Polycold Cryochiller
Appendices
Installation and Operation Manual
Appendix H: Rapid Balance Pressure Check
Brooks Automation
214072 Revision B
12-19
Appendix H: Rapid Balance Pressure Check
Rapid Balance Pressure Check, sometimes referred to as Stack Warm, is a method to rapidly check the
equalized system pressure to confirm proper system charge. Balance pressure is the pressure of the
refrigerant when the compressor is at rest and the suction and discharge pressures have equalized to
the same pressure.
Rapid BP Check is done by rapidly warming the system and then allowing the suction and discharge
pressure transducers to reach equilibrium. Once at equilibrium, the pressure gauge reading is the Bal-
ance Pressure. This pressure is very close to the static pressure and very useful for service purposes.
The amount of time that it takes the system to reach the end of the Rapid BP Check is dependent on
the state of the system, the load of the system, and the temperature and flow rate of the cooling water.
Nominal Rapid BP Check takes approximately 15 minutes. Note that unlike other products, the Polycold
MaxCool Cryochiller does not require 48 hours to reach balance pressure.
The vacuum chamber should be in a vacuum state when operating the Rapid BP Check Mode. Oper-
ating this feature when the cryosurface is not in a vacuum environment may cause excessive heat loss
and the process may not be able to complete.
When Rapid Balance Pressure check is completed, some service functions may be performed. How-
ever, charge removal requires a waiting period of a minimum of 12.
Static Pressure versus Rapid Balance Pressure
Static pressure is different from Balance pressure due to the fact that static pressure requires that the
unit is at rest and at ambient temperature for 48 hours or longer. Balance Pressure and Static pressure
may be different by 5 to 20 psi.
To make Rapid Balance Pressure check more relevant, the user should perform a Rapid Balance Pres-
sure check soon after installation. This value should be recorded for future reference.
Rapid Balance Pressure Check Procedure
1.
Verify the vacuum chamber is in a vacuum state, typically 10
-3
torr or below.
2.
Use the HMI keypad to go to the SERVICE MENU and press “Enter”.
3.
Scroll to the AUTHORIZATION CODE. Press “Enter”.
4.
Enter the authorization code for Security Level 2 (Default Operator Access). Press “Enter”. See
5.
Scroll down to “INIT RAPID BP CHECK”. Press “Enter”.
6.
The system performs a rapid defrost and stops the Rapid BP Check procedure when the endpoint
has been reached.
7.
Wait until the suction and discharge pressure transducers reach equilibrium. This typically takes
about 5 minutes.
Note that the transducers may not read the same value when at equilibrium but may have a slight
offset due to gauge accuracy.
