Low side pressure must not be pressurized to more than?
the low side design pressure
Six classes of leaks?
(1) Standing = detect while system is off (2) Pressure Dependent = detect when system pressure increases (3) Temp dependent = detect with heat of expansion (4) Vibration dependent = detect while system is running (5) Combination dependent = detect with tw
Electronic leak detectors greatest asset and also its greatest weakness?
Why shouldnt Oxygen or compressed air be used to pressurize a system?
oxygen + oil = potential explosion. Because they contain moisture, and moisture reacts with oil in the system to form acids ( organic solids ) R12 R22 R502 R134a will hydrolyze ( a chemical reaction ) with water forming hydrochloric and hydrofluoric acids
List some of the foreign matters that may enter the refrigeration system?
Noncondensable gases and moisture
Can a vacuum pump remove any kind of foreign matter?
can only remove vapor
What does air in the system cause?
acid build up, moisture, and copper plating
What are the only two products that should be circulated in a refrigeration system?
Oil and Refrigerant
In order to remove moisture from a refrigeration system using a vacuum pump, moisture must be in what state?
Which are the best vacuum pumps?
What are two types of vacuum procedures
Deep vacuum and multiple/triple vacuum
What can be done to get water out from under the oil in the compressor
apply heat to compressor crankcase
When evacuating a refrigeration system that has a solenoid valves, what special procedure must be followed?
open solenoid valve manually or electrically
What is todays most accurate deep vacuum gage
How many microns are in 1 inch
Describe method for cleaning up system that has experienced a motor burn.
Change compressor. Monitor both (temporary and permanent) suction and discharge line filter drier pressure drops and checking the new compressor's oil for acid content
What are the advantages of using large gage lines for evacuation
save time and you will not have to disconnect the vacuum pump and switch the hose line to the refrigerant cylinder to charge refrigerant into the system
Why is it important to change the oil on a vacuum pump after each evacuation?
replace contaminated oil
List the main advantages of microfoam leak detection solution over standard bubble solutions
standard bubble solutions dont have the coagulants and wet adhesives that microfoam does. Microfoam will not corrode brass iron
Why is it important to reach and hold a deep vacuum when pulling a vacuum on the system?
250-500 microns. It is important to reach and hold a deep vacuum to ensure that you have gotten rid of moisture/non condensables and that you dont have any leaks
What could an oily dust spot on a condenser indicate
why should a condenser be covered with a sheet before leak checking with an electronic leak detector?
sheet serves as a barrier against outside air movement
leaks that occour only when the unit is in operation
vibration dependent leak
Describe a combination-dependent leak
temperature, vibration and pressure cause the discharge manifold on a semi hermetic compressor to expand and seep gas