Operating instructions

Unit Maintenance
General
On initial start-up and periodically during operation, it will be necessary to perform certain routine
service checks. Among these are checking the liquid line sight glasses, taking condensing and
suction pressure readings, and checking to see that the unit has normal superheat and subcooling
readings. A recommended maintenance schedule is located at the end of this section.
Compressor Maintenance
The scroll compressors are fully hermetic and require no maintenance.
Lubrication
No routine lubrication is required on AGZ units. The fan motor bearings are permanently lubricated
and no further lubrication is required. Excessive fan motor bearing noise is an indication of a
potential bearing failure.
Compressor oil should be standard refrigeration mineral oil such as Suniso 3GS.
Electrical Terminals
DANGER
Electric shock hazard. Disconnect all power before continuing with following
service.
Condensers
The condensers are air-cooled and constructed of 3/8" (9.5mm) O.D. internally finned copper tubes,
bonded in a staggered pattern into louvered aluminum fins. Maintenance consists of routine removal
of dirt and debris from the outside surface of the fins. McQuay recommends the use of foaming coil
cleaners available at most air conditioning supply outlets. Use caution when applying such cleaners
as they can contain potentially harmful chemicals. Care should be taken not to damage the fins
during cleaning. The coils should be thoroughly rinsed to remove any cleaner residue.
If the service technician determines that the refrigerant circuit contains noncondensables, recovery
can be required, strictly following Clean Air Act regulations governing refrigerant discharge to the
atmosphere. The Schrader purge valves are located on the vertical coil headers on both sides of the
unit, at the end opposite from the control box. Decorative panels cover the coil headers and must be
removed for servicing. Recover with the unit off, after a shutdown of 15 minutes or longer, to allow
air to collect at the top of the coil. Restart and run the unit for a brief period. If necessary, shut unit
off and repeat the procedure. Follow accepted environmentally sound practices when removing
refrigerant from the unit.
Refrigerant Sight Glass
The refrigerant sight glasses should be observed periodically. (A weekly observation should be
adequate.) A clear glass of liquid indicates that there is normal subcooled refrigerant in the system.
Bubbling refrigerant in the sight glass, during stable run conditions, indicates that the system can be
short of refrigerant charge. Refrigerant gas flashing in the sight glass could also indicate an
excessive pressure drop in the liquid line, possibly due to a clogged filter-drier or a restriction
elsewhere in the liquid line. See
Table 38 for maximum allowable pressure drops. If subcooling is
low, add charge to clear the sight glass. If subcooling is normal (15 to 20 degrees F) and flashing is
visible in the sight glass, check the pressure drop across the filter-drier. Subcooling should be
checked at full load with at least 70°F (21.1°C) outdoor air temperature, stable conditions, and all
fans running.
64 ACZ / AGZ-BM IMM ACZ/AGZ-4