A/C

1. A/C Pressure Test and Evacuation

2. Leak Detection • Leak detection must be done after every repair job. • It must also be done anytime the appliance can not hold vacuum or pressure - like a low charge. • If you are looking for a leak, look for oil spots on the piping at the source of a leak.

3. Leak Test • NEVER use compressed air to leak test. • Compressed air mixed with some refrigeration oil will explode. • Nitrogen is the acceptable method to leak test. • Look for low side test pressure

4. Safety Rules • Always wear safety glasses. • Never use oxygen or acetylene to pressurize a system. • Oxygen will explode on contact with oil. • Never use dry nitrogen without a regulator. • Nitrogen cylinders contain pressures in excess of 2000 psi. • The regulator reduces this pressure to a safe level.

5. Methods of Leak Detection • Pressurized with dry nitrogen (system not operational) • Use soap bubbles to find any leaks. • R22 and Dry Nitrogen • Electronic • Halide • Soap Bubbles

6. Methods of Leak Detection • Normal Operation • Use soap bubbles • Ultrasonic • Electronic • Halide

7. Leak Detection Methods Ultrasonic Older Electronic

8. Leak Detection Methods Ultraviolet Method Halide Torch

9. Leak Detection Methods Nitrogen Pressure Method

10. Electronic Testers • Make sure when you are using electronic testers that the tip is actually over the leak. If the tip misses the refrigerant it will not find the leak.

11. Methods of Leak Detection • Per the EPA Small Appliance Leaks Do Not Have to Be Repaired • If the appliance has under 5 pounds of charge. • If the appliance was charged in the factory. • Leak repair, however small is good and profitable service practice.

12. Leak Test (Running system) • Steps to determine if a leak exists: • Check evaporator for temperature. • Check suction pressure • Check high side pressure (Careful) • Look for oil spots • Look for obvious line breaks • Check the sight glass (Careful)

13. Leak Test (Running system) • Pressure readings alone are not determining factors of a refrigerant leak. • The bubbles in a sight glass are not always indicators of a low charge. Do not rely on this. • New refrigerants may show bubbles in a sight glass with a full charge.

14. Evacuation • Evacuation • The removal of air and moisture from a refrigeration system. • Vacuum • The pressures below atmospheric pressure, indicated by inches of mercury (HG) on a 0 to 30” scale.

15. Evacuation • Noncondensibles • Substances which remain in a gaseous form (state) in a refrigeration system, such as nitrogen and oxygen. • Micron • Unit of pressure measurements in millionths of meters of mercury.

16. Evacuation • Single Stage Pump • Discharges directly into the atmosphere and is capable of pulling down to 1000 microns. • Two Stage Pump • Discharges into a second vacuum and is capable of pulling down to .1 microns.

17. Evacuation • Low Vacuum • Vacuum of 2000 microns or more, obtainable with a single stage pump. • High Vacuum • Vacuum of 2000 to .1 microns which requires a two stage pump. • Deep Vacuum • Reducing the vacuum to between 200 and 50 microns.

18. Evacuation • Reasons for evacuation: • To remove noncondensibles from the system. • To remove moisture from the system.

19. Evacuation

20. Evacuation • Effects of moisture in a refrigeration system: • Ice crystals will form at the metering device, stopping refrigerant flow. • Moisture combined with refrigerants creates acids. • Hydrochloric acid • Hydrofluoric acid

21. Evacuation • Combined with refrigerant oil and heat moisture can create a sludge in the compressor and lines. • Moisture will cause a deterioration of the metal parts inside a refrigeration system.

22. Evacuation • Effects of Air or Non-Condensibles in a refrigeration system: • Increases the discharge pressure • Stays in top of condenser

23. Evacuation

24. Evacuation • Effects of Ambient Temperatures on Evacuation: • Moisture is removed in a vapor state. • Boiling temperature will be reduced as pressure decreases. • Increasing the ambient temperature will decrease the evacuation time.

25. Evacuation • To reach a deep vacuum means the pressure is about 200 to 50 microns. • This is a slow process. • The deeper the vacuum the longer it takes.

26. Evacuation • Checking the Vacuum • Reach the desired vacuum level. • Valve off the system from the vacuum pump and let it stand. • If pressure rises and stops • There is still moisture in the system. • Continue evacuation.

27. Evacuation 4. If pressure continues to rise a leak is present. • Pressurize and leak check. 5. After leak is repaired continue evacuation.

28. Evacuation • Trapped air and moisture: • Moisture may be trapped in the crankcase with the oil. • Either run the crankcase heater to boil off the moisture (best method) • Shake or agitate the compressor (strike with a rubber mallet)

29. Evacuation • Air / Moisture may be trapped under the valves in the cylinder of the compressor • During the charged portion of the triple evacuation bump over (momentarily start) the compressor to release the trapped moisture. • Never start a hermetic compressor under a deep vacuum or motor damage may occur.

30. Vacuum Measurement • Compound Gauge • Not very accurate • Electronic Vacuum Analyzer (gauge) • Measures Microns • 1000 Microns = 1 MM HG. • 759,000 Microns = Atmospheric Pressure

31. System in a vacuum

32. Problems • Sometimes the Schrader access valves can leak due to use and service problems. • Replace core if any doubt.