PURGE SYSTEMS
ISSUE:
Purge Units for Chillers.
BACKGROUND:
The basic function of the purge system is to maintain the low pressure
refrigerating system (R-11, R-113, and R-123) free of non-condensable gases
(air) and moisture. Accumulation of non-condensable gases within the system
causes an increase in condensing pressure resulting in loss of operating
efficiency. Moisture in the refrigeration system causes the formation of acids
that can attack the machine's internal components leading to premature failure.
Purges are an important tool for safe operation of refrigeration system and
conservation of refrigerant. They are most commonly found on low-pressure
centrifugal chillers. ASHRAE Guideline 3-1996, reinforces their worth and now
recommends that designers specify purges that "emit less than one part of
refrigerant per part of air as rated in accordance with the methods prescribed in
ARI Standard 580, with the capability of operating while the chiller is idle".
RECOMMENDATIONS:
1. New low-pressure chillers are generally provided with high efficiency purge
systems. However, consider replacing old inefficient systems with new high
efficiency systems. Purging efficiency could be increased from 5 to 10 lb. of
refrigerant to less than 1 lb. of refrigerant per lb. of air purged. Ensure the
unit is ARI certified to Standard 580, and is UL listed.
2. When possible, select new replacement purge units that can be installed
without having to remove the chiller's refrigerant charge.
3. Most currently available high efficiency purge units come with
microprocessor-based controls, data-logging, diagnostic capabilities, and
on-off duty cycling. Ensure the manufacturer's technical support is easily
available in case it's needed. Also, software and control commands shall be
Y2K compliant and manufacturer shall provide any future software updates
required for continued satisfactory operation of the equipment at no
additional cost to the government.
FOR ADDITIONAL INFORMATION:
Contact Satish Sehgal at 202-565-5032, Kurt Knight at 202-565-4980, or Sat
Gupta at 202-565-5268.
26 October 1998
FM-187C-DA92
Previous Page
