AAON LZ Series, Installation Operation & Maintenance

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21
Always control the system from the building
management system, or control panel, never
at the main power supply (except for
emergency or for complete shutdown of the
system).
Scroll compressors must be on a minimum of
3 minutes and off for a minimum of 3
minutes. The cycle rate must be no more than
6 starts per hour.
The chiller is furnished with a flow switch
installed on the outlet of each heat exchanger.
This sensor must not be bypassed since it
provides a signal to the unit controller that
water flow is present in the heat exchanger
and the unit can operate without the danger of
freezing the liquid.
Compressor life will be seriously shortened
by reduced lubrication, and the pumping of
excessive amounts of liquid oil and
refrigerant.
Wiring Diagrams
A complete set of unit specific wiring
diagrams in both ladder and point-to-point
form are laminated in plastic and located
inside the control vestibule.
General Maintenance
When the initial startup is made and on a
periodic schedule during operation, it is
necessary to perform routine service checks
on the performance of the chiller and boiler.
This includes reading and recording suction
pressures and checking for normal sub-
cooling and superheat. See the evaporative-
condensed chiller and air-cooled chiller
sections in this manual for specific details.
Chiller Primary Pumping
Primary pumping uses a single pump to move
water (or glycol) through the chiller
evaporator and back to the building. This
pumping package provides a constant or
variable flow of water to the building. The
pump is activated whenever the chiller is
given a run signal.
Water enters the unit through the return water
piping, and then travels through an air
separator to remove any air that is entrapped
in the water. Following this, the water flows
through a suction guide with an integral
strainer. The end of the suction guide is
removable for strainer access. The strainer
assembly is composed of two parts, the
operational strainer and the startup strainer,
(located inside the operational strainer)
which is to be removed 24 hours after startup.
Scroll compressors are directional
and will be damaged by operation in
the wrong direction. High pressure
switches on compressors have been
disconnected after factory testing.
Rotation should be checked by a
qualified service technician at startup
using suction and discharge pressure
gauges and any wiring alteration
should be made at the unit power
connection.
CAUTION
FIELD WIRED CONNECTIONS
Some units may require field wired
connections. Refer to the wiring
diagrams contained within the unit to
identify any components or controls
requiring additional wiring in the field
before placing the unit into service. All
additional field wiring should be
performed by a Factory Trained
Service Technician.
CAUTION