23
initial startup, the boiler may have to be
cycled several times to generate an adequate
water level.
Makeup Water
A 3/4” FPT city make up water connection is
provided to replace water that is lost from the
system.
Glycol units require a glycol feeder (optional
factory installed or field installed) to replace
fluid that is lost in the system. Water should
not be directly added to glycol applications as
this would dilute the glycol concentration and
thereby increase the freezing temperature of
the fluid.
The makeup water connection is provided
with a backflow preventer that has isolation
valves on the inlet and outlet for service.
Figure 1 shows the pressure drop versus flow
rate for the backflow preventer.
Figure 1 - Backflow Preventer
There is a pressure-reducing valve after the
backflow preventer. This valve reduces the
city water pressure to maintain the operating
pressure of the system. This valve is
adjustable from 10-35 psig with a factory
setting of 30 psig. The system pressure varies
with the height of the system. The pressure-
reducing valve setting should be set so that
the pressure at the high point in the system is
high enough to vent air from the system
(usually 4 psig). There should be air vents at
all parts in the system where air could be
trapped. If the pressure is not high enough
throughout the system, flashing could occur
in the piping or the pump could cavitate.
There is an isolation valve on the inlet and
outlet of the pressure-reducing valve for
service.
The pressure reducing valve fills the system
at a reduced rate. There is a bypass around the
pressure reducing valve for the initial fill of
the system to increase the initial fill speed.
After the initial system fill, this valve should
be closed.
Compression Tank
As the water temperature in the system
increases, the volume that water displaces
increases. In order to compensate for these
expansion
forces,
a
compression
or
expansion tank must be used. The factory
installed tank option includes a pre-
pressurized diaphragm compression tank that
is preset for 12 psig.
The factory pre-charge pressure may need to
be field adjusted. The tank must be pre-
charged to system design fill pressure before
placing into operation. Remove the pipe plug
covering the valve enclosure. Check and
adjust the charge pressure by adding or
releasing air.
If the system has been filled, the tank must be
isolated from the system and the tank emptied
before charging. This ensures that all fluid
has exited the diaphragm area and proper
charging will occur.
If the pre-charge adjustment is necessary, oil
and water free compressed air or nitrogen gas
may be used. Check the pre-charge using an
accurate pressure gauge at the charging valve
and adjust as required. Check air valve for
leakage. If evident, replace the Schrader
valve core. Do not depend on the valve cap to
seal the leak. After making sure the air charge
Summary of Contents for LZ Series
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