TW-357 REV E
20
Control Operation
This section of the operating manual is for Taylor-Wharton approved equipment that uses the
KRYOS controller.
Introduction
The KRYOS temperature and LN2 level controller is designed for easy operation and uninterrupted,
reliable service. This controller will maintain the selected temperature and liquid level range of LN2
in your refrigerator as well as provide audible and visual alarms for any alarm conditions that may
occur. An
“alarm”
is any off-normal condition, such as a sensor short or open circuit, a temperature
outside of the limit set by the user, or any other condition that would cause the controller to enter the
ALARM
mode.
“Events”
are lid openings and closings, solenoid valve openings and closing, and
operation of the controller’s relay for remote alarm indication.
“Data”
refers to periodic alarm and
event logging available at the
“Data Output”
connection.
The KRYOS controller should require no additional attention to control temperature and maintain
liquid level if an adequate supply source of liquid nitrogen is maintained. If your protocol calls for
you to “top-off” the cryostorage system at the end of a workday or workweek, press the FILL
button. The unit will fill to the upper allowable liquid level and stop automatically. You may choose
to manually stop the fill by pressing the STOP button at anytime during the fill.
Normal Fill Cycle
When the refrigerator is filled and the controller is operating, the LOW LEVEL and LOW ALARM
sensors are immersed in liquid nitrogen. Their resistance values are interpreted by the controller as
“in liquid”. At the same time, the FULL LEVEL and the HIGH ALARM sensors are above the
liquid pool, sending the controller an “above liquid” signal. As liquid nitrogen evaporates, the liquid
level in the refrigerator drops slowly until the LOW LEVEL sensor is above the liquid and sends a
different signal to the controller. After a delay sufficient to ensure the signal, the controller interprets
this condition as low liquid and opens the fill solenoid, admitting more liquid nitrogen from the
supply source.
The refrigerator will fill slowly. The fill continues until the STOP FILL sensor sends the controller a
signal that it is now in liquid. The controller will close the liquid supply solenoid to stop the fill. As
liquid evaporates, the display will indicate the liquid is at a normal level as the cycle begins again.
The KRYOS temperature and liquid level controller is designed to support a remote alarm.
Connections are provided on the back of the controller chassis.
Power
The control can be turned on and off by pressing the Power button followed by “42”, as instructed
on the display panel. The two-step shutdown is a precaution against accidental shutdown. Shutdown
can also be password protected to prevent users from turning the system on and off under the
security section of this manual.
