System Evacuation / Vacuum Training for Air Conditioning and Refrigeration

A suitable installation and also evacuation of and also air air conditioning system begins with a high quality installation and great piping practices.

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Short cuts throughout installation of copper line sets result in time lost throughout evacuation, potential refrigerant leaks, poor oil return, mechanism contamination and also excess time compelled for evacuation.

Proper evacuation ~ initial surroundings or after service where thesystem has actually been opened up to atmosphere is an essential to appropriate operation ofan air air conditioning system. Evacuation is a two step process ofdegassing and also dehydration. Degassing gets rid of non condensibles whichcause boosted head pressures and also increased operation cost.Where high temperatures room frequent, non condensibles an unified with moisture will additionally cause oilfailure, reduced capacity and also increased compressor wear and also potentialfailure. Losses associated with improper evacuation have the right to be an extremely high. Moisture is the 2nd issue. Humidity brakes under POE oil in HFCsystems, (like R410a) leading to premature failure of the oil. Since POE breaks downinto its an essential components, it deserve to clog the metering machine andcontaminate line sets. This could result in the need for finish systemreplacement. Moisture refrigerant and mineral oils form acids that willcause system failure as result of copper plating and damage come compressorwindings. A vacuum gauge is supplied to recognize the level of environment (degassing and also dehydration) in the system. Quick and deep evacuation of an air conditioner or refrigeration system simply comes down to correct methods including ideal installation and also assembly, maintaining out the moisture throughout fabrication and also of food the ideal tools hoses and gauges to measure up the level of degassing and dehydration. When moisture (liquid) beginning a system or condenses the only method it deserve to be eliminated is in a vapor. When it comes to system evacuation only little amounts of moisture are useful to remove this way. "It is not handy to remove big amounts of water with a vacuum pump together boiling water produces huge amounts of water vapor. One pound of water (about 1 pint) produces around 867ft3 that water vapor at 70ºF." (1) because of this in the words of David Boyd in ~ Appion, "Keep it clean dry and also tight".

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Tubing should be retained clean and also dry v the whole installation, moisture dirt and also other contaminates have the right to compromise mechanism operation and also significantly increase the time required for evacuation.Tubing benders have to be provided to minimization the variety of fittings and also reduce internal restrictions. Fittings require tube cutting, cleaning, deburring, assembly, brazing, nitrogen purging, and leak testing. The best thing to execute is remove fittings every together. A good set the benders will certainly pay because that themselves in quick order.Cut piping should be reamed or deburred. Internal restrictions can cause erosion of the piping, reduced suction gas velocity and also poor oil return. Also a couple of fittings that room not assembled properly can compromise the high quality of the installation.


Nitrogen must be purged with the piping during the installation and also during brazing to protect against the development of contaminates and moisture right into the piping and additionally to protect against the formation of copper oxides throughout brazing. Use a calibrated circulation meter to avoid using overabundance nitrogen. Scan the system with nitrogen during installation will substantially decrease evacuation times.

Install a filter dryer to remove trace moisture after evacuation. Tiny amounts the moisture can be trapped under compressor oil or in the instance of POE, bonded to the oil itself. A dryer equipped with a moisture indicator installed right before the metering machine will efficiently remove map moisture and aid quickly determine potential moisture problems. Installation the dryer inside near the evaporator will better protect the metering device, guarantee visually the 100% fluid is present, and also prevent the dryer native rusting prematurely.


After the lines and the various contents have to be installed, that is essential to make sure that there is circulation through the whole system by purging with a dried gas such together dry nitrogen from the liquid line come the suction next of the system. Purging will not only lug out little drops that water (if present) yet it will also pick up several of the mechanism moisture.

Pressure Test through a dry Gas

A standing push test is used to inspect for leaks by using a dry gas again like dry nitrogen. We never ever hope to discover leaks if in a vacuum. (Although the does happen.) as soon as air leaks in, moisture comes along for the ride which can take hours to eliminate if the lot is excessive. A temperature compensated pressure test favor that easily accessible in the Testo collection of digital manifolds will certainly make the procedure fast and also efficient. Yet if you are using a digital manifold choose the Fieldpiece SMAN, leaks will also be apparent simply because of the high resolution of the pressure sensors. If installation a common residential system, the test have the right to be performed and also verified in around 15 minutes. Performing this test will certainly again choose up some additional moisture that will not have to be removed during the evacuation process. Once releasing this high pressure gas perform not relieve the push all the means to atmospheric. Take it it under to around 1 psig. Therefore air can not get back into the system.

Test your Vacuum Pump (Blank turn off testing)

Attach the micron gauge straight to the vacuum pump via the 1/4" connection and verify the the pump is qualified of achieve a vacuum level that 100 microns or less. A great quality pump will easily achieve levels or below 50 microns. Pump blank offs are well known for leaking, so execute not count on one because that isolating the vacuum pump. Use core tools to isolation the pump and also the hoses therefore minimizing any chance of gas permeation v the hoses. Remember also the finest vacuum rated hoses will leak and that is why isolation is a necessity. If her pump cannot attain 100 microns or less, change the oil through a high quality, short vapor push oil favor Appion Tezom. Plenty of times several oil alters are forced to remove far-ranging amounts of moisture from a wet pump. Contrasted to system breakdown, oil is cheap change it often. If the pump will still not attain a deep vacuum, it may be time because that replacement or service.

Notes ~ above Gas the Ballast (If equipped)

Water can only be eliminated from a system in vapor form. If the environment that you are removing native the refrigeration device is moisture laden, as that humidity enters the pump the is in vapor form, that is in a state of equilibrium through the waiting in the system. This state of equilibrium is what is intended by the ax ballast. (something that gives stability)The ballast, once it is open introduces cost-free air into the pump throughout the discharge hit to keep this humidity in equilibrium. If the gas ballast is closed, the pressure created in the discharge stroke will certainly condense the water vapor and also drop the moisture out into the oil. Having the ballast open throughout the early pull down of a wet mechanism will assist to prevent condensation in ~ the pump. (keep it open until you are at 15,000-10,000 microns,) humidity is what kills the vacuum pump oil. Once oil is wet, the vapor pressure boosts to a point where a deep vacuum deserve to not be created. (wet oil is white oil) If the oil is wet, the is cheaper and also faster to adjust the oil climate to let the gas ballast work it out. The moisture will also damage your pump if left in therefore always change the oil if you are work-related on a wet system. The reason I introduce you always readjust the oil is it is difficult to see exactly how cloudy is is with a little unlit vision glass. An open gas ballast avoids the pump from reaching its ultimate vacuum levels and also should it is in closed after ~ you with 15,000-10,000 microns. The gas ballast supplied used only throughout the roughing period and only necessary when there is humidity in the system. One of the most essential things you have the right to do is to always nitrogen sweep or purge a system before performing one evacuation. This method push the nitrogen v the system, one side to the following WITHOUT substantially raising the device pressure. This will push out the moisture vapors v out dropping lock out right into the device in fluid form. If girlfriend purge throughout assembly, and also sweep the mechanism with nitrogen before evacuation, friend will likely not need to use the gas ballast in ~ all. The gas ballast is only effective in removing little amounts that moisture, for this reason a really wet system will require regular oil changes if you desire to make fast work of obtaining the task done.


A/C & Refrigeration systems room designed to operate with only oil andrefrigerant flowing through them. When a usual system is mounted and/or serviced, air and also moisture enter the system. Oxygen, nitrogen andmoisture (all make up our wait or atmosphere) are detrimental to system operation. Removal of the air and other non-condensibles is called degassing and also removal the the humidity dehydration. Removed of both is commonly referred to as evacuation.

Assuming the valve cores are removed, connect big diameter vacuum rated hoses come the earlier of the core devices (do not use side ports of the core device for evacuation) at both the high and also low next of the device so the both sides deserve to be pulled under simultaneously. While at very first it may seem respond to intuitive to use big diameter hoses the value rapidly becomes noticeable after starting the evacuation. 1/2" hoses will certainly decrease the time compelled for evacuation through a aspect of 16 times end the common 1/4" hoses supplied by most of the industry. Larger hoses mitigate friction and therefore rise conductance speed. The conductance rate of 1/4" hose is so tiny it need to never be supplied for evacuation. If girlfriend can, protect against 1/4" hoses because that evacuation together they space too time consuming and costly to it is in effective. Connect the hoses directly to the vacuum pump with a brass flare tee or v a vacuum rated manifold. Perform not usage manifolds that room not equipped with o-ring seals as packing regularly holds under pressure but leaks in a vacuum. Keep relationships to a minimum and points of access to the maximum. In other words, connect to as many places together you can on the system yet eliminate unneeded hoses or fittings. If just two clues of access are available, attach directly to the vacuum pump eliminating the need for a manifold.

Install a high high quality vacuum gaugewith a copper line or brass connectordirectly to the core set up on the suction line. This will permit the evacuation rig (hoses and also fittings) come be totally isolated from the system throughout the "standing pressure tests" whereby the quality of the vacuum will be measured.

Start through fresh and dry vacuum pump oil. Vacuum pump oil is exceptionally hygroscopic (moisture absorbing) so starting fresh will certainly make points go a lot faster. If your pump is equipped through a gas ballast, open the ballast till a level the 10,000 microns is reached. Within narrow limits, the objective of the vacuum ballast is to protect against water vapor indigenous condensing in the pump during the discharge punch of action. Generally speaking the is far better and faster to change the oil fairly than to wait because that the gas ballast to eliminate excess humidity from the oil during pump operation. Moisture destroys vacuum pump oil by enhancing its vapor pressure so much that a high level of vacuum can not be created. The pump cannot develop a higher vacuum then the vapor push of that sealant. If in doubt readjust it out!

1st was standing Test

Pull a vacuum till a level of 1000 microns is reached, (if using huge diameter hoses and also core tools, evacuation the the line set and evaporator coil will take less than 15 minutes for a usual residential device of approximately 5 tons). Isolate the vacuum v the main point tools allowing the

pump to proceed to run and also record the leak rate (after around a 5 minute stabilization period) indicated by the vacuum gauge if equipped. Leak price is simply acquired from a drop in vacuum over a unit that time, commonly displayed in microns per second. A climb in the pressure after a short stabilization duration indicates there is still moisture in the mechanism or the presence of a small system leak.

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2nd standing Test

Open the core devices and permit the mechanism to continue the evacuation process until the vacuum level is 500 microns or less. Then repeat the "standing test" to identify of over there is a diminish in leak price after the stabilization the the vacuum. If over there is no leak, the 2nd leak rate in the device the leak rate should be substantially less than the very first indicating development in the task of dehydration.

Telling the Difference in between Moisture and also a system Leak

If the leak rate has actually not decreased, two things might be happening: