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TW-357 REV E
37
• Move the sensor up or down so that the appropriate numbers of sensors are in liquid (read “L”).
• Get back to the KRYOS main screen and the level indicated should match the physically measured reading.
The Sensor Offset, the Start Fill and the Stop Fill can all be set through the KRYOS menu system (MENU, 2).
Removing/Installing the Solenoid Valve
Disconnect only the solenoid valve lead connection from the back of controller board.
To remove the solenoid valve, loosen the compression fitting that connects the plumbing tubing to fill tube.
Unscrew the two (2) mounting screws that hold the solenoid valve to the solenoid bracket. Then remove the
solenoid valve and its associated plumbing. Disconnect the plumbing from the inlet and outlet side of the
solenoid valve.
To install a new solenoid valve, attach the connecting plumbing to the inlet and outlet connections of the valve
using Teflon tape. Attach the compression fitting to the fill tube first and then connect the compression fitting
to the elbow that is connected to the outlet side of the solenoid valve. Position the solenoid valve onto the
solenoid valve bracket and tighten the two (2) mounting screws. Attach the solenoid valve lead connection to
the controller board.
NOTE:
After disconnecting the solenoid valve leads do not pull on wire. The wires are tied and spiral wrapped
together.
Controller Electrical Tests
If a controller is removed from the refrigerator for service, the liquid refrigerant level must be maintained
manually to protect stored product. The fill solenoid valve will be inoperative with the controller removed. A
flexible fill line terminated with a phase separator may be used periodically through the open refrigerator lid to
conduct manual fill operations until automatic operation is restored.
Sensor Probes. The sensor probes used to detect liquid level by Taylor-Wharton controllers are temperature-
sensitive resistors called “thermistors.” Their resistance to electrical current flow changes greatly with their
temperature. The resistance of a typical thermistor used in these controllers varies with its temperature as
follows:
• At Room Temperature ............................................... 2 ohms to 10 ohms
• In Cold Nitrogen Gas................................................. 8 K ohms to 18 K ohms
• In Liquid Nitrogen ...................................................... 18 K ohms to 35K ohms
Controller Logic. The liquid level controllers read the values of the sensors as indications of liquid level. The
function of a sensor, and its value, are interpreted by solid-state logic circuitry to set normal operating, fill, fill
termination, and alarm conditions. In addition, the refrigerator temperature is monitored and an alarm is
triggered if the temperature raises above a pre-determined point. The following values will be interpreted by a
controller as cause for a logic change – either an alarm, or in some cases, a fill or fill termination action.
From cold gas to liquid Resistance greater than 22K ohms.
From liquid to cold gas Resistance less than 16K ohms.
Defective Sensor Resistance greater than 50K ohms, or less that 5 ohms.