Polycold Cryochiller
Operation
Installation and Operation Manual
Dual Circuit Modes of Operation
Brooks Automation
214072 Revision B
6-7
Dual Circuit Modes of Operation
Each refrigerant circuit in the dual-circuit Polycold Cryochiller functions in the same way as the sin-
gle-circuit Polycold Cryochiller. The only difference is that the refrigerant is split into two separate feed
and return lines so that it serves two cryosurfaces. Both refrigerant circuits can be put into Defrost mode
or Cool Mode or Standby Mode.
When one circuit is in Defrost while the other circuit is in Cool,
the circuit in Cool may warm by a few
degrees, nominally about 5 degrees.
The timing of the Defrost activity may be considered to maintain your process requirements. If the sec-
ond circuit is a baffle for a diffusion pump, this is not an issue. However, when both circuits are used to
cool cryocoils, you must evaluate the impact on your process when you defrost one circuit while the
other circuit is in Cool during a deposition process.
If the refrigerant circuits are operated in different modes, the following will happen.
One Circuit Standby and One Circuit Cool
The cryosurface being cooled will get several degrees colder than when both cryosurfaces are cooled
simultaneously. This is because there is less total heat load on the system. It is not possible, however,
to get 100% of the cooling capacity into one circuit simply by not using the other circuit.
One Circuit Defrost and One Circuit Cool
The cryosurface being cooled may warm by about 20 C degrees. The warming is caused by refrigerant
from both cryosurfaces being combined in the common return line.
One Circuit Defrost versus One Circuit Standby
The cryosurface being defrosted may have a defrost time that is slightly longer than when both cryosur-
faces are defrosted at the same time.
