Deep Vacuum Dehydration Method

The deep vacuum method of dehydration relies on evacuation alone to remove moisture from the system. A deep vacuum is any vacuum o f 500 microns or less; that is, 29.92 in. Hg vac. or greater. When a deep vacuum is established in a closed system, non-condensibles are reduced to a negligible level. As the pressure is reduced, the boiling point of water is also reduced. As long as the ambient temperature surrounding the system is higher than the boiling point of the internal moisture, it will boil off and be expelled. For example, at a vacuum of about 29.72 in. Hg vac. or 5,000 microns, liquid water will boil anywhere in a system where the temperature is 35 ° F or higher.

pic1 55 Deep Vacuum Dehydration Method

In order to know the system has been adequately evacuated, the final equilibrium pressure of the entire system must be found after the system is pumped down and before it is charged. See Figure SP-3-2. First, the system is reduced to a pressure of about 500 microns or below, then it is isolated from the vacuum pump. The reading on the vacuum gauge/indicator is then monitored to note any change in the level of vacuum in the system. If the indicator shows a pressure rise and the pressure continues to rise without leveling off, a leak exists in the system or the connecting tubing. Locate the leak (SP-1) and repair it.

If the indicator shows a pressure rise but levels off between 1,000 and 2,000 microns, this indicates that the system is leak-tight, but still too wet. A constant reading on the indicator of between 500 and 1,000 microns indicates a leak-tight, dry system.

25. March 2019 by matt
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Purpose — Evacuation removes air and moisture trapped in a refrigeration system by the use o f a vacuum pump. Air occupies space in the refrigeration system, reduces heat transfer, and causes erratic operation. Moisture creates problems o f freeze-up that can result in blocked refrigerant flow. Moisture also combines with oil and refrigerant to form corrosive acid and sludge. All of these conditions can cause system damage or failure.


The vacuum pump creates a pressure differential between the system and the pump. This causes air and moisture vapor trapped in the system at a higher pressure to move into a lower pressure (vacuum) area created in the vacuum pump. When the vacuum pump lowers the pressure (vacuum) in the system enough, as determined by the ambient temperature of the system, liquid moisture trapped in the system will boil and change into vapor. Water will boil at room temperature if it is in a deep enough vacuum. Like free air, this water vapor is then pulled out of the system, processed through the vacuum pump, and exhausted to the atmosphere.

The deep vacuum method and triple evacuation method of system evacuation and dehydration are both used frequently. The deep vacuum method is typically used after a repair was made that required the system charge to be recovered and the system opened. Use of the triple evacuation method is recommended when a system has been especially wet. This can be determined by performing an acid/moisture test on the system refrigerant (SP-5) before or during recovery of the refrigerant. Generally, evacuation and dehydration of a system is performed in the following circumstances:
• After assembly and prior to charging a new field-piped split system, evacuate/dehydrate the low-pressure side and piping. When complete, open the service valves and add refrigerant charge to the system as needed.
• After assembly of a field-piped system, evacuate/dehydrate
the entire system before charging.
• After an installed system is opened to the atmosphere as a result of parts replacement or leak repair.
• When an acid/moisture test (SP-5) shows moisture or noncondensible gas in the system.

22. March 2019 by matt
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Refrigerant Recovery/Recycle Procedure Equipment Hookup

pic1 53 Refrigerant Recovery/Recycle Procedure Equipment Hookup

22. March 2019 by matt
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22. March 2019 by matt
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Refrigerant Recovery/Recycle Unit Method

As part o f the no-venting regulations, the EPA requires that all refrigerant be recovered from a system before the system can be opened for servicing. Recovery o f all refrigerant actually means recovery to levels considered acceptable by the EPA. The acceptable levels of recovery are defined by a set of required levels of evacuation (Figure SP-2-3) that must be achieved when recovering refrigerant from a system, or component of a system, for the various categories of equipment.

When opening any system, except for small appliances, you must evacuate the system to the vacuum level set forth by the EPA. The EPA defines small appliances as those in which the refrigerant is sealed within the unit at the factory and the amount of charge is five pounds or less. An example of a small appliance is a room air conditioner. For small appliances, the system is considered completely recovered when either 90% of the refrigerant is removed if the unit has a running compressor, or 80% of the refrigerant is removed if the unit has a non-operating compressor. Since it is difficult to know when the 80% to 90% levels are reached, for practical purposes, small appliances can be considered recovered to an acceptable level when evacuated to 0 psig {0 inches of mercury).

pic1 51 Refrigerant Recovery/Recycle Unit Method

There are some exceptions to these EPA recovery evacuation levels. If evacuation to the specified levels is not achievable because of leaks in the system, or if recovery to these levels would contaminate the refrigerant being recovered, you must:
• When possible, isolate the leaking components from the rest of the system.
• Evacuate non-leaking components to the required levels, if they are to be opened.
• Evacuate leaking components to the lowest level attainable without substantially contaminating the refrigerant. This level cannot exceed 0 psig.

Recovery of refrigerant from a system to the evacuation levels specified by the EPA requires the use o f a certified refrigerant recovery unit or recovery/recycle unit. Generally speaking, the greater the vacuum pulled by the recovery unit, the higher the probability that a high percentage of the refrigerant is recovered. Most recovery units are capable of recovering refrigerant from a system in either the vapor or liquid state. Many automatically adjust to liquid or vapor recovery so refrigerant is pulled from the system as efficiently as possible. Because there is a wide difference in the capabilities of recovery or recovery/recycle units made by the various manufacturers, you must always follow the manufacturer’s safety and operating instructions for the recovery unit being used to achieve the best results.

When the refrigerant to be recovered is highly contaminated, such as after a compressor burnout, or when liquid refrigerant is being recovered, it is a good practice to install an external filter-drier in the common center hose of the gauge manifold set connected to the recovery unit. Be sure to orient the filterdrier for correct flow direction.

Keep in mind that recovery units are not vacuum pumps and do not provide that function. If the dehydration/evacuation of a system is required, a vacuum pump must be used. Refer to Service Procedure SP-3 for instructions on the dehydration/evacuation of a system.

A recycle unit is used to dehydrate and purify the refrigerant so that it can be returned to the system in a purer condition than when recovered. Always make sure that the unit used is capable of processing the refrigerant you plan to handle. The dehydrating and purifying capability of recycle units varies from one model and manufacturer to another. Most recycle units circulate the refrigerant through a distillation, filtration, and drying process to achieve the desired refrigerant quality.

When recycling is completed, the refrigerant is cleaned, but not necessarily to the manufacturer’s original specifications. Acid/moisture testing of recycled refrigerant should be performed to verify the quality of recycled refrigerant before placing it back into the system. For instructions on how to perform an acid/moisture test, refer to Service Procedure SP-5. Recycled refrigerant can only be reused in the same system from which it was recovered, or another system owned by the same customer.

Before using a recovery unit or recycling unit to process a different refrigerant than was last processed, the recovery or recycle unit compressor oil must be drained and replaced with new oil. All filter driers must be replaced and the recovery or recycle unit must be evacuated. Always make sure to use a recovery cylinder designated
for use with the type of refrigerant to be recovered or recycled.

22. March 2019 by matt
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Refrigerant Reclamation

Reclaiming refrigerant is a distillation process that returns recovered refrigerant to the purity of factory-fresh refrigerant. In order for refrigerant to be classified as “reclaimed,” it must be tested to meet ARI Standard 700. Refrigerant cleaned to meet this standard can be used in any application. Reclamation is a complicated process and is done only at reprocessing or manufacturing facilities. Because of this, reclamation is not a field service procedure.

22. March 2019 by matt
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Refrigerant Recycling

Recycling means to process refrigerant recovered from a system through a cleaning and decontamination process so that it is suitable for reuse. This does not imply that its purity meets the cleanliness specifications for new refrigerants. Recycling is usually performed at the job site or service shop using a recycling unit or a combined recovery/recycle unit (Figure SP-2-2). Recycled refrigerant is only reusable by the owner of the equipment being serviced.

pic1 50 Refrigerant Recycling

22. March 2019 by matt
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Refrigerant Recovery

The recovery of refrigerant removes refrigerant in any condition o f purity from a system or container for storage in an approved external container (recovery cylinder). No processing is necessarily done on the recovered refrigerant. Currently, recovered refrigerant is only reusable if it does not change ownership from the owner of the equipment being serviced.

Recovery of refrigerant from a system is done using a certified recovery unit (Figure SP-2-1) or a combined recovery/recycle unit (Figure SP-2-2). Recovery must be performed:
• Before a refrigeration system can be opened to make repairs.
• Before pressurizing a system for leak testing with a mixture of HCFC-22 refrigerant and nitrogen.
• Before disposing of any system or component containing CFC or HCFC refrigerants.
• When it is necessary to remove excess charge from an overcharged system.

pic1 49 Refrigerant Recovery

22. March 2019 by matt
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Leak Detection Procedure Equipment Hookup

pic1 48 Leak Detection Procedure Equipment Hookup

21. March 2019 by matt
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21. March 2019 by matt
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