In part two of his series on achieving near-zero refrigerant emissions, columnist Robert Johnson provides guidelines on preventative maintenance for chillers.

Operational costs can rise without proper refrigerant management. As refrigerant quality drops, the compressor must work harder, drawing more power. The same applies to inadequate quantities of refrigerant. Over-charged chillers face an even greater risk of compressor damage than undercharged chillers. With such a high value and impact on operations, it is advisable that steps be taken to maintain refrigerant quality and containment to avoid replacement. Refrigerant management should include steps to ensure the refrigerant's quality and to keep the chiller as tight as possible.

Chillers require ongoing preventative maintenance to achieve peak efficiency. Preventing refrigerant from leaking, preventing air from entering, and preserving refrigerant quality all are elements of good chiller maintenance. By maintaining chillers properly and preventing refrigerant leaks, technicians can help keep operating costs down.

Plant personnel should perform monitoring procedures daily to minimize refrigerant discharge into the atmosphere. For machines with refrigerants operating below atmospheric pressure, technicians should check and log the purge system pump-out rate. Other items to be logged daily include system supply and return water temperatures as well as refrigerant temperatures, levels and pressures.

Technicians also should check guide vane operator shafts, seals, joints and rupture disk discharge lines for oil seepage. Negative-pressure machines such as those using HCFC-123 should undergo scheduled purge unit maintenance. Maintenance should include the purge compressor valve plate, oil separator, purge drum and purge condensing coil. Change purge oil and replace purge valve seals per manufacturer's recommendations.

Minimizing oil changes is desirable because refrigerant is dissolved in the oil and could be released into the atmosphere when it is discarded. When the oil is changed, use vacuum recovery units to reclaim refrigerants that otherwise would be lost. In the past, chiller refrigerant oil typically was changed annually. However, the common practice today is to take an oil sample to a laboratory to determine when the oil change actually is required. The laboratory will check the oil for moisture, acid, metals and other contamination. Any technician performing an oil change must be certified to work with refrigerants, and they must dispose of all waste oil in compliance with applicable regulations.

Tube Check

Technicians should inspect and clean chiller condenser tubes annually. Evap-orator tubes on closed systems typically are checked every three years. If the tubes contain interior baffles, the chiller manufacturer should be contacted for information on how to clean the interiors.

Scale deposits are cleaned chemically, typically by a water treatment contractor. Proper water treatment, including chemicals and metering pumps in the condenser line, reduces fouling of chiller water tubes. Cooling tower sumps also must be treated and cleaned. The importance of operating logs cannot be over emphasized, as they can provide early detection of deteriorating conditions, inefficient operation and refrigerant leaks.

Facilities must contain, convert or replace the CFCs in their chillers. Facility operator should not be reluctant to start the replacement or retrofit of their chillers. With increased enforcement activity by the EPA, non-compliance can result in fines and civil penalties of up to $27,500 per day, up to five years federal imprisonment for knowing or willful violations, and up to two years imprisonment for submission of false records.