Blast Freezer Convo, & A Loop Sequencer For EPR Control, And A Cross Over ?? Episode - 543 Audio

Blast Freezer Convo, & A Loop Sequencer For EPR Control, And A Cross Over ?? Episode - 543

CO2 Blast Freezer Startup Chaos + Taming Load-Shed Valves (PID Tuning Without Losing Your Mind)

In this episode of the Advanced Refrigeration Podcast, Brett and Kevin recap a CO2 blast freezer rack startup in Minnesota, including a pump-down system with a flash tank setup and a 45-bar-rated rack that sparked questions. The startup went sideways when an oil reservoir appeared empty, oil was pumped in, a compressor kicked on unexpectedly, hydraulically hammered the high-pressure switch, and blew the compressor relief—spraying oil on Brett—after a TechLab relay locked the oil fill on. They then shift to ongoing work: dual-temp HFC island case startups and troubleshooting an underloaded low-temp rack that short-cycles compressors. Kevin shows how a CDS valve on a loop sequencer was hunting from 0–100% and how reducing P gain stabilized suction, then they discuss load shedding/crossover valves, energy tradeoffs, and practical PID tuning tips like filtering, throttle range, direct vs reverse action, and making one change at a time.