4 Evacuation and Dehydration Procedures Free Online FlashCards

How do evacuation and dehydration differ?

Evacuation removes refrigerant, air, and other gases; dehydration removes water vapor and moisture from the circuit.

Does a deep vacuum replace refrigerant recovery or leak testing?

No. A deep vacuum can help dry the system, but it does not replace refrigerant recovery or a leak test.

What must be done before opening the refrigeration circuit?

Recover refrigerant with approved equipment before opening the circuit. Do not vent refrigerant.

What low-pressure recovery level does EPA Section 608 list for qualifying appliances?

For U.S. stationary appliances with more than five pounds of refrigerant, the listed recovery level for a low-pressure appliance is 25 mm Hg absolute. This is not a deep-dehydration target.

Where should the micron gauge be placed?

Use a calibrated micron gauge at the chiller or as close to the system as practical, not at the pump. Hose restriction can make the pump-side reading look better than the system vacuum.

Why pressure-test for leaks before dehydration?

Repair leaks and complete the required pressure leak test before dehydration; a leak can prevent a reliable vacuum.

Why can moisture freeze during evacuation?

As pressure falls, water boils at lower temperatures. Evaporation can cool moisture until it freezes, temporarily slowing drying and making readings misleading.

How is a vacuum-decay test started?

Close the valve between the system and pump to isolate the chiller, then stop or isolate the pump as directed. Record the starting micron reading, time, and system temperature.

What can a rising pressure during a vacuum-decay test indicate?

A rise toward atmospheric pressure suggests a leak; a rise that slows or stabilizes below atmospheric pressure can be consistent with moisture boiling off. A decay test alone cannot conclusively distinguish them.

What gases are prohibited or restricted for pressure testing?

Never pressure-test with oxygen or compressed air. Use dry nitrogen only with a regulator and within the manufacturer's pressure limits.

How should standing water be removed before evacuation?

Remove standing water using the manufacturer's procedure; a vacuum pump is not a substitute for draining bulk liquid.

Can a conventional manifold gauge verify a deep vacuum?

No. A conventional manifold gauge is not accurate enough to verify a deep vacuum.