Taylor-Wharton 24K w/ AutoTend - Manual (Page 20)

est part of the chamber (worst case temperature). Factory installation includes one
thermocouple inside of the sensor tube at an elevation to match the height of standard
racks. A second Type T thermocouple may be added to monitor another location
inside the chamber. Both thermocouples can be activated/deactivated through the
menu system. (MENU, 1,1)
Calibrate Temperature
KRYOS provides easy calibration of the thermocouples. To calibrate, the user should
enter the menu system (MENU, 1,2). Remove the thermocouple from the sensor tube
and dip thermocouple #1 into an ice water bath. The fourth line of the control display
will indicate “Wait” and will give a reading on the proximity of the temperature to 0ºC.
When the temperature reaches equilibrium the control will indicate “OK” and the user
can press the left soft-key button. Dry the thermocouple thoroughly. Next, the control
will prompt you to dip thermocouple #1 into LN
2
. Wait while the control self calibrates
to -196ºC (-320ºF). When it does, the control will again indicate “OK” and the user can
again press the left soft-key button. The control will then indicate that the temperature
has been calibrated. The thermocouple is now ready to be repositioned inside the
sensor tube. Be sure that the thermocouple elevation is well below the lid when
closed. Please note that both thermocouples are calibrated by going through this
process with Thermocouple #1.
Test Temperature System
The temperature circuitry can be checked at any time through the menu system
(MENU, 1,3). This check will tell if the thermocouples are working or if they are “open”
(broken or unplugged). If a thermocouple is not connected to the control it will check
as “open.” If a termocouple is “Disabled” through the menu system, it will not show up
on the check.
Level Sensing
The level sensing in the system is determined through the use of thermistor based
sensor assemblies. Thermistors are thermal resistors whose resistances change as
temperature changes. Their use in liquid level control is a time tested method to
provide accurate results. The KRYOS uses a 7, 8 or a 4 thermistor assembly to
measure liquid level in the freezer. The 4 sensor assembly provides general informa-
tion about liquid level (high alarm, high, normal, and low alarm) while the 7 and 8
thermistor assemblies provide liquid level readings accurate to the nearest inch.
When the LN
2
level drops below the START FILL sensor, the control opens the
solenoid valve to commence the fill process. This process continues until the LN
2
level reaches the STOP FILL sensor. When the control “senses” that the LN
2
has
reached the upper level, it flashes “Check” on the display while the KRYOS insures
that it has not received false signals and then allows the fill to stop. The fill process
can be halted at any time before it reaches the STOP FILL sensor by manually
pressing the STOP FILLING button.
Test Level Sensors
The sensor assembly can be tested through the menu system as well (MENU, 2,1).
The sensor diagnostics indicates the sensor number and the status (whether in liquid
or gas) of that sensor. If the control is set for an eight thermistor or Freeze-Guard
sensor it will indicate 8 sensors in the diagnostics. Likewise, if it is set for a four
sensor assembly, it will indicate 4 sensors. The status is indicated with either an “O”