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Some of the following is for an a/c in car.The differences between an a/c in a car & home aren't enough to matter.

Evacuate A/C system
Evacuating an A/C system is the process of pulling the A/C system into a vacuum. This is one of the most critical processes when recharging or servicing any automotive A/C system and often one of the most misunderstood processes.

Vacuuming an A/C system has no effect on cleaning or removing debris or contamination. The only function of pulling vacuum or evacuating and A/C system is to remove all the air from the system. Removing air will also remove any moisture that may be in the system.

Removing both air and moisture is critical to the proper operation of an A/C system. Air is a non-condensable gas. Leaving air in the A/C system will cause excessive high side pressures and lead to poor cooling performance. Excessive high side pressures will also create greater loads on the A/C compressor leading to premature failure. Additionally, moisture in the system, once mixed with refrigerants will create acids that are harmful to the system. Those acids cause internal corrosion of A/C system components. That leads to leaks in A/C condensers and evaporators.

Whenever pulling a vacuum on an A/C system, it’s critical that the vacuum pump used is capable of pulling deep vacuum, typically under 500 microns. In order to determine proper levels of vacuum, a micron vacuum gauge should be used.

Most manifold pressure gauges include a compound pressure gauge for low side pressure readings. The compound gauge allows the gauge to read levels of pressure and vacuum. The problem is that the vacuum scale on the compound gauge is so small that it is really difficult to tell what level of vacuum is really being attained. Besides, inches of mercury are not as accurate for measuring vacuum as microns.

Microns are only a different scale of measurement. One micron equals one millionth of a millimeter. When comparing levels of vacuum in microns and inches of mercury, understand that 28.9 inches of vacuum is only equal to about 25,000 microns. On the other hand, 29.9 inches of vacuum is almost 50 microns. The lower the number of microns means the better level of vacuum.

When using just compound pressure gauges, it is almost impossible to tell the difference between 28.9 and 29.9 inches of vacuum. What complicates matters even more is that you need to understand water will not boil until a level of vacuum under 1,500 microns is achieved. The vacuum scale on a compound pressure gauge can not assure you that the proper level of deep vacuum is being pulled. For those reasons, vacuum pumps should routinely be checked with a micron vacuum gauge in order to assure that they are pulling the deep vacuum that is required whenever servicing auto A/C systems.



© Copyright 2006 by yourACauthority.com

Home HVAC System....

"must use a micron gauge to show you that the system will hold below 500 microns for 15 minutes. (If moisture remains in the system the gauge will climb from 500 to 1500 microns and stop. If it climbs past 1500 microns there is a leak.) If the tech does not use a micron gauge then there is no way of knowing that all the moisture has been removed. If you do not remove all the moisture then you could end up replacing the compressor again soon."

Receiver Drier

Not to be confused with accumulators, the receiver drier is a metal container that performs a few different functions on the A/C system. Most importantly, the drier will absorb moisture from the refrigerant.

Also referred to as a receiver-dehydrator, the drier is located on the liquid line of the A/C system, just after the A/C condenser and before the expansion valve. The drier not only dries refrigerant, it also filters the refrigerant and stores it under certain operating conditions.

The most common design in use today includes what is referred to as a ‘sandwich’ style filter element. That filter design includes layers of filter media to trap particles of debris and contamination in the A/C system as well as silica gel desiccant that will absorb moisture. As the refrigerant in the A/C system circulates, it will all pass through the drier. Upon entering the drier, the refrigerant is forced through the sandwich style filter in order to reach the pick up tube (at the bottom of the drier). Once at the pick up tube, the refrigerant exits the drier and moves downstream to the expansion valve. On days with reduced heat load, where there is less of a demand on liquid refrigerant in the evaporator, the receiver drier will store some refrigerant.

The most important function that the drier performs is to filter and dry the refrigerant. Understand that when moisture and refrigerant mix, a chemical reaction is created resulting in the formation of harmful acids. Those acids corrode the A/C system components (internally). The resulting corrosion is a form of debris and contamination in the A/C system. Receiver driers should be changed every 3-4 years to assure that moisture absorbing silica gel desiccant is not contaminated with excess moisture. Drier should also be replaced whenever changing other major components like A/C compressors.


© Copyright 2006 by yourACauthority.com