One Universal Tech, Three Refrigerants
You are the only Universal-certified technician at a food-processing plant. In one day you must recover 3.8 lb of R-134a from a water cooler, 18 lb of R-22 from a walk-in freezer, and 250 lb of R-123 from a chiller. The plant has one recovery machine rated for R-12/R-134a/R-22, one low-pressure recovery machine, three recovery cylinders (one labeled R-22, one labeled R-134a, one unlabeled), and a scale. A production supervisor asks you to use the unlabeled cylinder for 'whatever is left' to save time.
1. Can you use the unlabeled cylinder as the supervisor suggests?
Read the worked answer
No. Recovery cylinders must be DOT-approved and labeled for the refrigerant they contain. Using an unlabeled cylinder for 'whatever is left' risks mixing refrigerants, making the recovered refrigerant unusable and creating a safety and recordkeeping problem. Put the unlabeled cylinder aside until it is properly identified or evacuated and labeled. Use the R-22 cylinder for R-22 and the R-134a cylinder for R-134a, and use a suitable labeled container for R-123.
2. How should you assign equipment and evacuation levels across the three jobs?
Read the worked answer
The water cooler is a small appliance; recover the R-134a with compatible equipment and evacuate to at least 4 inches Hg vacuum if opened. The walk-in freezer is a high-pressure appliance; use the R-22-rated recovery machine and evacuate to the applicable high-pressure level-10 inches Hg vacuum for a post-1993 appliance, or 25 inches Hg for a pre-1993 appliance. The R-123 chiller is low-pressure; use the low-pressure recovery machine and evacuate to 25 mm Hg absolute. Universal certification lets you perform all three, but it does not make one machine or cylinder suitable for every refrigerant.
3. The R-22 cylinder reaches 80% of its water capacity before the walk-in is empty. What do you do?
Read the worked answer
Stop recovering into that cylinder. Use the scale and switch to another properly labeled R-22 recovery cylinder. Do not exceed 80% of the cylinder's water capacity, and do not mix the remaining R-22 with R-134a or R-123. Record the amounts recovered and keep the cylinders labeled. If no other R-22 cylinder is available, stop the recovery and obtain one rather than overfilling or mixing.