Thermo Scientific Cryo 740 Series, Руководство по эксплуатации и техническому обслуживанию

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Remote Alarm
Contacts
Warning
The lid must remain open throughout the initial filling of the
storage container. ▲
When electric power and LN
2
have been connected, open the lid and turn
on the power switch to begin filling the unit. Because the unit must go
from ambient room temperature to -196°C, considerable boiling of the
liquid nitrogen takes place, turning into super cooled nitrogen gas which
flows over the side of the open chamber. As this occurs, some frost occurs
around the top of the unit. This is normal during the initial fill with the
lid open and disappears once the unit has stabilized.
The storage container fills until the liquid Nitrogen reaches the high level
setpoint of five inches. During the initial fill, the low level alarm sounds
after 10 minutes unless the low level setpoint is reached. Silence alarm and
continue filling. The alarm clears when the low level is met. If low level
setpoint is not reached in one hour, the low level shutdown alarm activates.
See Section 2.
After the initial fill is complete, close the lid and allow the unit to stabilize
for 8 to 10 hours or overnight before changing the high or low level
setpoints or adding inventory.
Caution Some popping or cracking noises may be heard after the unit is
initially filled, and the lid is opened and closed the first few times. This is
normal and will quickly disappear.
▲
The liquid level controller has provision for a remote alarm system. A set
of remote alarm connections (RJ-11 style connector) are located on the
back of the cabinet (Figure 1-1). The remote alarm contacts are "dry"
contacts requiring the remote alarm system to have its own power supply.
The remote alarm contacts are activated immediately when AC power is
lost, or when the unit goes into high level alarm. The contacts are activated
after a thirty minute delay when the unit goes into low level alarm.
The contacts are marked COM = Common, N.O. = Normally Open,
N.C. = Normally Closed
1-6 7000740r7 Cryo Series
Thermo Scientific
Section 1
Quick Start-Up
Fill Unit
Figure 1-5. Contacts