Now again continuing with our vapor charging process, the charging cylinder must be weighed before charging by using a weighing scale.
In the picture, the manifold valve to the blue hose is closed so the blue gauge is measuring the pressure inside the running system. However, this method should not be used for recovering large amounts of refrigerant because mixed in with the high-pressure liquid will be the system’s oil.
This way liquid refrigerant gets admitted safely, but since the throttle valve reduces the pressure across the expansion valve, the system doesn’t run normally. Low refrigerant charge is harmful to the environment, if we have not checked or repaired the leak then it may release the refrigerant again into the atmosphere. Connect all the hose 1, 2 and 3 with the HVAC kit. On a running system, the liquid pressure does not have a consistent range like the vapor pressure does.
If you want to learn the full Total Superheat Charging Method, check out this article!
This will keep the vapor compressor safer from having liquid refrigerant enter it. For instance, it may be anywhere from 68 to 80°F inside the building but outside, it may be anywhere from 65 to 110°F. They make it seem like it's worse than it really is... -"There always seems to be enough money to do it right the second time". If a new R-410A refrigerant bottle had a surrounding air temperature of 70°F, the pressure inside the bottle would be 201 PSIG. This acidic solution dissolves copper tubings and extracts copper from copper-based alloys like brass or bronze present in different parts of an air conditioning system. The picture below shows a system running on a 85°F day that had 6 ounces of R-410A added.
This is because the outdoor temperature swing is much larger than the indoor temp swing. You can learn more about this setup in our book, The liquid line on a running system will have a higher pressure than the pressure inside the recovery bottle as long as the recovery bottle does not have air, nitrogen, or a mix of multiple refrigerants inside. So it’s better to find out the cause as many refrigerants are falling into the category of ozone layer depletion and global warming potential. However, this method should not be used for recovering large amounts of refrigerant because mixed in with the high-pressure liquid will be the system’s oil.
The indoor wet bulb temp shows the heat load on the inside of the building because it takes into consideration both temperature and humidity. In the example of an R-410A packaged unit with a surrounding air temperature of 75°F, the pressure on both the high and low-pressure side of the system will be 217 PSIG. add more gas until the compressor shell starts to sweat. In this article, we will discuss an HVAC unit’s refrigerant pressure on both the high side and the low-pressure side while the system runs. on a system that small pull deep vacuum and weigh in charge on the high side. In the above image, we can see there are two devices fitted one is an analog pressure gauge showing the final negative reading and another one is a digital vacuum gauge showing 500 microns as final reading, connected to the same line to ensure the system is 100% evacuated. Post photos, respond to polls and access other special features. Because of this, the refrigerant from the new bottle will exit the bottle and enter the system as long as the system is running and only if the service valve on the manifold connecting the two is opened. It is crucial to check the recovery bottle pressure before use! you can put it back in fine. I have read that 410a is suggested to pull 500 microns. Liquid refrigerants are incompressible and can cause severe damage to any compressor. Refrigerant is added into the liquid line for two reasons. These gases take up space in the condenser and limit the amount of liquid refrigerant leading to reduced cooling efficiency. HFC refrigerant contains chlorine which reacts with ozone (O3) to convert it into oxygen (O2) hence leads to depletion of ozone layer. Since the system has a vacuum, the liquid refrigerant itself enters the system and move towards the evaporator and condenser until the pressure comes down to the charging cylinder pressure. Once the refrigerant has charged, close the refrigerant valve of the refrigerant bottle, valve A and B and disconnect all the hoses and secure everything. In case of a hermetic compressor, it may cause deterioration of the insulation winding which may lead to a short circuit and compressor motor burn out. Procedure for a smaller quantity refrigerant charge in large refrigerating plants are performed by pump down method.
In a refrigeration system, receiver outlet is provided with a “king valve” used for liquid charging also known as a throttle valve and can trap the entire system refrigerant inside receiver.
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I look forward to responding to many more! The charging cylinder uses tables and scales for different refrigerants at different temperatures so that we can make a very accurate refrigerant charge. In between close the refrigerant charging valve A and open the throttle valve fully and check the temperature and pressure readings. If the refrigerant is added into the liquid line, the refrigerant will have to make its way through the metering device before it can enter the vapor line. If the system had R-22, the vapor pressure would be between 58 to 85 PSIG but these pressures will be dependent on the wet bulb temperature inside the building and the ambient temperature outside the building. Check out our free quizzes to test your knowledge here! Same way purge the high-pressure liquid side from 1 to 3 to remove any air inside the hose. 4. The ozone layer protects the life on earth by absorbing U.V rays from the sun, U.V rays are responsible for skin cancer, genetic damage and immune suppression in humans. If the outdoor temperature is 110°F, a refrigerant bottle outside would have a pressure of roughly 366 PSIG. The pressure in the bottle is much higher than the pressure on the low side of the system so if they are connected, refrigerant will exit the bottle and enter the system. This will cause the pressure of the refrigerant to rise.
In the picture, the manifold valve to the blue hose is closed so the blue gauge is measuring the pressure inside the running system. We have a 1,000 question workbook with an answer key that you can use to apply your knowledge as well.
Attach the temperature probe to measure the degree of superheat.
It is very important to check the pressure of a recovery bottle before using it to recover refrigerant from the system. In our, If you want to learn more about all the fine details on charging methods and troubleshooting, check out our book which is available on our, Check out our free quizzes to test your knowledge, If you want to learn the full Total Superheat Charging Method, check out this, If you want to learn the full Subcooling Charging Method, check out this, If you want to learn about Delta T, check out this, Follow us on Facebook for Quick Tips and Updates, About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”.
Where techs get into trouble is when they try to guess these pressures when checking the charge of a system. Likewise, an R-410A recovery bottle with a surrounding air temperature of 75°F should have an internal pressure of 217 PSIG. Gauge glass helps to give an idea not to overcharge the refrigerant while filling. Further more, R410a is a blend of two refrigerants and if you had a significant leak then it is likely that the mixture of the remaining gas is no longer R410a, therefore if you had a leak the best practise is to recharge with virgin refrigerant. Disconnect the charging hose 1 from the vacuum pump and connect it to the blue connection of the charging cylinder for a gas charge.
Craig creates educational HVACR articles and videos which are posted at, For business related inquires email us at, “Refrigerant Charging and Service Procedures for Air Conditioning”. Technicians use the total weight method to break the vacuum of a system with the correct amount of refrigerant needed based on the added line set length.
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Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA.