AAON LZ Series, Installation Operation & Maintenance

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is correct, replace the pipe plug over the
charging valve for protection.
Purge air from system before placing tank
into operation. All models have system water
contained behind the diaphragm.
It is recommended that the pre-charge be
checked annually to ensure proper system
protection and long life for the vessel.
Pressure Relief Valve
Required pressure relief valve is installed in
the unit. This valve is set at 125 psig. Figure
2 shows inlet pressure versus capacity for this
pressure relief valve. See appendix for
additional information.
Figure 2 - Pressure Relief Valve
Automatic Air Vent
There is an automatic air vent installed at the
high point of the system inside the pumping
package compartment. The air vent valve
must be in the proper position for operation.
Ensure that the small vent cap is loosened two
turns from the closed position, allowing air to
be vented from the system. It is advisable to
leave the cap on to prevent impurities from
entering the valve. See appendix for
additional information.
Dual Pumps
When redundant pumping is required, factory
installed dual pumps or two single pumps can
be ordered. A dual pump is a pump with two
independent motors and impellors in a single
casing. This dual pump has a swing split-
flapper valve in the discharge port to prevent
liquid recirculation when only one pump is
operating. Isolation valves in the casing allow
one pump to be isolated and removed for
service while the other pump is still
operating.
When redundant pumping is required with
high flow rates, two independent pumps may
be installed in parallel. Each pump will have
its own suction guide/strainer, combination
valve, and isolation valves.
The controls package will activate the pump
when the unit is given a run command. If the
controls do not recognize flow in 60 seconds
(factory default), the second pump will be
activated and an alarm signal will be
generated. If the second pump does not
activate, the cooling will be locked out. See
Appendix - Water Piping Component
Information for additional information.
Pressure Gauges and Thermometers
Pressure gauges and thermometers are
available as a factory installed option.
Thermometers are installed on the inlet and
outlet of the unit. One pressure gauge is
installed at each pump. This pressure gauge
is connected in three places to the water
piping before the suction guide/strainer, after
the suction guide and before the pump, and
after the pump. There is also a valve at each
of these points to isolate the pressure. To
measure the pressure at any given point, open
the valve at that point and close the other two
valves. One gauge is used so that the
calibration of the pressure gauge is irrelevant
in the calculation of the differential pressure.