Vogt HEC-10, Руководство по обслуживанию

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HEC-Series Service Manual
SERVICE OPERATIONS
10/21/01
9-1
9. Service Operations
Adjustable Blowdown (for clearer ice). A petcock is installed on the overflow from water pump to
provide means for obtaining blowdown from the water tank during the freezing period. This
supplements the blowdown that is discharged during the thawing period through the bypass piping
connected to the drain of the water tank. (See “Automatic Blowdown” below).
The petcock was set at the factory to discharge enough water during the freeze cycle to produce clear
ice. After installation it should be adjusted to the minimum rate required to maintain production of
clear ice and checked after a few days of ice making.
Automatic Blowdown (harvest cycle). A patented feature of this machine is the automatic
blowdown (40) which is provided to eliminate or reduce the necessity for frequent flushing or
cleaning of the water tank (7) to remove accumulated salts or solids in the water as a result of the
freezing action.
A principle feature of the blowdown arrangement is a drain by-pass effect which is initiated during
each thawing period when the water pump is stopped and the water in the freezer tubes returns to the
water tank thereby raising the water level higher than the by-pass piping (40) and causing a portion of
the water to drain from the bottom of the tank (approximately 1 gal/cycle).
The water level, controlled by the float valve (12), regulates the quantity of blowdown during the
thawing period. An optional solenoid valve can be furnished in place of the drain valve to permit
additional if required.
Float Valve (make-up water). The make-up float valve (12) maintains the proper pumping level in
the water tank for ice making. The valve should be set to maintain a water level in the water tank
during the freezing period, so that there will be a quantity of by-pass or blowdown only during the
thaw mode. The water level during the freeze mode should always be below the by-pass piping to
prevent excessive waste of cold water, resulting in loss of ice capacity.
If it should become necessary to clean the float valve, close the stop valve in the make-up water line
to the machine and remove the float valve. After the valve has been cleaned and reinstalled, check to
ascertain if the proper water level is being maintained.
It is advisable to install a large area strainer in the water supply line to protect the float valve from dirt
or solids in the water which would necessitate frequent cleaning. A strainer of 40 mesh screen is
usually satisfactory.
Expansion Valve. The expansion valve was adjusted before shipment and it is rarely necessary to
change this setting.
If considerably less ice than shown in TABLE 11-1 is being produced per discharge, check the water
supply, circulating water pump, water distributors, liquid line valves, refrigerant level, freezer
pressure switch and all other avenues BEFORE changing the factory setting of the expansion valve.