Operation
Polycold Cryochiller
Operating the Polycold Cryochiller with a Cryocoil
Installation and Operation Manual
Brooks Automation
6-10
214072 Revision B
Operating the Polycold Cryochiller with a Cryocoil
Start and Cool the System
1.
Follow the System Boot/Power-Up and Compressor Startup procedures in the previ-
ous section.
2.
Switch the unit to Standby using the HMI or remote control.
3.
Monitor the temperature indicated by Coldest Liquid (TC # 4).
•
TC # 4 monitors the temperature of the refrigerant in the coldest part of the
stack and is a good indicator of when to switch to Cool mode.
•
For quick cooling when switching to Cool, TC # 4 should be 5 -10°C colder
than the desired cryocoil temperature. See
NOTE:
The unit may be operated indefinitely in Standby.
If the unit is off for more than 12 hours, it may take up to 30 minutes after going into Standby
to attain complete precooling.
4.
Once the unit has cooled to the desired temperature, the circuit may be switched to Cool mode any
time after the vacuum chamber has achieved vacuum. Most users switch to Cool at crossover
when opening the high vacuum valve. The cryocoil will start capturing water vapor within 60 sec-
onds.
NOTE:
Experiment to determine the shortest pumpdown time for each application.
The sooner the unit is switched to Cool, the faster the vacuum chamber's pumpdown time
will be. However, switching too soon may cause the cryocoil to capture too much water
vapor causing the cryocoil's apparent surface temperature to rise and limit the ultimate
attainable base pressure.
NOTE:
You can use a relay contact from a vacuum gauge on your system to control when to switch
into cool. See
Defrost the Cryocoil
Defrost allows the “regeneration” of a cryocoil in preparation for the next vacuum cycle.
1.
Switch the unit to Defrost using the unit's control panel or remote control.
NOTE:
Start Defrost so that the cryocoil is warm before the vacuum chamber reaches atmospheric
pressure. A typical Defrost takes 4 minutes or less. T
he exact time depends upon the
length of the refrigerant line and the size of the cryocoil
.
2.
By default, the unit terminates Defrost when the return temperature of the refrigerant reaches 20°C.
This assures that no additional moisture condenses on the cryocoil from the atmosphere.
The thermocouple and the end point temperature are user configurable if a shortened Defrost cycle
is desired.
