4 Recovering Refrigerant from Low-Pressure Appliances

How low-pressure appliances affect service

A low-pressure appliance, commonly a centrifugal chiller, operates below atmospheric pressure in parts of its refrigeration cycle. Air and moisture can leak inward, while refrigerant can still escape during service. Safe recovery requires suitable equipment, protection of the chiller and its water circuits, and verification of the required evacuation level before opening the system.

Equipment and preparation

Use Recovery equipment certified for the appliance and appropriate for its refrigerant and operating conditions. Follow the machine manufacturer’s instructions, including pressure limits and the high-pressure cutout. Use refrigerant-rated, compatible hoses and fittings, and a recovery cylinder rated for the refrigerant’s pressure. EPA Section 608 generally requires certified recovery or recycling equipment for appliances covered by the rule; technicians must have the applicable Section 608 certification to service them.

Before connecting equipment:

• Identify the refrigerant and the chiller’s service connections; do not mix refrigerants in a recovery cylinder.

• Inspect the recovery machine, hoses, fittings, and cylinder for damage. Confirm that the cylinder is suitable for the refrigerant and within its test date.

• Place the cylinder upright and secure it. Use a scale while filling, and never exceed its marked maximum gross weight or applicable filling limits. Label it with the refrigerant type and any known contamination.

• Follow site safety procedures. Refrigerant can displace oxygen, so use appropriate ventilation and personal protective equipment, and keep personnel clear of potential leaks.

Connect and recover refrigerant

Follow the manufacturer’s shutdown and isolation procedure. Identify the components to be serviced and determine whether to recover the entire appliance or an isolatable section. EPA allows recovery from an isolated section when the refrigerant can be isolated to a system receiver.

Connect the recovery machine and cylinder using the manufacturer’s specified arrangement. Check connections for leaks before starting. Use the correct recovery mode, and monitor pressure and cylinder weight throughout the job.

Recover accessible liquid first, which generally speeds recovery, and then recover vapor as well. Operate valves in the sequence specified for the chiller and recovery machine; do not bypass safety controls.

Protect water circuits

During evacuation, circulate water through the chiller or drain it as the equipment instructions require. Water in the tubes can freeze as refrigerant pressure and temperature fall. Do not allow a water-filled chiller to freeze.

Manage refrigerant in oil

Refrigerant dissolved in oil can be released during service. EPA Section 608 test guidance notes that heating the oil to about $130\,^{\circ}\mathrm{F}$ before removal reduces refrigerant release.

For an oil change, the appliance or isolated portion must be evacuated or pressurized to no more than $5\,\mathrm{psig}$ before opening. Alternatively, drain the oil into a system receiver that is brought to that pressure.

Verify the evacuation level

For a low-pressure appliance, the Standard evacuation target is $25\,\mathrm{mm\,Hg}$ absolute, about $28.9\,\mathrm{in\,Hg}$ of vacuum relative to standard atmospheric pressure. Verify the pressure with an appropriate gauge. Under 40 CFR § 82.156, technicians generally must recover refrigerant, including liquid refrigerant, to the required level before opening a covered appliance for service or disposing of it. This target applies whether the recovery equipment was made before or after November 15, 1993.

After reaching the target, wait several minutes and observe whether pressure rises. A rise can indicate that refrigerant remains in liquid form or is boiling out of oil. Continue recovery as needed and recheck the pressure.

Apply repair and leak exceptions

Limited repair exceptions apply only when their conditions are met; they are not general alternatives to full recovery.

• Qualifying non-major repair: If the repair is not major and the appliance will not be evacuated to the atmosphere afterward, bring the low-pressure appliance to $0\,\mathrm{psig}$ before opening it. For refrigerants with boiling points at or below $85\,^{\circ}\mathrm{F}$ at standard atmospheric pressure, do not use nitrogen for this pressurization if it would require later purging. For refrigerants with higher boiling points, use heat as much as possible first; nitrogen may then be used to raise pressure to atmospheric pressure.

• Leaking appliance: If a leak prevents evacuation to the table level, or reaching that level would substantially contaminate recovered refrigerant, isolate leaking components from non-leaking components wherever possible. Evacuate non-leaking components to the standard level. Bring leaking components to the lowest attainable pressure without substantial contamination, but not above $0\,\mathrm{psig}$.

• Oil changes: Follow the $5\,\mathrm{psig}$ procedure described for managing refrigerant in oil.

Disposal, major repairs, and other work that does not meet an exception remain subject to the standard evacuation requirement. Consult the regulation and equipment instructions for the specific job.

Close out safely

Close and disconnect valves in the proper order, cap connections, and record the recovered refrigerant and cylinder weight. Arrange for reuse, reclamation, or disposal under applicable requirements. Do not intentionally vent refrigerant.