Purge Unit at the Hospital
A hospital has a 400-ton R-123 centrifugal chiller with a 650-lb charge. The machine runs below atmospheric pressure. The purge unit logs show it has run 40 hours in the past week, up from 2 hours. The chiller still holds capacity, but the operator wants you to 'pull a vacuum on the chiller to check for leaks' using the house vacuum pump, then recharge from a bulk R-123 drum. You are Type III certified and have a low-pressure recovery unit.
1. Why is the operator's plan to use the house vacuum pump for leak checking a problem?
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A low-pressure R-123 chiller already operates below atmospheric pressure, so pulling a deeper vacuum with a house pump is not a valid leak test and can draw air and moisture into the machine. It can also remove refrigerant if the charge has not been recovered, which would be venting. The purge-unit runtime is a sign of air ingress. Leak-check with approved methods such as an electronic detector, ultrasonic leak detector, or dry-nitrogen pressure testing per the manufacturer. Do not use the house vacuum pump as a leak-check tool.
2. If you must open the chiller for repair, what recovery and evacuation requirement applies?
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R-123 is a low-pressure refrigerant, so use the low-pressure recovery unit, not the high-pressure recovery machine. Recover the refrigerant and evacuate the chiller to 25 mm Hg absolute, which is the EPA evacuation level for low-pressure appliances. Do not vent R-123; it is an HCFC and an ozone-depleting substance. Store recovered refrigerant in a proper, labeled container and follow the manufacturer's procedures for moisture control and filter-drier replacement.
3. The operator says another technician has Type II certification and can 'cover' the job. Does that work?
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No. Type II certification covers high-pressure appliances, not low-pressure chillers. This R-123 centrifugal chiller requires Type III certification unless the technician holds Universal certification. Your Type III certification is the appropriate credential, but it does not by itself authorize you to skip recovery, evacuation, or leak-detection rules. The Type II technician cannot legally perform this low-pressure work just because the job is at the same facility.