AAON BL-600 - Manual (Page 16)

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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
pumps 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, 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 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 needle
valve at each of these points to isolate the
pressure. To measure the pressure at any
given point, open the needle valve at that
point and close the other two needle valves.
One gauge is used so that the calibration of
the pressure gauge is irrelevant in the
calculation of the differential pressure.