HET-­‐190 – ESL Support TYPE I Study Guide page 1 TYPE I Temperature-­Pressure Chart (also called a T/P Chart or a P-­‐T Chart) 1. Temperatures on the chart are in degrees Fahrenheit (°F). 2. The chart has pressures above and below atmospheric pressure (0 psig). 3. Pressures with an asterisk (*) and a gray background are in inches of mercury (in. Hg) vacuum. All other pressures are in pounds per square inch gauge (psig). 4. psia = psig + 14.7 psi 5. Values on a P-­‐T chart are correct only for saturated refrigerant vapor. This means that refrigerant liquid and vapor are both present in the system or container. Equipment 6. An “appliance” (i) contains CFC or HCFC refrigerant and (ii) is for household (home) or commercial (business) uses. 7. A “small appliance” is charged at the factory with no more than 5 lb. of refrigerant. 8. Examples of “small appliances” are (i) home refrigerators and freezers, (ii) room air conditioners (including window units and PTACs), (iii) packaged terminal heat pumps, (iv) dehumidifiers, (v) under-­‐counter ice makers, (vi) vending machines and (vi) water coolers. 9. “Small appliances” can be serviced only by Type I and Universal certified technicians. 10. Service hoses must have “low-­‐loss” fittings to prevent the loss of refrigerant. 11. All appliances must have a service aperture or device for adding or removing refrigerant. 12. “Small appliances” usually have a piece of straight tubing (process stub) that can be pierced (punctured) by an access valve. 13. Test recovered refrigerant for non-­‐condensables before re-­‐use. Non-­‐
condensables are gasses from the air (nitrogen, oxygen and water vapor) that can enter a system. 14. To test for non-­‐condensables, compare the pressure of the container with the pressure indicated on a T-­‐P chart. Be sure the temperature has stabilized. The pressure should agree within a few °F of the temperature of the container. ;<)=>?)
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23. Recovery devices for small appliances made before November 15, 1993 must be able to recover 80% of refrigerant whether or not the appliance’s compressor is operating. 24. All recovery/recycling machines made after this date must be certified to meet EPA requirements. 25. Machines made after this date must be able to recover 90% of refrigerant when the compressor is operating or achieving a 4 in. Hg vacuum. HET-­‐190 – ESL Support TYPE I Study Guide page 3 26. Equipment made after this date used to recover refrigerant for disposal must recover 80% if the compressor is not operative and 90% of the compressor is operative. 27. If EPA regulations change after a technician is certified, it is the technician’s responsibility to comply with all changes in the law. 28. After November 14, 1994, only EPA-­‐certified technicians are allowed to buy refrigerant. 29. Any EPA-­‐regulated refrigerant released while filling a graduated charging cylinder must be recovered. (There is a picture of a graduated charging cylinder in your textbook on p. 198, Fig. 10-­‐15.) Recovery Basics – Type I 30. The refrigerant used in a system is stated on the unit’s dataplate. Always check this first before recovery. 31. A vacuum pump cannot be used to recover refrigerant. 32. If a system’s compressor is operating, recover refrigerant through a single connection to the high side of the system. 33. A system-­‐dependent (passive) recovery system can be used on a system whose compressor is not working. Connect recovery hoses to both high and low sides for faster and more efficient recovery. 34. The recovery container must be standing upright. It must be properly evacuated so it is free of non-­‐condensables. 35. The recovery machine will develop excessive discharge pressure if (i) the recovery container has not been properly evacuated or (ii) if the inlet valve of the recovery container is not open during recovery. 36. Cool the recovery container during refrigerant recovery. 37. During recovery, heat the compressor and strike it with a rubber mallet to help free entrapped refrigerant. rubber mallet 38. On systems with capillary tube metering devices, the capillary tube can become plugged (blocked or stopped-­‐
up). If this happens, liquid refrigerant will accumulate on the high side. Therefore, connect system-­‐dependent recovery devices only to the high side. 39. Never mix different refrigerants. They cannot be separated later. HET-­‐190 – ESL Support TYPE I Study Guide page 4 40. Recovery devices should be checked daily with a refrigerant leak detector. Recovery Precautions 41. Install temporary recovery fittings only on copper or aluminum lines. Leak test them before recovering refrigerant. 42. Temporary fittings must be removed after refrigerant recovery to prevent leaks. 43. Schrader valves should be regularly checked for leaks. Replace them if damaged. Cap them after servicing. 44. Sight glasses are not used as fill-­‐limit devices. 45. If you smell a pungent (sharp) odor when a system is opened, it might mean that acids are present due to a compressor burnout. The tubing may need to be flushed. Safety 46. Wear a self-­‐contained breathing apparatus (SCBA) anytime you enter a room where a large refrigerant leak has occurred. 47. If SCBA is not available, ventilate the space and leave the area. 48. If a system is not completely evacuated: (i) compressor head pressure can rise and (ii) moisture + heat + refrigerant + oil  HF (hydrofluoric acid) and HCl (hydrochloric acid). 49. Never heat refrigerant with an open flame or live steam. Poisonous phosgene gas can be formed. 50. DOT regulations require that shipping papers state the total number of cylinders in a shipment. 51. Nitrogen should be used when brazing a Type I (small) appliance. The nitrogen tank should have a pressure regulator.