Ever wondered how you get cool breeze from air conditioner. What is the mechanism actually involved in producing cold air in burning hot summers? Here is the simple diagrammatic explanation of working principle of an air conditioner. No matter what type of air conditioner you are using, windowed, split wall mounted (PTAC), cabinet floor standing or roof top type, basic principle is same for all of them. Even inverter air conditioner that has got modifications in primitive design still follows the same principle and laws of thermodynamics.
Basic Mechanism And Principle
Explanation: Every air conditioner (also pronounced as AC, A/C or Air Cooler in certain regions of the world) has got a compressor inside it. It works to compress and pump the refrigerant gas. Compression of refrigerant produces heat. To dissipate this heat, compressed refrigerant is pumped to the condenser coils where a fan blows the heat out to outer atmosphere. During this process, refrigerant takes the liquid form. This liquid refrigerant is pumped towards expansion valve. Expansion valve has a temperature sensor connected to it which works in correlation with thermostat settings. Expansion valve releases the appropriate amount of refrigerant to evaporator (cooling coils) where liquefied refrigerant takes gaseous form. Conversion from liquid to gaseous state due to expansion causes cooling because energy is absorbed from the surrounding. Air when passes through fins (attached to coils) gets cooled and blown to the room. The gaseous refrigerant in cooling coils then enters the compressor and gets compressed once again. The cycle continues unless the compressor is shut down.
In a nutshell, air conditioner draws heat from the indoor and releases it to the outdoor. Indoor acts as a source and outdoor as a sink for heat.
In vehicle air conditioners, a Receiver-Drier is installed between condenser and expansion valve. It serves to collect excessive refrigerant when not required for cooling operation. It also has got a desiccant which absorbs any moisture present in the refrigerant.
Inverter air conditioners: These air conditioners use an inverter to control the speed of compressor. Electricity is first rectified to DC (direct current) and then inverted back to required frequency AC (alternating current) using pulse width modulation. Thus compressor speed can increase and decrease according to the room temperature. Such air conditioners are extremely energy efficient and consume approximately 30-60 % less electricity than old fashioned air conditioners. Inverter air conditioners are expensive due to the additional machinery inside them but cost is slowly recovered in electricity bills. Their other advantages include quiet operation, faster cooling, no indoor temperature fluctuations and no voltage peaks caused by compressor.
Air conditioner as a heater: When air conditioner is used as a heater, the process which is shown and explained above just simply gets reversed. As a result of reverse mechanism, hot air is propelled towards indoor and cool air towards outdoor.
Thanks very much for the information. but I was just wondering for ACs that are configured to perform both heating and cooling, How is their expansion valve configured to work both ways???
Expansion valve just releases the pressure of gas. The valves for such air conditioners that perform heating task are designed to release expanded gas to condenser coils (reverse mode) thus cooled air is thrown outdoors. Condenser also has got its own thermal bulb (sensor) to control the valve.
Hi Talal ! Does condenser has thermal bulb to control expansion valve? How it works? I’m asking bc It’s brand new information for me. what I know is that if you want to use ac for heating you have to reverse evaporator to be in the outdoor and condensor to be in indoor. But it’s impossible to change this components every time when you need cooling and the other time heating for your home. So just ac would be installed evaporator inside but for the case of heating there would be heater or other form of heating the air at the outlet of the fan. If I miss something pls correct me. Thank you.
What is thermal bulb?
It is attached to evaporator and thermal expansion valve (TEV) and cause valve to open or close. (TEV is also known as TXV)
I like this article, but for the proper operation of the expansion valve, the temp sensor or “thermal bulb” must be located on the tail coil of the evaporator not on the entry coil. If located on the entry coil, it will not correctly modulate in response to the temperature change of the refrigerant as it changes from a liquid to a vapor ultimately resulting in a “starved” evaporator and insufficient cooling of the application.
OK. So, we compress the gas, it warms up during that process, so we cool it down in the condenser which will cause it to return to it’s liquid form. Then it passes through the expansion valve. Here is my question. if it is still in a liquid form after the expansion valve, what is causing the refrigerant to become cold. Or is it already in gas form when it leaves the expansion valve?
Expansion valve expands the liquidated gas. It turns to less compressed refrigerant.
What’s centralised air conditioning?
Cold or hot air is supplied through ducts in walls or roofs to every room in a building.
Is there a specific position in a room where we should install a split a/c? Or any position will cool the room? Kindly suggest.
Install it anywhere. But if it is a bedroom and you want cool air directly hitting the bed, install it near the bed.
I found some water drops are coming out from the exhaust box It was second hand ac is there any solution
It’s normal. Do not block the drain.
Can you please explain how compressor and AC Motor of Fan are controlled by Electronics.. What is the functionality of the board present in outdoor unit?
Inverter air conditioners have complex electronics circuitry inside them as inverter controls compressor speed. Traditional air conditioners also have basic electronics to monitor what’s going on and trigger specific functions. Google the circuit diagrams for such electronics. You may find more information.
devendra Kumar Sahu
Sir as we know that the evaporator absorbs the heat of body and use that heat as to convert the liquid state of refrigerant into superheated steam….. But if the temperature of body is low then the heat produce will also low so how refrigerant convert into steam…..??
Well first of all liquid refrigerant does not convert into steam after expansion. It changes to gaseous state because refrigerant used in system is already a gas. In evaporator, gas is already cool due to expansion from liquid state. But this refrigerant is actually extremely hot when it leaves compressor after compression and enters condenser. Condenser is just used to dissipate excessive heat out of the refrigerant.
Very good information. Thank you.
does the ac allow cool air to enter inside the room? and throw out the heat outside the room?
It does not directly throw hot air out. The hot air that you feel coming out of the outdoor unit is the heat that was generated when gas was compressed. Once gas expands, it causes cooling. This cool refrigerant when passes through coils of indoor unit, produces cold air. So generally speaking, we may say that indoor heat was thrown away and replaced with cooler environment.
All your replies are quite informative. I would like to know about the amount of electrical power needed for the compressor. Is it possible to power the compressor directly from Solar PV. Pls reply sir.
Yes. It can be powered. Depending upon the power requirements, you will need solar panels that can supply enough power to run it directly. Otherwise, you can charge batteries connected with Solar power system and use their backup to run compressor. I am sure by compressor you mean compressor of air conditioning unit?
Well explained and elaborate. Really helpful also
please does room air condition have expansion valve and receiver dryer
2.can I repair my spoil compressor if yes what method will I use
3.my refrigerator is working but only the freezer side and I have done all a mechanic can do please any tips help me out…
For an air conditioning system to operate with economy, the refrigerant must be used repeatedly.
What is the star which indicated on aircon. what it mean?
What are the factors that the efficiency of ac system depends on? Will the efficiency reach 100%?
sir i need your help
i want to use cooler as a heating and cooling both purpose so suggest me
Can you tell me the material used for making compressor,Evaporator?
I’m writing a report and i’m wondering if its okay if i reference your page
dear sir, im not familiar with ac system, as i understood compressor helps to maintain the circulation of gas like a pump and expansion valve causes the change of liquid form to gas hence the cooling of pipes. please correct if im wrong and pls explain how expansion valve changing liquid to gas
AC Compressor is a gas compressor plus gas pump.
Expansion valve releases appropriate amount of liquified gas into evporator coils which expands and cause cooling.
Hi, In my case, it is fitted on the upper open, on the parapet wall facing east. That could not be changed. Is there any thing that i could do . I am asking this because, if i cover the whole thing, then there is restricted air circulation and it would even burst.I do not know for sure. Is there any remedial measures of this type of problem, sir
If you can not shade it then leave it as it is. Just do not run it when it is raining or you will damage its fan.
Hi, This is informative and educative. Would you include the maintenance of compressor, which is always under the mercy of outdoor temperature, It is in open condition and exposed to outer atmospheric pressure. Do we have to cover it up or give a shade top to it. Is there any maintenance tips
Always install it in shade where direct sunlight and rain do not fall on it. While servicing air conditioner use dust blower to clean fins of outdoor unit. That will increase efficiency of AC.
Hello sir, i have read through people questions and and their anwser respectively, my question here, is that: what is the causes of an ice (freezr) in both suction and liquid side of a tubes true evapourator and it‘s solution?
Probably low refrigerant.
I don’t think so the cause is ‘probably low refrigerant’. low refrigerant means there is no enough amount of gas which takes out the heat in the air and make it condense. I think the cause may be not enough air is supplied to evaporator so this insufficient air gets condensed easily across evaporator. The cause may be fan problem, filter clogged.
there was a leak in the joints, repaired and put one unit of Freon in it.The next day same thing same tech returned said their was probably some ice residue in the lines causing the problem, checked the lines, filled completely with Freon. Said it that didn’t work, might be the fan (?)Paid for twice, still freezing up .air conditioning company will not return our calls.
Dawood ibrahim Ali
Sir, which type of AC. Has greater efficiency
Thank you very much for your explanation.
I have a question,after compressing the gas it becomes hot and the fan makes it a bit cooler but how it condensate it?(we know that the fan is not adequate to condensation)
Compressor does that.
I see you explained many question clearly and correctly, but this one in my perspective isn’t right. Compressor doesn’t condense the riferigerant in a condenser. The condensation level across condenser is different,. Inlet of condenser is a compressed gas but when it goes to the outlet it slowlely gets condensed and in a normal working ac almost become liquid refrigerant at the outlet of condenser except some moisturizer refrigerant. normally the design of condenser ( length, pipe thickness, material,) , fan capacity , compressor outlet pressure are the whole factors to make the refrigerant condensed on the outlet of condenser.
water comes out from room by AC . why and how it comes ..the principle? how this water form …??
It is the water of condensation. Just like water vapors form on glass of cold water, water vapors build on cooling coils that are drained.
I installed a window mounted ac inside my laundry room… its great cuz i am able to dry my laundry while the aircon is running ( the laundry area is about 4x6x8 ft.). The laundry is vented to allow hot air. My question is : Since the laundry area is enclised with large vents only, does it affect the the aircon cooling temperature inside since it is enclosed as such , the temperature builds up inside the laundry area ?… compared to an open air vented exhause mounted…. i live is asia and summer days gets up to 100 degrees farenheit….
Open vents do affect cooling.
Palash ch santra
Explain the working principals of a roof mounted package unit with proper diagram and also explain temperature & pressure details of reffrigerant gas R22 at every pipe line position and also clarify the needness of different dia copper pipe used
Palash ch santra
1:-) what is the function of accumulator?
2:-) explain the characteristic of F22 gas and is it harmful?
Accumulator holds refrigerant so that it could convert fully to gaseous state before entering compressor. Also carries desiccant to absorb any moisture present in refrigerant.
some ac’s act as dehumidifiers . how it is possible?
the case is same just like previous question of ankur,another problem is, in that case will we have to light incense stick(agarbatti) in room.(there is less chance to change the function of a.c).kindly give me advice of previous and this problem at this site and also send the require the information on my email id.
Fragrance of any sort does not help. The little space beneath doors is also enough for fresh air. Some air conditioners also have got fresh air function. You may select such air conditioners. Otherwise, there is nothing to worry about. Just do not burn anything inside closed room as burning stuff consumes much more oxygen in few minutes than a person will in several hours.
I often listen to the people filing up gas for A.C, After how long it needs to be fill up., Is it carben dioxide which you had explained or any other.
No need to change gas. It is done only if compressor is running low on gas.
sir I want to know the exact details of 4 stroke and 2 stroke engines
in a room there r 4 persons and room r closely packed and there r no windows except one gate is there .but main problem is the gate where it is situated is in central position of flat. so there is very less chance of fresh air to come inside the room. will it be a long term health problem.in that case what is solution of this problem.kindly give the advice,soon
Centrally air conditioned buildings have fresh air system as well. Open the door or windows for few minutes. That will let enough free air inside. With only four person, a large room won’t cause any suffocation.
Deo Narayan Singh
Quite informative and very well explained. The conversation section is even more educative.
yes I like this information but air cooler is global warming of world.
My question is why we flush copper piping with Nitrogen Gas before injecting Refrigerant. Can’t we use other gases to flush except Nitrogen.
It’s to prevent copper from rusting.
GENERALY WHAT TYPE OF COMPRESSURE USE IN ROOM AC
Compressor mechanism is almost the same for all types of air conditioners. Different manufacturer might use different material for manufacturing them. Size and shape also varies.
Why silica gel is used in air condition?
As per the last comment, we need to use AC with windows open, will it not consume more energy? If yes how to save electricity? How much window should be open for 2.5 sq mt room, if u use AC only at night for 7-8 hrs and it is open in other times, to avoid low oxygen? Kindly give advice.
You do not need to open any windows. The gaps found below doors can supply some fresh air. Opening a window is required only when you burn something inside room. Fire quickly consumes all oxygen present inside. Besides, see if your air conditioning support fresh air. Choose fresh air option so, outside air is supplied mixed with circulating air of room. Other than that, no need to worry.
in a room same air in different temp conditions is spread; if 3 persons spend 5 days in a closed room the percentage of oxygen thus reduces and carbon dioxide increases; there is no mixing of fresh air in split ac.is it not a great health hazard? and what is percetage of oxygen after 5 days in 12’x12′ room.pleas e explain
Percentage of oxygen decreases because people inhale it and release carbondioxide. The room should not be made air tight. There should be windows for fresh air. Those buildings that are centerally air conditioned are also supplied fresh air along with cool or hot air through air ducts.
Sir , i am going to attend an interview in an AC company for engineer posting.i dont have experience in relevant field. I completed my BE MECHANICAL and had experience in qc for 15 months
now what i want to know while attending interview in AC company. please help
what are the different types of gases used in A.C.? ..EXCEPT CARBON DI OXIDE
Now, tetrafluoroethane or carbon dioxide is mostly used. But Nitrogen is also used as refrigerant. Previously, CFCs were also used but their use has been banned worldwide.
What is the work of a receiver in an a.c system and also what is the effect of an a.c system working without dryer.
Dryer dries the refrigerant from any moisture. Without it, the vehicle A/C won’t work efficiently.
i found during my inspection at some units frost in the coils at the outdoor unit connection and in indoor unit.is this is because of excess cooling of refrigerant or improper control of expansion valve?
Low refrigerant can cause this.
thanks for the information, and i have a small doubt which gas is used as a refrigerant? Is it the carbon dioxide alone or also the oxygen and nitrogen which is also present in the room temperature.
Carbon dioxide is used as a refrigerant now.
Can a car ac be used as room ac to run with battery and inverter and if so what is the capacity of the dc motor ?
No, you can not. Car A/C is designed to cool a small cabin of car. Secondly, AC compressor of car is run with a belt attached to engine. There is no DC motor to run it.
high pressure liquid from the condenser becomes low pressure liquid when passed through expansion valve but how this liquid becomes cold in evaporator?
It changes its form from liquid to gaseous which causes cooling.
gaseous property bigger the size of gaseous atom cooler it will be
Thankssss… a lot for the quick response… and for uploading this info.. :-)
i’ve gone through this… but my question is how does water comes out from the pipe connected to the AC??? i mean if after condensing all the water is again converting to gas again.. then how does the water comes out?? can u plzzz help me out!!
Water that builds up at evaporator coils is drained through drain pipe. That water is actually the moisture of room which condenses and converts to liquid form (water) and drained. Take an example of glass of ice cold water. On the outer side of that glass, you will see condensation of moisture in air. Same is the case for AC evaporator coils. That gas which you are confusing is actually present inside the closed loop of pipes and compressor. That never leaks out unless there is some leakage somewhere in which case you will have to refill the refrigerant in compressor.
My car AC has got receiver/dryer attached to condenser coils inside the engine bay.
I actually have a doubt.if the gas is compressed and condensed again,why don’t we use liquid already so that we don’t need the compression process.the condensation process produces cooling effect.then why we compress the gas to liquid instead of taking it in liquid form??????plz help me if anyone can explain.I m a student so forgive if question is silly.plz help.
Liquid can not give the required results which a gas can. So, we use gas (tetrafluoroethane, carbon dioxide or nitrogen) in air conditioners. Condensation of gas (conversion from gaseous state to liquid state) produces heat. This heat is dissipated in atmosphere with the help of condenser coils of air conditioner. Actually, it is the expansion or evaporation which produces cooling effect. Take an example of room air cooler in which water is used for cooling the air. Water converts into water vapours (gaseous form) which produces coolness. Same is true in case of trees. Trees cause evaporation of absorbed water and therefore cause decrease in atmospheric temperature. Another example is of sweating. Our body sweats (evaporation of our body water) and we feel cooling effect. The simplest way to understand the ac mechanism is we use energy (electrical+mechanical) to convert gas to liquid form inside the compressor. So, the excessive heat energy produced as a result (remember energy can converts its form) must be radiated out first before converting liquid back to gaseous state to obtain desired chillness.
we can use AC as a HEATER….
WILL U PLZ ELABORATE FOR ME…?
Not all air conditioners. Only those that has the function of reversing the flow of refrigerant. They come equipped with cooling and heating functionality.
When we use heater it heats the surrounding and the air present in the surround absorb that heats as a result the surrounding becomes hot in winter season
///Condensation of gas (conversion from gaseous state to liquid state) produces heat. ////
///Actually, it is the evaporation which produces cooling effect.///
Wrong understanding. Kindly relook. Joule–Thomson effect is the basic principle of AC, refrigerators etc. When a gas is expanded through a small valve it losses its thermal energy. When it is done repeatedly in a closed systme, the gas losses its energy repeatedly thereby the total system is cooled.
It’s all about energy! We can provide energy to gas by compressing it to liquid form, which is subsequently energy released by change of liquid form to gaseous form. Since, liquid can NOT be compressed, it can’t be used.
It is easier to flow the gas by compression throughout the capillary tube and also has greater efficiency to heat dissipation to surrounding as compared to liquid
Quite informative and very well explained.
What is working principle of air conditioner