When the fridge is in Cold Hold mode, fill it to the Heat-Ex top and let it dry off the liquid in the fridge nose, keeping the material cool. 

Please see the CCP (Cryo-Control parameters) after putting the fridge on Cold Hold mode. 

1. Status of Run and Bypass valves on CCP. 
   
   

Click on point 1, "Fridge Valve," in the above picture to open the VI. Points 2 and 3 show the Run and Bypass valve opening at 0.00 turns in the above picture. 

2. Status of GV bypass opening on CCP. To reduce LHe consumption, you can put the GV bypass opening at 8.1% (make sure the Fridge pressure keeps flat). The target parameters Fridge/1000 (Torr) and Fridge/100 (Torr) should be flat. 

Suppose the fridge pressure is above 100 torr. In that case, the Fridge/1000 (Torr) target parameter and the fridge temperature to the Fridge/1000 (K) target parameter are reliable. Suppose the fridge pressure is under 100 torr. In that case, the Fridge/100 (Torr) target parameter is reliable, and the fridge temperature is the Fridge/100 (K) target parameter. 

In the above picture, open the 'GV Bypass' VI at point 1, and you can adjust the GV Bypass opening to keep the fridge pressure flat and reduce the LHe consumption. 

3. Status of Separator flow on CCP.

In the above picture, open the 'THCD-401' VI at point 1, and you can adjust the Separator flow to reduce the LHe consumption. 

Please see the CCP (Cryo-Control parameters) when the fridge nose level drops and the target material keeps cooling down in Cold Hold mode. 

What if the Target Parameters start increasing: 

If the target parameters increase, crack open the Run valve at 0.55 or 0.65 turns to get the liquid into the fridge nose to keep the target material cool. Please see below how to open the Run valve: