Always learning something new: 10% open on LLCV at CP4 is too low to maintain a cool LN2 transfer line. 20% is a good value. CP4 was overfilled yesterday and left in PI mode overnight with a lower limit set at 10%. Pump level was reading ~88% this morning so I raised set point from 90% to 92% and the signals from pump level fluctuated sporadically from 78-98% and the exhaust pressure rose to levels around 4-5 psi in PI mode with LLCV close to 100% at times. Conclusion is we're cooling the transfer line with increased LN2 flow so I've left the exhaust bypass valve open temporarily, until transfer line is cool and PI behaves as usual. I removed the flow meter and flex line from CP4 exhaust. Configuration is same as other cryopumps.