8 PFS 155C - 315C OM 135
Electrical Terminals
WARNING
Electric shock hazard. Turn off all power before continuing with following service.
Re-tightened all electrical power terminals for compressors every six months (normal heating and
cooling of the wire may loosen connection).
Refrigerant Sightglass
Observe the refrigerant sightglasses weekly. A clear glass of liquid indicates that there is adequate
refrigerant charge in the system. Bubbling refrigerant in the sightglass, during stable run conditions,
indicates the system may be short of refrigerant charge. Refrigerant gas flashing in the sightglass
indicates an excessive pressure drop in the liquid line, possibly due to a clogged filter-dryer or a
restriction in the liquid line. If subcooling is low add charge to clear the sightglass. If subcooling is
normal 10° to 15°F (6° to 13°C), at full load, and flashing is visible in the sightglass check pressure
drop across the filter dryer.
An element inside the sightglass indicates the moisture condition corresponding to a given element
color. If the sightglass does not indicate a dry condition after about 12 hours of operation, pump
down the unit and change filter-dryers.
Lead-Lag
McQuay PFS water cooled chillers alternate the sequence in which the compressors start to balance
the number of starts and run hours. Lead-lag of the compressors is accomplished automatically by the
MicroTech controller.
When in the auto mode the compressor with the fewest number of starts will be started first. If
both compressors are operating and a stage down to one compressor is required, the compressor with
the most operating hours will cycle off first. The operator may override the MicroTech controller, and
manually select the lead compressor as #1 or #2.
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