InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website. This article describes the procedures for charging an air conditioner, heat pump, refrigerator, freezer, or similar equipment - how does an HVAC service tech put the proper amount of refrigerant into the system?
We describe use of a traditional charging cylinder, vaporizing connectors for low-side charging, and modern refrigerant recovery, charging, and vacuum equipment. As we've explained, charging an empty system will require evacuating it first. For a typical household equipment this takes about 15 minutes but for a larger commercial refrigeration system this process can take an hour. On commercial systems being installed or having major service it would be preferable to leave the evacuator pump running for 12 hours - the longer you evacuate the system the cleaner it will be.
That's because as the system warms up moisture in the system will vaporize further and thus be removed. Low side charging is also referred to as vapor charging - that is we allow ONLY refrigerant vapor or gas to enter the system. This is an easy but time consuming method of system charging. The canister supplying refrigerant is connected to the gauge service port and opened, and the HVAC equipment or appliance is run which pumps refrigerant gas from the supply source in parallel with pumping from the outlet of the evaporator coil.
A step by step example of low-side charging of refrigerant on an older R22 system can be seen. When charging an air conditioner, heat pump, or refrigeration appliance from the high side, the system being serviced is turned OFF. The refrigerant gas canister is placed upside down so that only pure liquid refrigerant leaves the canister.
Note that once you start the system running you will not be able to charge on the high side because the head pressure out of the compressor will be higher than the evaporation pressure in the canister - it would push refrigerant back into the canister.
With critically-charged HVAC or appliance refrigeration systems, such as a household refrigerator or air conditioner, you must measure the refrigerant entering the system. Typically the technician uses a scale that registers in ounces to measure a weighed charge, though we also used other devices such as a charging cylinder that actually shows the volume of liquid refrigerant in the cylinder on a temperature-compensating scale.
In this case the charging board Dial-a-Charge charging cylinder produced by Robinaire, Montpelier OH is loaded with the proper refrigerant charge from the gas cylinder, and the outlet from the charging board is then connected into the high side perhaps through the gauge service port.
The refrigerant vaporizing connector such as Imperial's Kwik-Charge, assures that liquid refrigerant passing through the device will convert to gas as it exits the device. This will let you add a measured refrigerant charge to the low side of the system while still making an accurate measurement of the refrigerant measured in ounces.
Liquid refrigerant charging is always faster than low side vapor charging. On the low side you have to charge, then wait for the system pressures to balance, then reexamine the frost line etc.
As an alternative to making refrigerant measurements by weight or temperature-corrected volume using a scale or charging cylinder, some HVAC service technicians may adjust the refrigerant charge by watching the low side pressure and the exact location of the frost line at the evaporator coil blower fan not running.
On small refrigeration systems such as a home refrigerator or window air conditioner the refrigerant charge needs to be accurately measured or the system will not work properly.
But on larger HVACR systems and on commercial units that use a liquid refrigerant receiver a sort of buffer that stores extra liquid refrigerantyou might find a sight glass on the refrigerant piping downstream from the condensing coil.
Some techs add refrigerant while watching that sight glass, adding refrigerant until the gas bubbles just stop. If you see bubbles there either the system is badly contaminated or more likely the refrigerant charge is short.
We warned just above - don't overcharge the system - you can damage the equipment. Technical Note : if you see bubbles in the sight glass, or if you hear gurgling in the refrigerant lines indeed those can be indicators that the refrigerant charge in the system is low. Note that a reading of "zero" on these pressure gauges is not really zero, it's 14 psi or 1 atmosphere.Refrigerant charging might be the least understood practice in the air conditioning industry next to setting airflow.
Although there are several methods, typically there is only one correct method for the type of unit you are working on.
Information contained here is for formally trained EPA Section certified technicians. When a system is equipped with a fixed metering device or capillary tubes, the total superheat varies with the outdoor air temperature and the heat load on the evaporator air temperature and humidity. Overcharging and undercharging both have a considerable impact on efficiency and humidity removal so the correct charge is critical to proper operation and creature comfort.
The total superheat method is the most accurate method of charging fixed orifice or capillary tube systems. These systems are critically charged and require correct airflow and accurate test instruments to properly and accurately charge the system.
Because these systems do not "control superheat" it is critical that the airflow be as close to possible to correct prior to charging as the system will be charged to the airflow.
The total heat in the air will be the driving factor for the evaporator performance so low or high airflow will have a direct impact on the charge and the system performance. Click image to enlarge! Charging by weight is one of the most accurate and fastest methods of charging a system that has a known refrigerant charge. Typically this method requires an already evacuated system that is ready for charge, or removal of the existing charge so the proper charge can be weighed in.
Because exact length of the line set is often hard to determine within a few inches, we recommend the initial charge be determined by either the Total Superheat or the Subcooling method. If the exact charge is known, use a high accuracy high resolution digital scale to weigh in the entire charge.
If provided by the manufacturer and the system is new and or completely clean, the system can be accurately charged by measuring the suction pressure, measuring outdoor air temperature and then adding charge until the liquid pressure is at the chart requirement. After the charge is complete, verify proper temperature split to assure acceptable system airflow. This is the common method used by Rheem and Rudd and others for initial charging. Because this method is pressure and temperature driven, cleanliness of the coils is critical to your success.
Typically the chart supplied with the equipment is specifically for that piece of equipment and cannot be used with other models. In order to verify charge by the approach method, the evaporator airflow must be properly set, and the evaporator coil and condenser coil completely clean. Find the required approach in the manufacturers installation instructions, which will be specific to the condenser you are servicing. Measure the outdoor air temperature entering the condenser from top to bottom of the coil outside of line of site of the sun and obtain an average condenser entering air temperature.
Measure the liquid line temperature with an accurate clamp probe thermometer. Determine the temperature difference between the liquid line temperature and the outdoor air temperature.
This temperature difference is the approach temperature. Adding refrigerant will decrease the approach and removing refrigerant will increase approach. Allow minutes of operation for the approach to stabilize after refrigerant is added or removed. After the airflow and the refrigerant charge have been set, verify that the system is operating at its rated capacity by measuring the actual airflow and measuring the change in enthalpy across the evaporator coil. Enthalpy is determined by converting the return and supply wet-bulb measurements using the enthalpy chart provided here or at the beginning of this document.
Use the Commissioning Worksheet to determine the capacity of the system. Procedures for Recharging Air Conditioning Systems with Refrigerant Refrigerant charging might be the least understood practice in the air conditioning industry next to setting airflow. Start with the basics for all systems: Makes sure the system been properly installed and evacuated.
Refrigerants are divided into groups according to their chemical composition. Following the discovery that some of these chemical compounds may be harmful to the environment, they are being replaced with more environmentally friendly alternatives see Figure 5.
The process is not easy, and although there are alternatives to old refrigerants, the new ones are usually not flawless. In the following section, different groups of refrigerants are discussed, some examples are given and their fields of application are described.
Chlorofluorocarbons are refrigerants that contain chlorine. They have been banned since the beginning of the 90's because of their negative environmental impacts. The conversion of equipment and systems using CFCs has not yet been completed. The slow phase-out of CFCs shows it is a costly process. However, and more importantly, it also shows the problems and indecisiveness surrounding the availability of HCFCs, which were officially indicated as temporary until substitutes for CFCs.
The hasty actions of the European Union that culminated in the ban of HCFCs, immediately for refrigeration and soon at the latest for air conditioning, has upset the industry's programs and plans. Examples of hydrochlorofluorocarbons include R22, R and R see Figure 5. However, their impact on global warming is very large compared with traditional refrigerants. Fluorocarbons Figure 5. However, they are extremely stable, and they have a high GWP cf.
R is an example of a fluorocarbon, and FCs are also present in the mixtures R and R Hydrocarbons are a very limited solution to the environmental problems associated with refrigerants.Refrigerant Charging for R-410a Condensing Units
The use of HCs as refrigerants is confined to Europe, because many other countries elsewhere have banned the use of flammable gas in the presence of the public. However, the standard IEC This standard has opened the way for some European refrigerator manufacturers to produce household refrigerators with flammable isobutene, Ra.
These have been accepted enthusiastically by environmentalists, and have achieved great success in the market. Ammonia, R, is an attractive refrigerant alternative. It has been used in refrigeration systems since and in vapor compression since Let us assume that you have located and repaired the leak which caused the undercharged conditions.
You now wish to top up the refrigerant charge and have hooked up a jug of the appropriate refrigerant. Click the Charge button to open the low side hand wheel on the gauge set and start charging. Notice all the things that change as you are charging. The yellow colour is used to indicate the route that the refrigerant takes when you allow flow from the jug. Gas will flow because the pressure in the jug is greater than the pressure in the low side of the system. High pressure flows to low pressure just as high temperature flows to low temperature.
When you open the low side hand wheel you can see the suction pressure increasing on the low side gauge. You can also notice a slight increase in high side pressure and you now know why.
This vapour is being introduced into the suction of the compressor and there is nothing wrong with that. This method works well with small to medium sized systems but if you need to charge a large system you might be there for very long time indeed.
If you vapour charge for several minutes you will notice a decrease in available pressure from the jug. You will also notice that the jug is getting colder and colder. That makes sense because we know low pressure goes hand in hand with low temperature. We can't get away from the laws of physics.
When you draw off some vapour from the jug the Pressure Temperature Relationship forces some liquid to flash into a gas to make up for the vapour you just removed and keep the Pressure Temperature Relationship in balance. But by changing state that liquid has created the refrigeration process and removed heat from the surrounding area which in this case is the rest of the liquid refrigerant in the jug. If you continue vapour charging long enough the drum may get so cold that you lose all of your pressure differential and can no longer continue.
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One solution is to warm up the contents of the jug. Don't even think of playing a torch on the jug. You must never do that. A safe method to warm up a jug is to place it in a pail of warm water or if you prefer run warm water over the jug in a sink.After you enable Flash, refresh this page and the presentation should play.
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Toggle navigation. Help Preferences Sign up Log in. To view this presentation, you'll need to allow Flash. Click to allow Flash After you enable Flash, refresh this page and the presentation should play. View by Category Toggle navigation. Products Sold on our sister site CrystalGraphics. Title: Refrigeration Basics Description: Refrigeration Basics By: Eric Nelson Basics Refrigeration is the removal of heat from a material or space, so that it s temperature is lower than that of it s Tags: basics refrigeration.
Latest Highest Rated. Title: Refrigeration Basics 1 Refrigeration Basics By Eric Nelson 2 Basics Refrigeration is the removal of heat from a material or space, so that its temperature is lower than that of its surroundings. When refrigerant absorbs the unwanted heat, this raises the refrigerants temperature Saturation Temperature so that it changes from a liquid to a gas it evaporates.
The system then uses condensation to release the heat and change the refrigerant back into a liquid. This is called Latent Heat. This cycle is based on the physical principle, that a liquid extracts heat from the surrounding area as it expands boils into a gas. To accomplish this, the refrigerant is pumped through a closed looped pipe system. The closed looped pipe system stops the refrigerant from becoming contaminated and controls its stream. The refrigerant will be both a vapor and a liquid in the loop.Toggle navigation.
Help Preferences Sign up Log in. Featured Presentations. HFC Refrigerants Market: high demand in Industries for refrigerants across the globe through - Refrigerants are generally in fluid form and are used in a heat pump or refrigeration process. Refrigerants are generally in fluid form and are used in a heat pump or refrigeration process.
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Join Jens as he shares knowledge gained from over 40 years of experience in the cooling industry. CoolTalk : Charging new refrigerant. Put your skills to the test with Cool Game 3. First players to get a high score win a prize! Plays best on desktop. Converting to the correct refrigerant requires the right refrigerant tools.
We created these digital solutions to help you select the right refrigerant for your situation, find a compatible component, and ensure that the refrigerant is installed correctly in the cooling system.
Danfoss offers a variety of educational solutions to help you understand the refrigerant changes and make the best decisions about how to adapt to them. Watch videos, take online courses, attend webinars - we have something for everyone. Get the keys to understanding the refrigerant regulations and trends in air conditioning and refrigeration. Our portfolio for low-GWP refrigerants is continuously expanding. Take a deep dive in this brochure and contact Danfoss for more information.
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