

It is, however, important that the unit is the correct size for the space that it will be required to cool. If it is too big it will continuously be shutting on and off as it will cool the room too quickly. This will use up a lot of energy meaning higher than necessary electric bills. It also means that the air conditioner will not be able to dehumidify the air in the room effectively leaving it cold and clammy. If the window unit is too small it will run continuously without properly cooling the room. For these reasons, having the correct measurements at hand when buying your unit is crucial.

Measuring the window is also important because you need to ensure the air conditioner you purchase will fit into the window space. If it is too small it will let in too much warm air from outside and if it’s too big it simply won’t fit. So make sure you measure the window correctly, possibly more than once, so you are absolutely sure of the measurements before you purchase your window air conditioner.

Roof Top Air Conditioners : External Cooling Units

Online guide to the roof-top air conditioner

Roof top air conditioners cool more than half of America’s small commercial buildings, from schools and retail stores to hospitals, restaurants and office buildings. They range from 65,000 to 135,000 BTUs/hr of cooling capacity and are usually split system central air conditioners providing cooling through ductwork. The outdoor unit consists of the compressor and the condenser and is installed onto the rooftop. This is due to a number of reasons, most notably because of the large amount of space on the roof, but also because it is well out of the way and doesn’t cause unattractive obstructions to the building.

Roof-top air conditioners can also come as a packaged unit where all the mechanics are enclosed in one unit. These tend to be used for larger commercial buildings where the distance between the indoor air handling units and outdoor cooling units is too great causing problems with lubrication in the ductwork and making it unmanageable. These are usually known as chilled water systems.

This type of roof top air conditioner uses refrigerant to cool the water which is then pumped throughout the building via ducts and on to the air handling units. This cooled water is then used to chill the air as needed. There is no limit on the length of ductwork on these systems as there is no issue with lubrication all that is required is that they are sufficiently insulated. These types of roof top air conditioners would also be ideal for use in arid climates as the water would add moisture to the air as it cools.

Roof top air conditioners are central systems that are used to cool entire buildings but the main problem with their position on the roof is that they are exposed to direct sunlight. This means they can get very hot during the day which reduces efficiency. Wherever possible these units should be installed in an area that gets the least sunlight, especially during mid-day.

Many roof top air conditioners in use today are not as energy efficient as they could be simply because many buyers opt for the cheaper units without realizing that the cost of operating a lower efficiency model will be more expensive in the long run. More expensive variations that meet Energy Star standards may be more expensive to purchase but will almost certainly be more cost effective in the long term.

Many commercial buildings, such as those mentioned above, will have built-in ductwork as part of a ventilation or heating system, whilst others will have been built with an air conditioner system in mind. Some older buildings may not have been built with any ductwork included. In some cases it would still be possible to install a central air conditioner with a mini-duct or mini-split system. These systems have been designed specially for buildings where installing ducts would be impossible.

Room Air Conditioners : Types of Air Con Units

Online guide to the choosing the right room air conditioner

If you are looking for an air conditioner to cool a particular room, there are a number of options open to you. There are a number of different types of unit air conditioners such as the window, casement, portable and wall air conditioners all of which perform the same functions. Choosing the most suitable of these depends on your cooling requirements, budget and personal preference.

Below we have included an introduction to each of the five most popular varieties of room air conditioners; a fuller explanation of each can also be found within this section (simply click on the appropriate link).


Casement air conditioners tend to be a little more expensive than the standard window unit as they may require the removal of a window panel for installation. Most of these units can simply be plugged in and don’t require any extra electrical wiring.


There are two kinds of portable air conditioners. The first is what is known as an evaporative cooler which uses water to cool the air. The air is brought in from outside and passes through wet pads which also act as air filters. The air is cooled by as much as twenty degrees and the water-based filter means that the air entering the room will have an increased amount of moisture. This system is good for dry climates as more humidity is added to the dry air.


Window units are useful for cooling office spaces and can provide more cooling support for a central system during extreme weather. This may be of particular importance for use in computer rooms or any room that may be especially susceptible to heat.

Casement Air Conditioners : Information on Window Units

Online guide to the casement air conditioner

Casement air conditioners are essentially window units but are designed for narrower windows that swing outwards or slide across rather than those that slide up and down. These units are sometimes also known as a slider air conditioner. They are self contained units, or packed terminal units, as all the mechanisms are contained within one large compartment.

The obvious advantages to casement air conditioners are that they are low cost, do not require additional electrical wiring and are easy to install. The downside is that they may need to be removed during winter as they can occasionally get a little drafty. There are some casement cooling units that can provide additional heating but you may need to spend a bit more for these. If you only have one space to cool it would be far more beneficial to get a casement or unit air conditioner as they are cheaper than a central air conditioner both to buy and to run.

Casement units are only suitable for cooling one room and you do need to ensure that the size of the unit is sufficient for the size of the room. If the unit is too big it will cool the room too quickly and it will switch on and off constantly, using up more energy than is necessary. Not only will this be more expensive to operate but it will also cause the air in the room to feel clammy and damp as the air conditioner will not be able to effectively remove excess humidity. If the unit is too small it will simply run all the time without sufficiently cooling the room. You need to measure both the window and the room in order to determine what size you need and to ensure the casement air conditioner you select will fit into the chosen window.

These units are also good if you need additional cooling support for a central system in one room of the house, such as computer room, but they would not be the most cost effective or practical way of cooling an entire house or building.


The use of the www.mandtac.com web site is intended as a simple tool to obtain advice with regards to air conditioning systems and units.

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