How to Calculate Deans Switch Restrictor Sizes for GC and GC/MS

shannon Thanks for your insightful video. While we are using Deans switch for allowing the flow either through restrictor (solenoid v/v-OFF) or secondary column (solenoid V/V-ON), we are using PSD in 8890 or PCM in 7890 for supplying the gas for flow diversion from primary column to either direction and also to supply make up flow to restrictor/secondary column. 

Could you please explain, how do we choose this aux pressure value in method. In case of PSD what should be the pressure and purge flow?

I don't recommend running the columns on a Deans Switch in pressure control mode.  Define the columns for the GC and run the columns in flow control mode and let the GC decide what that pressure is.  A good starting point is Column 1 should be about 80% of the flow of Column 2 or Restrictor.   If you see peaks splitting across both channels then you either do not have the flow balanced across the restrictor by not choosing the appropriate restrictor dimension, you have a leak somewhere on the Deans Switch, or you do not have enough secondary flow to activate the pressure switch cleanly (in that case increase the flow on the secondary column).  This is the troubleshooting logic you should use with a Deans Switch.

I don't recommend running the columns on a Deans Switch in pressure control mode.  Define the columns for the GC and run the columns in flow control mode and let the GC decide what that pressure is.  A good starting point is Column 1 should be about 80% of the flow of Column 2 or Restrictor.   If you see peaks splitting across both channels then you either do not have the flow balanced across the restrictor by not choosing the appropriate restrictor dimension, you have a leak somewhere on the Deans Switch, or you do not have enough secondary flow to activate the pressure switch cleanly (in that case increase the flow on the secondary column).  This is the troubleshooting logic you should use with a Deans Switch.