Air Conditioning :- For human comfort we need air conditioning system. Air conditioning means not only to mainatain room's temperature but to condition the air as well. Means in air conditioning we maintain comfortable temperature, air purification, control humidity, control odours and maintain level of oxygen by ventilation. Air conditioners are designed to maintain a temprature not below than 16 degree celcius. But human comfort level according to ASHRAE is from 20-24 degree celcius. An air conditioner should not run at temperature below this limit to protect human body's health.
Condenser
Choosing an air conditioner is a bit cofusing thing for the people who don't have any idea about air conditioning systems. In this article I will share a very useful information which will help anyone to choose best air conditioner according to their place.
1.1.1. Split Air conditioner :- Splti air conditioner consists of two parts one is indoor unit and other is outdoor unit. Indoor unit is hanged on the wall of a room and outdoor is placed or fixed outside the conditoned space. Split air conditioner consumes more power and electricity bills can empty your pocket. Because of long pipe runs cycle of refrigeration system becomes longer and it increases the load on compressor. Split air conditioner has less longer life and chances of leakage of gas are also high because of more joints in copper pipe at the time of installation. Split air conditioner is good for office area as it does not create sound. High installation and maintenance cost.
A split air conditioner may be ductable as shown in figure below, means through ducting network air can be distributed to different areas for air conditioning purpose.
Installation process-
1.1. Distance between outdoor and indoor unit connecting copper pipes should not be more than recommended in my opinion not more that 5 meters.
1.2. Indoor unit should be fixed on the wall at a height not more than 5feet 6inch and it should be in the exact center of the wall horizontally.
1.3. Drain pipe should not be droped to an open area without U-trap and use 1inch dia pipes for drain.
1.4. Outdoor unit should not be placed on the roof directly exposed to sun. If possible choose north wall for the hanging of outdoor unit as effect of sunshine in this direction is less as compared to other directions.
1.5. Out door unit should be hanged considering ease in maintenance for the technician.
1.6. For outdoor units there should not be any wall or obstruction near it to a distance of 3 meter in each direction.
1.1.2. Window Air conditioner :- A window air conditioner consists all components in a single unit. All the required accessories and equipments are fixed in a single body. Window air conditioner are more effecient as the gas cycle is small because no separate outdoor unit is used and no extra copper piping runs. These units dont need any copper joints as the product is completely ready to use by the manufacturer. These units are a good choice for homes. Low installation cost and maintence cost.
Installation Process :-
2.1. Installation of window air conditioner is very simple as compared to split air conditioner system. Try to fix it in the window in the north direction.
2.2. It can be placed at a height of not more than 5.5 feet.
2.3. It can only be installed in a window because condenser side is always kept outside to release the heat in atmosphere. If its kept inside a room it will produce heating and cooling in same amount and after some time it will stop working because of less air circulation arround the condenser.
2.4. Window air conditioner should be installed in a window in such a way that no gap remain between AC body and window. It should be properly air sealed so that cooling lose may not happen.
5 star rating window AC are best selection low power consumption.
1.1.3. Cassette air conditioner :- A cassette air conditoner is much similar to wall split air conditioner but indoor unit is totally different in shape and its function. A cassette air conditioner indoor unit can be hanged on ceiling using proper anchor fastners and threaded rods as shown in figure below. Indoor units can through air through a horizontal blower in two or four way directions as per requirement and return air is sucked from center grills to maintain air circulation and air conditioning effect as shown in figure below. This type of air conditioner is very quite and are very power efficient. The copper piping system is designed to work with refrigerant gas or chilled water too.
1.1.4. VRF/VRV (VARIABLE REFRIGERANT FLOW/VARIABLE REFRIGERANT VOLUME) :-
Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented by Daikin in 1982. Like ductless mini-splits, VRFs use refrigerant as the cooling and heating medium. This refrigerant is conditioned by a single outdoor condensing unit, and is circulated within the building to multiple indoor units.
VRFs are typically installed with an Air conditioner inverter which adds a DC inverter to the compressor in order to support variable motor speed and thus variable refrigerant flow rather than simply perform on/off operation. By operating at varying speeds, VRF units work only at the needed rate allowing for substantial energy savings at partial-load conditions. Heat recovery VRF technology allows individual indoor units to heat or cool as required, while the compressor load benefits from the internal heat recovery. Energy savings of up to 55% are predicted over comparable unitary equipment. This also results in greater control of the building's interior temperature by the building's occupants.
Working principle & Block diagram for various types of VRF/VRV system: There are various types of VRF system used for split air conditioning system.
1. Only Cooling type VRF system
2. Heat Pump VRF system (2 pipe system)
3. Heat Recovery VRF system (3 pipes system)
4. Hybrid VRF system
1. Only Cooling type VRF system
Air conditioning and refrigeration has same cycle and four components and same cycle to produce cooling effect. But main difference between them is, air conditioning is done for human comfort and refrigeration is done to increase the life of eatable products.
There are four main components of refrigeration or air conditioner.
1. Compressor
2. Condenser
3. Expansion valve or capillary tube
4. Evaporator
Compressor is called heart of refrigeration cycle. Compressor has two ports one is for suction and other is for discharge. Compressor discharge the refrigerant to condenser (outdoor unit ) at a high pressure and high temperature. At this stage the refrigerant gas is in vapor form and when it starts to pass through the condenser it looses its temperature and comes in liquid form but pressure remains the same. After passing through the condenser refrigerant starts to pass through the expansion valve or capillary tube. Here is the hidden truth. This is the basic principle of gases that if gases are expanded in vaccum they loos temperature, same principle applies in air conditioning and Refrigeration. The expansion valve has very small dia through which refrigerant with high pressure tries to pass but because of tiny space it tends to loose its velocity and suction pressure of compressor start expanding this refrigerant due to which refrigerant's temperature goes down and cooling effect is produced. When this referigerant with low pressure and low temperature passes through the evaporator (indoor unit like split ac) it again gain the heat and space gets cool due to blower which is circulating room's air on its coils. If humidity level (moisture) is high in air, cooling and dehumidification process is performed by air conditioner. When room's air is circulated over the cooling coil of evaporator (indoor unit) humidity content starts to condense over the coils and start to flow through drain pipe in the form of water. This process in called cooling and dehumidification, so there is no separate humidifier installed in air conditioner.
Compressor
Expansion valve:- An expansion valve is used in refrigeration or air conditioning cycle to control the refrigerant flow. To produce cooling effect in evaporator it is necessary to drop the pressure of refrigerant coming from the condenser with low temperature but high pressure. When refrigerant passes through the small dia of expansion valve or capillary tube its pressure drops and suction pressure from compressor makes the refrigerant gas to expand. This expansion causes the cooling effect in the evaporator.
After passing through the expansion valve the refrigerant with low pressure and low temperature passes throught the evaporator. Where evaporation of refrigerant happens and cooling effect is produced in the conditioned space. As the refrigerant in the evaporator starts to boil and is converted into vapor form. Evaporator is known as cooling coil as well in indoor unit. Evaporator and condenser work same like an heat exchanger and are same in construction with combination of copper tubes and fins, but produce different effects.
Before filling the refrigerant with refrigerant vaccum inside the copper tube circuit is created so that expansion of refrigerant could take place.
This is how an air conditioner works.
There are different types of air conditioning systems -
1. DX Units :- DX stands for direct expansion means the type of an air conditioner in which air directly falls on the cooling coil and refrigerant in the cooling coil starts to evaporate. Most commonly air conditioners for home or offices are DX units like window air conditioner, split air conditoner, cassette air conditoner, VRF/VRV air conditioners or any other system in which air directly takes cooling effect from cooling coils.
2. Central air conditioning system:- Central air conditioning system is the system where water is used to transfer cooling effect from source to conditioned space like chillers.
1.1. Types of DX Units:-
1.1.1. Split Air conditioner :- Splti air conditioner consists of two parts one is indoor unit and other is outdoor unit. Indoor unit is hanged on the wall of a room and outdoor is placed or fixed outside the conditoned space. Split air conditioner consumes more power and electricity bills can empty your pocket. Because of long pipe runs cycle of refrigeration system becomes longer and it increases the load on compressor. Split air conditioner has less longer life and chances of leakage of gas are also high because of more joints in copper pipe at the time of installation. Split air conditioner is good for office area as it does not create sound. High installation and maintenance cost.
A split air conditioner may be ductable as shown in figure below, means through ducting network air can be distributed to different areas for air conditioning purpose.
Installation process-
1.1. Distance between outdoor and indoor unit connecting copper pipes should not be more than recommended in my opinion not more that 5 meters.
1.2. Indoor unit should be fixed on the wall at a height not more than 5feet 6inch and it should be in the exact center of the wall horizontally.
1.3. Drain pipe should not be droped to an open area without U-trap and use 1inch dia pipes for drain.
1.4. Outdoor unit should not be placed on the roof directly exposed to sun. If possible choose north wall for the hanging of outdoor unit as effect of sunshine in this direction is less as compared to other directions.
1.5. Out door unit should be hanged considering ease in maintenance for the technician.
1.6. For outdoor units there should not be any wall or obstruction near it to a distance of 3 meter in each direction.
1.1.2. Window Air conditioner :- A window air conditioner consists all components in a single unit. All the required accessories and equipments are fixed in a single body. Window air conditioner are more effecient as the gas cycle is small because no separate outdoor unit is used and no extra copper piping runs. These units dont need any copper joints as the product is completely ready to use by the manufacturer. These units are a good choice for homes. Low installation cost and maintence cost.
Installation Process :-
2.1. Installation of window air conditioner is very simple as compared to split air conditioner system. Try to fix it in the window in the north direction.
2.2. It can be placed at a height of not more than 5.5 feet.
2.3. It can only be installed in a window because condenser side is always kept outside to release the heat in atmosphere. If its kept inside a room it will produce heating and cooling in same amount and after some time it will stop working because of less air circulation arround the condenser.
2.4. Window air conditioner should be installed in a window in such a way that no gap remain between AC body and window. It should be properly air sealed so that cooling lose may not happen.
5 star rating window AC are best selection low power consumption.
1.1.3. Cassette air conditioner :- A cassette air conditoner is much similar to wall split air conditioner but indoor unit is totally different in shape and its function. A cassette air conditioner indoor unit can be hanged on ceiling using proper anchor fastners and threaded rods as shown in figure below. Indoor units can through air through a horizontal blower in two or four way directions as per requirement and return air is sucked from center grills to maintain air circulation and air conditioning effect as shown in figure below. This type of air conditioner is very quite and are very power efficient. The copper piping system is designed to work with refrigerant gas or chilled water too.
1.1.4. VRF/VRV (VARIABLE REFRIGERANT FLOW/VARIABLE REFRIGERANT VOLUME) :-
Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented by Daikin in 1982. Like ductless mini-splits, VRFs use refrigerant as the cooling and heating medium. This refrigerant is conditioned by a single outdoor condensing unit, and is circulated within the building to multiple indoor units.
VRFs are typically installed with an Air conditioner inverter which adds a DC inverter to the compressor in order to support variable motor speed and thus variable refrigerant flow rather than simply perform on/off operation. By operating at varying speeds, VRF units work only at the needed rate allowing for substantial energy savings at partial-load conditions. Heat recovery VRF technology allows individual indoor units to heat or cool as required, while the compressor load benefits from the internal heat recovery. Energy savings of up to 55% are predicted over comparable unitary equipment. This also results in greater control of the building's interior temperature by the building's occupants.
Working principle & Block diagram for various types of VRF/VRV system: There are various types of VRF system used for split air conditioning system.
1. Only Cooling type VRF system
2. Heat Pump VRF system (2 pipe system)
3. Heat Recovery VRF system (3 pipes system)
4. Hybrid VRF system
1. Only Cooling type VRF system
2. Heat Pump VRF/VRV system: This system works for cooling and heating both operation but not simultaneously. It is also known as 2 pipe system. In this system all zones or all indoor units must either be all in cooling or all in heating.
3. Heat Recovery VRF/VRV system: Heat Recovery (HR) systems have the ability to simultaneously heat certain zones while cooling others; this is usually done through a three pipe design, with the exception of Mitsubishi and Carrier who are able to do this with a 2 pipe system using a Branch Circuit (BC) controller to the individual indoor evaporator zones. In this case the heat extracted from zones requiring cooling is put to use in the zones requiring heating. This is made possible because the heating unit is functioning as a condenser, providing sub-cooled liquid back into the line that is being used for cooling. While the heat recovery system has a greater initial cost, it allows for better zoned thermal control of a building and overall greater efficiencies. In heat recovery VRF systems, some of the indoor units may be in cooling mode while others are in heating mode, reducing energy consumption.
4. The Hybrid VRF is a world first simultaneous heating and cooling 2-pipe system that uses refrigerant between the outdoor unit and the HBC (Hybrid BC controller), and water between the HBC and the indoor units. HBC is the most unique part in this system and allows heat exchange between refrigerant and water. This system is suitable for a wide variety of installations. Mitsubishi and Carrier who are able to do this with a 2 pipe system using a Branch Circuit (BC) controller to the individual indoor evaporator zones. HVRF uses advanced refrigerant technology between the outdoor unit and the HBC (Hybrid BC controller). Energy is then transferred around the building using a pair of plastic water pipes per indoor unit that can supply hot or cold water. This reduces the resources required for installation and provides a more comfortable environment.
The following major Equipment & Accessories used in VRF/VRV system:
1. VRF air cooled condensing unit (VRF outdoor unit)
Manufactures: Samsung, Mitsubishi, Trane, LG, Johnson control (YORK), Toshiba, Daikin, Bosch, Gree, Hitachi, Voltas, O-general, Blue-star etc.
Specification: Air cooled inverter scroll compressor based variable refrigerant flow/volume (VRF/V) air conditioning system suitable for Heating & Cooling (Heat pump or Heat Recovery) outdoor condensing unit with at least one inverter type compressor in each module with R410a refrigerant, suitable for 380-415 V, 3 Ph, 50 Hz supply complete with condenser coils, condenser fans, Electronic expansion valve, Solenoid valve, 4 way reversing valve, Distribution headers & capillaries, Filters, Shut-off valve, Oil coolers, Service ports, Refrigerant receiver & accumulators, inverter based microprocessor controller, including connection with outdoor unit multi-connection piping kit etc.
Capacity Range: VRF outdoor capacity ranges from 6 – 20TR (6 TR, 8 TR, 10 TR, 14 TR etc)
2. Fan coil unit (Indoor unit)
Manufacturer: Samsung, Mitsubishi, Trane, LG, Johnson control (YORK), Toshiba, Daikin, Voltas, O-general, Hitachi, Lloyd, Videocon, Blue-star etc.
Specification: Indoor unit equipped with fan section with low noise fan, multi speed motor, coil section with DX coil, Electronic expansion valve, Pre-filters, Epoxy coated outer cabinet, drain pan, corded remote controller, Y-joint header & Flaring set etc.
Capacity range: Decorative wall mounted FCU = 0.8 TR, 1.0 TR, 1.5 TR Decorative ceiling suspended FCU = up to 4.0 TR Ducted ceiling suspended concealed type FCU = 2.0 TR to 8.0 TR Cassette type FCU = up to 4.0 TR Floor mounted Decorative type FCU = 4.0 TR to 10.0 TR
3. Hybrid Branch Controller (HBC): The HBC (Hybrid BC controller) allows simultaneous cooling and heating of Hybrid systems by connecting several indoor units to one outdoor unit using only two pipes. It has a built in heat exchange between refrigerant and water. Plastic water pipe is then used between the HBC and the indoor units.
4. Separation Tube Assembly (STA): VRF piping improves refrigerant cycle efficiency and reduces piping cost by connecting multiple indoor units to a common liquid and suction line through the use of Separation Tube Assemblies (STA) and/or Headers which diverts the common flow of refrigerant to an individual evaporator. The flow of refrigerant is further metered by an EEV or Electronic Expansion Valve.
5. 4 way reversing valve: A heat pump reversing valve is an electro-mechanical 4-way valve that reverses the refrigerant (Freon) flow direction, using an electrical magnet. Frist let’s see what a heat pump reversing valve looks like. In the figure below, you will notice the valve has 4 tubes or connections; A, B, C, D. This valve is also referred to as a 4-way valve.
Cooling Mode (Energised mode): The heat pump reversing valve has 4 large tubes (A, B, C, D ) that’s why they call it a 4 way valve and it also has:- capillary tube (1), capillary tube (2), capillary tube (3), slider (4), block (5) ,electrical coil (6), electrical magnet (7), and spring (8). Notice that the compressor’s discharge port (high pressure) is always connected to tube A in the reversing valve and the return port (low pressure) in the compressor is always connected to tube B.
Therefore tube A always has higher pressure refrigerant, and tube B always has lower pressure refrigerant. Notice also that capillary (2) is always connected to tube A, thus capillary (2) also has a high pressure. When we energize the electrical coil (6) it energizes the magnet (7) that pulls the block (5) which will blocks the capillary tube (3) and compresses the spring (8). Got it? Great, so notice that the capillary tube (3) is now blocked, and the high pressure refrigerant will flow from capillary (2) to capillary (1) straight to the left side of the heat pump reversing valve’s body that will push the slider to right hand side from the valve’s body which will allow the high pressure refrigerant to go from the tube A to tube D to the outdoor coil, through the metering device to drop its pressure, then to the indoor coil to cool the inside of the house (cooling mode) then back to tube C. If you had notice the slider has a top groove which allows the low pressure refrigerant to flow from tube C to tube B then back to the return port in the compressor to repeat the cycle again.
Heating Mode (De-energised mode):
Please notice that the coil (6) lost its power, or de-energized, which makes the electrical magnet (7) lose its magnetic power. When this occurs, the spring (8) will decompress and push the block (5) to the left, and block the capillary tube (1). I am thinking you are becoming an expert by now!
The capillary tube (1) is now blocked and the high pressure refrigerant will flow from capillary (2) to capillary (3) straight to the right side from the reversing valve’s body. This in turn will push the slider to the left hand side of the valve’s body which will allow the high pressure refrigerant to go from the tube A to tube C. This allows refrigerant to flow to the indoor coil to heat the inside of the house (heating mode), then through the metering device to drop its pressure then to the outdoor coil then back to tube D. Again the slider has a top grove this will allow the low pressure refrigerant to flow from tube D to tube B then back to the return port in the compressor to repeat the cycle again. That’s it that’s how the heat pump reversing valve works in real-life.
6. Electronic Expansion Valve (EEV): Electronic expansion valves replace mechanical expansion devices, improving control of refrigerant flow and consequently increasing unit efficiency by up to several percent. Moreover, these also have statistical advantages again of several percent as the electronic system guarantees optimum calibration at all times, unlike mechanical devices that needs to be adjusted manually and periodically.
7. Non Return Valve (NRV) for Refrigerant flow: NRV can be used in liquid, suction and hot gas lines in refrigeration and air conditioning plants with fluorinated refrigerants. NRV can be supplied with flare and solder connections to make one directional refrigerant flow in the system.
8. Refrigerant Piping: Copper tubing is most often used as refrigerant line in HVAC systems. There are two basic types of copper tubing, soft copper tube (Type-L) and hard copper pipe (Type – K). Copper tubing is joined using flare connection, compression connection, or Brazing. Copper offers a high level of corrosion resistance, but is becoming very costly. Soft (Type - L) copper tubing with medium thick wall can be bent easily to travel around obstacles in the path of the tubing. This type of copper tubing suitable for flare connections. Soft copper is the most popular choice for refrigerant lines in split-system air conditioners and heat pumps for small run of refrigerant piping (Horizontal up to 3 mtr). Flare connection is mostly used for soft copper tube connection.
Hard copper tubing (Type – K) is mostly used for long run of horizontal/vertical refrigerant piping. Hard copper tube is of thick walled and hence cannot be bend and must use various copper fitting such as elbow, reducer and sockets to make a turn, reduce & connect other piece of pipe respectively. Soldering are mostly used for hard pipe connection.
Types of Copper piping connections:
1. Brazing connection: This joint is heated with a torch using the mixture of oxygen & acetylene gas, and copper alloy filler is melted into the connection. When the brazed joint cools, it forms a very strong bond which can last for decades.
2. Flare connection: Flare connections require that the end of a tubing section be spread outward in a bell shape using a flare tool. A flare nut then compresses this bell-shaped end onto a male fitting. Flare connections are a labour-intensive method of making connections, but are quite reliable over the course of many years.
3. Compression Fitting: Compression fittings use a soft metal or thermoplastic ring which is squeezed onto the pipe and into the fitting by a compression nut. The soft metal conforms to the surface of the tubing and the fitting, and creates a seal.
9. Refrigerant pipe insulation:
1. Nitrile Rubber Insulation: Nitrile-rubber foam insulation that is closed cell, flexible and has a built-in vapour barrier. Density with 60kg/m3, working temperature range -200 to 115 ℃, thermal
conductivity 0.037 W/m⁰K and resistance to oil & grease. Insulation tubes are available in size ¼” – 4” of length 2 mtr with insulation thickness 9mm, 13mm, 19mm, 25mm. This is widely used in HVAC refrigerant piping insulation.
2. Polyurethane foam (PUF): PUF pipe insulation with density 36 kg/m3 and thickness ranges 25 -100 mm with facing of aluminium foil or kraft paper is widely used for Pipe and duct insulation.
3. Polyethylene Foam (PEF): Polyethylene Foam is a strong and resilient closed cell foam available in sheets, tubes & cylinders. It is widely used in HVAC piping for light weight, super strength & tear resistance
1.1.5. Packaged air conditioner:- A packaged air conditioner is similar to a window AC, all the components are installed in a singly body but packaged air conditioner is used for large areas like halls, offices, shoping outlets, marriage palaces or a big house. A package air conditioner needs ducting system to deliver conditioned air to space and retrurn air from the space returns to the units by duct or by path through which supply air duct is passed. A packaged air conditioner may contain single circuit, double circuit or three circuits piping networks and for each circuit an individual compressor is installed.
2. Chiller system:-
A chiller is widely use in high rise buildings like hotels, shoping malls, Hospitals etc for air conditioning. Chillers are used for high cooling capacities requirements in industries as well. A chiller may be water cooled or air cooled means the condensation of refrigerant is done either by air or water through cooling towers. An individual plant room is considered for placement of these chillers in building. The water is circulated through FCUs, AHUs or any other indoor unit through piping network using Pumps. Water works as a medium for air conditioning instead of refrigerant. The refrigerant only circulates in copper piping network in chiller and water circulates through all over the building.
