water level float switch will make, opening the
COOLING
/
MAKE
-
UP
(3/8”) solenoid valve, replacing the
hot discharged water with cooler water.
This unit’s operation is similar to a TW-DI unit except that a VTR unit has a reservoir tank that is open to
the atmosphere, which allows a maximum 180° F
PROCESS
water temperature.
Notes: 1.
The DIN units do not have pressure switches. The y use float switches instead
2.
The make up water level float switch is the higher one in the reservoir tank. The low
water level cut-out float switch is the lower one in the reservoir tank.
3.
Anytime the three phase power is turned on to the unit the cooling/make-up water is
(3/8”) solenoid valve may energize.
The VTR unit operates in either a positive or negative pressure mode. Upon energizing the unit, if the
make-up level float switch is in the made position, the
COOLING
/
MAKE
–
UP
water in (3/8”) solenoid valve
will open and begin to fill the unit’s
PROCESS
piping and reservoir tank. As the water level rises in the
reservoir tank, or if it is sufficiently full to begin with, the low water level float switch will make, turning
off the
(
LOW WATER PRESSURE
)
light on the operator panel.
S
TARTING UP THE UNIT
The start button may now be pressed to energize the unit. The negative pressure mode of operation is
initiated by turning the 3-way valve (See Figure 1.) at the back of the unit counter clock-wise. Negative
pressure in the process piping is caused by diverting some of the flow from the pump through the eductor.
The water bypassed to the eductor creates a high velocity flow at the eductor nozzle which then causes a
suction on the from process line.
Never turn the valve all the way to “negative” (counter clockwise), because all the flow will bypass the
process, and there will be no temperature control of the mold. When the unit is running in a negative
pressure mode, any leak that was in the system will now be drawing air in to the process piping.
The air and water mixture is separated in the separation tank located on the suction side of the pump. The
air is vented from the unit through the overflow connection on the back of the reservoir tank. If this vent
becomes plugged, the unit will not work properly.
1.4
TROUBLESHOOTING A VTR UNIT
A few things may cause the VTR unit to act erratically. If glycol is present in a heavy concentration
within the process water, it may foam and back up into the reservoir tank. This can cause the reservoir
tank to overflow, or the float switches to stick. This problem may be eliminated by using an anti-foaming
agent in the water, and periodically opening the (1”) pipe plugs on top of the tank to clean the switches
with a soft haired paint brush.
An inability to get desired cooling can be a problem with a VTR unit. If the cooling water out line
pressure is greater than the unit’s pump discharge pressure, there is no way for the unit to cool. A change
in the installation will be required in order to provide a reduced cooling water out line pressure.
If the reservoir tank continuously overflows there is a chance that either a float switch has stuck or the
cooling/make-up valve has stuck open from a piece of dirt.
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