User guide

278 Advanced User Guide
9 Columns and Oven
Cryogenic Operation
The cryogenic valve lets you operate the oven below ambient
temperature. Minimum attainable oven temperature depends on
the type of valve installed.
The GC senses the presence and type of cryogenic valve and
disallows setpoints if no valve is installed. When cryogenic
cooling is not needed or cryogenic coolant is not available, the
cryogenic operation should be turned off. If this is not done,
proper oven temperature control may not be possible,
particularly at temperatures near ambient.
Cryogenic setpoints
Equilibration time Set from 0 to 999.999 minutes.
Cryo [ON] enables cryogenic cooling, [OFF] disables it.
Quick cryo cool This is separate from Cryo. Quick cryo cool cools
the oven faster after a run than it would without assistance.
This is useful when maximum sample throughput is necessary,
however it does use more coolant. Quick cryo cool turns off soon
after the oven reaches its setpoint and Cryo takes over, if needed.
Ambient temp The temperature in the laboratory. This setpoint
determines the temperature at which cryogenic cooling is
enabled.
• Ambient temp + 25 °C, for regular cryo operation
• Ambient temp + 45 °C, for Quick Cryo Cool.
Cryo timeout Cryo timeout occurs, and the oven shuts off, when
a run does not start within a specified time (10 to 120 minutes)
after the oven equilibrates. Turning cryo timeout Off disables
this feature. We recommend that it be turned On because cryo
timeout conserves coolant at the end of a sequence or if
automation fails.
Cryo fault Shuts the oven down if it does not reach setpoint
temperature after 16 minutes of continuous cryo operation.
Note that this is the time to reach the setpoint, not the time to
stabilize and become ready at the setpoint. For example, with a
cool on- column inlet and cryo control in the track oven mode, it
may take the oven 20 to 30 minutes to achieve readiness.