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An air conditioner is basically a refrigerator without the insulated box. An air conditioner is doing exactly the same thing as your fridge, except it dumps the heat it takes out of the controlled area and dumps it outdoors instead of in your kitchen. To understand what goes on in the system, let's start where the "freon" gas enters the compressor located typically in the outside part of the unit.
As the Refrigerant gas enters the compressor, it squeezes this freon gas that has just absorbed heat from the indoor air, causing it to become extremely hot. This is just like what happens near the end of a bicycle pump when you push the handle down. The air being compressed into the end of the pump will get hot, because all the heat that the air inside it contained, is squeezed into an area that is many times smaller than where it just was. This now high-pressure freon gas, that is now many times hotter than it was before it got squeezed, runs through a set of coils outside where a fan blows on it to cool the high temperature gas, so that a large portion of this concentrated heat is removed from it. The fan and coil arrangement outside are very similar to a radiator on a car.
As the Outside unit (or radiator) cools this hot vapor, it condenses into a liquid just like steam condenses into water when it loses its heat. This high pressure freon liquid which has now had a lot of its original heat forced out of it, is then pulled back into the house where it waits its turn to pass through a tiny opening that is the entrance to the indoor coil that sits within your home's air stream.
By using this tiny opening to "back-up" the pressure on the outdoor part of the system, it allows the compressor to maintain a low pressure side within the indoor coil that is in your home's air stream. When the cooled High pressure gas finally passes into this low pressure area, the difference in pressure causes part of it to immediately expand into a gas. In a sense, this is like the compressor working in reverse, because now the cool freon is occupying a bigger area, so the heat that was left in it now has to spread itself out over its bigger size.
This need to use its limited heat over a now bigger gas molecule, causes it to rapidly become quite cold, so that as it passes through the indoor coil, the air passing over this coil (the radiator effect again) is cooled and then spread through your home by your home's duct work. Meanwhile the heat that was taken out of your home's air, has entered the warming freon gas so that when it gets back to the compressor the whole process is repeated.
In cooling mode, a fan draws warm air from inside through a filtration system and over the evaporator coil. As the air passes over the coil, any moisture in the air condenses on the evaporator coil and then runs off into a drip tray where it is drained away. The refrigerant in the evaporator coil enters as a liquid and as the filtered air passes over the cold coil, it reduces the air temperature. The refrigerant then carries the warm air in a gaseous state to a compressor where the vapour is compressed and passed through to the condenser coil. A fan then moves air across the warm refrigerant and expels the warm air outside while reducing the temperature of the refrigerant. As the refrigerant cools down, it changes back to its liquid state and is pushed back to the evaporator coil to repeat the process.
Air Handler The air handler functions as the evaporator section of the air conditioning system. The air handler is typically located indoors and its primary purpose is to circulate the conditioned air.
BTU - British Thermal Units 1 BTU = amount of heat required to increase the temperature of 1 pound (0.45kg) of water by 1 degree Fahrenheit (0.56 degrees Celsius).
Compressor The compressor is the motor which drives the condensing unit.
Condensing Unit The condensing unit acts as a pump which compresses the vaporised refrigerant from the air handling unit, liquifies the gas and returns it to the air handler.
Evaporator Coil The evaporator is located inside the air handler unit and is where the refrigerant vaporises and absorbs heat.
The refrigerant is a substance which absorbs heat by changing states from liquid to gas (evaporating). It then releases the heat by changing back to its liquid state (condensing).
SEER - Seasonal Energy Efficiency Rating The SEER of an air conditioning unit tells you how efficiently the unit uses electricity. The higher the SEER rating, the greater the efficiency. This can be calculated by dividing its BTU rating by the unit's wattage. For example, an 11,500 BTU air conditioner that consumes 1,200 watts will have a SEER of approximately 9.5 (11,500 BTU / 1,200 watts).
Split System. A split system air conditioner allows the air handler to be installed away from the condenser. This allows more flexibility in confined spaces and also helps reduce indoor noise by having the condenser located outside.
Thermostat The thermostat is a temperature-sensitive switch that controls the heating and cooling system. If the temperature varies from a predefined setting, the thermostat turns the air conditioner on to restore the temperature to the desired level.
Air conditioning includes the cooling and heating of air. It also cleans the air and controls the moisture level. An air conditioner is able to cool a building because it removes heat from the indoor air and transfers it outdoors. A chemical refrigerant in the system absorbs the unwanted heat and pumps it through a system of piping to the outside coil. The fan, located in the outside unit, blows outside air over the hot coil, transferring heat from the refrigerant to the outdoor air. Most air conditioning systems have five mechanical components: A compressor, A condenser coil and fan A metering device or an expansion valve, An evaporator coil and blower. A chemical refrigerant
Most central air conditioning units operate by means of a split system. That is, they consist of a "hot" side, or the condensing unit—including the condensing coil, the compressor and the fan—which is situated outside your home, and a "cold" side that is located inside your home. The cold side consists of an expansion valve and a cold coil, and it is usually part of your furnace or some type of air handler. The furnace blows air through an evaporator coil, which cools the air. Then this cool air is routed throughout your home by means of a series of air ducts. A window unit operates on the same principal, the only difference being that both the hot side and the cold side are located within the same housing unit.
The compressor (which is controlled by the thermostat) is the "heart" of the system. The compressor acts as the pump, causing the refrigerant to flow through the system. Its job is to draw in a low-pressure, low-temperature, refrigerant in a gaseous state and by compressing this gas, raise the pressure and temperature of the refrigerant. This high-pressure, high-temperature gas then flows to the condenser coil.
The condenser coil is a series of piping with a fan that draws outside air across the coil. As the refrigerant passes through the condenser coil and the cooler outside air passes across the coil, the air absorbs heat from the refrigerant which causes the refrigerant to condense from a gas to a liquid state. The high-pressure, high-temperature liquid then reaches the expansion valve.
The expansion valve is the "brain" of the system. By sensing the temperature of the evaporator, or cooling coil, it allows liquid to pass through a very small orifice, which causes the refrigerant to expand to a low-pressure, low-temperature gas. This "cold" refrigerant flows to the evaporator.
The evaporator coil is a series of piping connected to a furnace or air handler
that blows indoor air across it, causing the coil to absorb heat from the air.
The cooled air is then delivered to the house through ducting. The refrigerant
then flows back to the compressor where the cycle starts over again.
Welcome to Icecape Limited t/a RAC Kettering A leading and progressive supplier and installer of air conditioning systems at the most competitive prices available. RAC is at the forefront of supplying, installing and maintaining a range of state-of-the-art, high quality and reliable air conditioning systems into the commercial, industrial and domestic sectors.
We provide cooling and heating solutions for BARS, PUBS, CLUBS & RESTAURANTS; SHOPS, OFFICES, WAREHOUSE & FACTORY UNITS; HOSPITALS & SURGERIES; MOBILE HOMES as well as HOUSES, BUNGALOWS AND CONSERVATORIES.
Please browse through our website so that you can fully appreciate the benefits that RAC Kettering can bring to you from a wide selection of advanced technology air conditioning systems to suit your needs and requirements.
Air Conditioning is a process of what we call Heat Transfer. Regardless
of the outdoor conditions we are able to draw on the natural hot or cold molecules
in the atmosphere and use them to heat or cool an indoor air space.
An Air conditioner removes cold molecules from the air outside passes them through pipe work into your house, office or conservatory and then releases them. At the same time it removes the heat from indoors and releases it to the atmosphere outside. By reversing this process we can also heat a house, office or conservatory.
All models, excluding Portables, come with an Inside Unit and an Outside Unit, providing high-efficiency rotary compressors that guarantee refrigerant compression with minimal loss, or a heating efficiency of nearly 300% for each 1kW input giving up to 2.85kW output. So what does all that mean - simply put, it means that the cost control over your interior climatic environment is significantly enhanced in your favour.
Too often, precision air conditioning is only considered when humidity
control is required. If the application does not demand humidity control, comfort
cooling is installed. In fact, the combination of recent economic conditions
and an increasingly competitive market have led to a rise in the number of server
rooms and data closets being served by traditional comfort cooling. These applications
can be air-cooled with a traditional, residential-style split system, or utilize
a cooling only water-source heat pump or a chilled water fan coil unit. These
systems appear attractive to the installer because of their apparent low up-front
costs. However, with some analysis, the cost differences between precision and
comfort cooling systems are not what they first appear. General Applications
ConsiderationsSensible Cooling CapacityThe first thing to consider when comparing
costs of cooling units is the amount of sensible cooling available. Since almost
all of the loads in these rooms are sensible heat, units should be selected
on their sen-sible capacities. The higher latent capacity of comfort units actually
hurts their perfor-mance in this application by unnecessarily lowering the humidity
in the room. In addition, comfort cooling units are usu-ally rated at the ARI
standard of 80 degrees F entering air temperature not nearly cool enough
for computers and servers. One comfort manufacturers two-ton unit actually
de-rates to one ton of sensible cooling when adjusted for a 72 degrees F entering
air temperature. Be sure to compare the cost of units with the same sensible
capacity at the same entering conditions and not just two-ton versus two-ton.
A lower tonnage precision air conditioning system will probably match the higher
tonnage comfort unit for most applications.AccessSmall precision ceiling units,
which are designed for one-side only service access and filter replacement,
utilize tight room space more efficiently. Several comfort cooling units require
multi-side access, which restricts where they can be installed and can increase
ducting requirements and cost. One comfort unit actually requires bottom access,
making installation of the code-mandated auxiliary drain pan virtually impossible.Condensate
Pump Power, Drains and Alarms Because of limited above-ceiling space, many small
units require condensate pumps. condensate pumps get their power from
the unit and do not require an additional power feed. Most comfort units require
an additional electrical feed (usually at a different voltage) for the pump,
increas-ing overall installed cost. Also, if a condensate pump detects
an overflow, it shuts off the unit and sends an alarm to the wall-mounted controller.
The comfort cooling pump sends its alarm by overflowing water onto the floor.
Be sure to compare the cost of units at the same sensible capacity at the same
entering conditions . . .
(If the pump is installed in the auxiliary pan with an overflow switch, it will shut the unit down; however, the owner will not know the unit is off until the room gets hot.) Finally, since units are internally trapped, the required number of field solder joints is reduced, further saving cost. Some comfort units actually have more than one required drain connection, adding addi-tional labor cost.Remote shutdown Many small server rooms have either an FM200 fire suppression system or an Emer-gency Power Off (EPO) system. Both of these require the air conditioning unit to be shut down immediately upon alarm. Units come standard with remote shutdown contacts. Comfort units must be specially wired to accomplish this task, increasing the owners cost.MonitoringUsually, smaller rooms are not continuously occupied. Notification of a problem with the unit is very important. Units come standard with a common alarm con-tact which can be connected to a variety of alarm or management systems. Since this contact picks up all alarms within the unit, not just temperature, potential problems (such as a dirty filter or clogged condensate line) can be found and fixed prior to the room getting out of control. Continuous Operation and Filtration evaporator fan motors are designed to run continuously to help eliminate hot spots in rooms and provide for increased filtration. Ducted units have 4-inch pleated filters as standard. Even though their fans can be put in the on position, comfort cooling units are designed for intermittent operation and typically do not have the required motors for continuous duty. Typi-cal comfort cooling filters are 1-inch throw-away, which can catch large contaminants, but are not very effective in controlling dust.Air-Cooled Application ConsiderationsLow ambient controls. Small systems come standard with low ambient controls to -20 degrees F. This is important since the room will likely require air conditioning regardless of out-door conditions. Low ambient controls must be added to comfort cooling systems at an increased cost and generally are rated only down to 0 degrees F or 20 degrees F. Often this option requires field installation, raising costs even further.Voltage RangeSince many air-cooled comfort units are actually residential units, they are designed around a nominal input voltage of 240 Volts. However, in a commercial building, this voltage usually comes from a three-phase panel, making the actual input volt-age nominally 208V. This voltage is very close to being out of range for some of these units. Comfort cooling units are designed for intermittent operation and typically do not have the required motors for continuous duty.
4One manufacturer lists their minimum volt-age as 207 volts. s small systems are rated at 208/230 to cover the entire range of possible commercial voltages. Water Cooled Application Considerations. units come standard with a variety of water-regulating valves pre-installed at the factory. Specifically, two or three-way valves are available in standard and high pressure ratings to suit numerous applica-tions. Comfort cooling units require the purchase and installation of an external valve, adding material and labor cost.Compressorized Application ConsiderationsHot gas bypassBecause of load uncertainty or future growth, hot gas bypass is a frequent addition to a small unit. It is standard on every compressorized Mini-Mate2. Providing hot gas bypass extends the compressor life by reducing the number of compressor cycles if the load of the room does not match the unit capacity. This is often the case when simple room load esti-mates have been made (or when room equipment loads are not operating at full capacity). Another benefit is enhanced humidity con-trol. As offered with some microprocessor controls, hot gas bypass reduces the latent (or dehumidification) capacity of the Mini-Mate2 coil, thus allowing more of the water vapor to stay in the space. Hot gas bypass warms the evaporator coil and is an effective means to dry the coil. Yet, during a call for dehumidification, some controls will disable the hot gas bypass mode, thus providing maximum latent removal.Chilled Water Application ConsiderationsControl Valves and Controlssome units come standard with a variety of control valves, including high pressure, pre-installed at the factory. Comfort cool-ing units do not. Also, since the thermostat and control valve must be purchased sepa-rately, these items must be designed and integrated in the field, likely adding relays and wiring. This not only adds field cost, but increases project management time as sep-arate orders must be placed and shipments tracked.Starters and Motor Mountingsome units do not require external start-ers. Most chilled water units require exter-nal starters, adding material and labor cost. Also, many chilled water units have the motor shipped loose which adds field labor time.ConclusionPrecision air conditioning systems are designed specifically to cool electronic equipment. Their high sensible heat ratio and continuous-duty design makes them ideal for small computer rooms and closets. They also include a number of features that simplify and reduce installation cost. Consequently, precision cooling units are almost always a more effective and cost efficient choice.Precision air condition-ing systems, such as the Mini-Mate2, are designed specifically to cool electronic equip-ment. Their high sen-sible heat ratio and continuous-duty design makes them the best choice for small com-puter rooms and closets.