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This is the first of a 2-part episode in our "CO2 Unfiltered" series covering what causes compressor failures and how to prevent them, featuring Jonas Linnemann, Vice President of Technology at Vitalis. Jonas explains why oil return is more challenging in CO2, and covers topics like primary vs secondary oil circuits, separator efficiency and compressor oil carryover. He also shares practical service and maintenance tips that will help refrigeration techs prevent recurring compressor failures.

In this episode, we discuss:

(01:34) Why Oil Management Matters

(03:34) Booster System Basics

(04:47) Common Oil Misconceptions

(09:20) Viscosity and CO2 Solubility

(15:21) Primary vs Secondary Oil Circuit

(19:59) Reading P&IDs

(23:16) Oil Return Overview

(24:57) Strainers and Maintenance

(27:19) CO2 Separator Cartridges

(29:03) Differential Pressure Checks

(32:39) Oil Carryover Troubleshooting

(36:40) Cartridge Blowout Warning Signs

(40:57) Contamination in Regulators

(44:34) Cartridge Change Procedure

(47:35) Evacuation and O-Ring Tips

Helpful Links & Resources:

Jonas on LinkedIn

Vitalis

Episode 390. CO2 Oil Management (Part 1): Lubrication Basics, Oil Selection, Testing, and Troubleshooting with Alessandro Silva of Bitzer

Episode 330. Oil Issues in Refrigeration Systems

Episode 124: CO2 System Oil Management: Insights from Adam Chapman of Westermeyer Industries

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This is the second of a 2-part episode in our "CO2 Unfiltered" series where we're joined by Massimo Pellizzari, Senior Commissioning Engineer at Daikin, for an in-depth look at Daikin's two-stage CO2 condensing units (link to Part 1 below). Here, we cover wiring, as well as troubleshooting via the onboard display and buttons, alarm code structure, and conditions like wet operation, high-pressure switch trips, and how the controller can detect overcharge or refrigerant shortage. This 2-part episode is packed with practical insights to help technicians work more faster and more confidently with CO2 condensing units.

(00:36) Power Supply Wiring Basics

(05:44) High Pressure Switch Cutout

(07:07) Reading Alarm Codes

(08:38) Wet Operation and Superheat

(14:21) Expansion Valves for High Pressure

(17:50) Piping Diagram and Valve Locations

(19:49) Subcooling Charts and Charge Errors

(23:40) Recovering or Adding Charge Safely

(26:17) Service Access Basics

(27:56) Backup Modes

(31:44) Setpoints and DIP Switches

(33:52) Piping Logic and P&ID

(37:22) Isolating and Purging CO2

(39:45) Oil Loss and Recharging

(40:55) Valve and Sensor Diagnostics

(47:33) Install Tips and Cleanliness

Helpful Links & Resources:

Massimo in LinkedIn

Daikin

PART 1: Episode 418. Daikin 2-Stage CO2 Condensing Unit Servicing and Troubleshooting with Massimo Pellizzari (Part 1)

Episode 14. What About Condensers in Refrigeration Applications?

Episode 394. Condensing Unit Checkpoints

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This is the first of a 2-part episode in our "CO2 Unfiltered" series where we're joined by Massimo Pellizzari, Senior Commissioning Engineer at Daikin, for an in-depth look at Daikin's two-stage CO2 condensing units. Massimo explains the design philosophy behind these systems, how they differ from traditional refrigeration equipment and the best practices for installation, commissioning, evacuation, charging and servicing. Whether you're new to CO2 or looking to sharpen your troubleshooting skills, this episode is packed with practical insights to help technicians work more faster and more confidently with CO2 condensing units.

In this episode, we discuss:

(03:10) Why CO2 condensing units are becoming more common worldwide

(05:30) Daikin's two-stage CO2 condensing unit lineup

(07:15) Swing compressor technology and compressor design

(09:45) Oil in CO2 systems

(11:45) Two-stage compression and reducing discharge temperatures

(17:30) Controller features, monitoring and diagnostics

(24:00) Refrigerant charge calculations and piping design software

(33:30) Factory testing, vibration protection and installation considerations

(38:30) Service valves, access points and system maintenance

(49:30) Pressure testing and evacuation procedures

(50:55) Opening EEVs and solenoid valves during evacuation

(51:00) Refrigeration-grade CO2 and refrigerant purity

(53:10) Proper CO2 charging procedures and overcoming the triple point

(57:30) Service ports, valve design and final technician tips

Helpful Links & Resources:

Massimo in LinkedIn

Daikin

Episode 414. Breaking the Stigma and Learning to Love CO2

Episode 180: Developing your CO2 Knowledge into Experience

Episode 146: CO2 Technical Training with Brett Wetzel

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This episode includes highlights from a recent live Refrigeration Mentor Community meetup where we covered real-world CO2 rack issues, system tuning, troubleshooting, and startup strategies, sharing practical techniques we've learned in the field. We covered gas cooler fan tuning, transcritical operation, oil separator maintenance and service valve tips. This meetup featured experienced CO2 technicians Patrick Gregory, Noah Walker, Andrew Freeburg, Billy Carlson and others sharing valuable insights that can help fellow technicians diagnose problems faster, improve system performance, and learn from the experience of others.

In this episode, we discuss:

(02:15) Fine-tuning CO2 racks

(05:20) Gas cooler fan control strategies

(09:00) Rack tuning

(12:00) Why every CO2 system requires its own tuning strategy

(16:00) Oil separator filter replacement and diagnosing oil trip issues

(18:00) Proper rack pump-down procedures

(20:00) Service valve troubleshooting

(23:45) Common ball valve issues

Helpful Links & Resources:

Episode 382. Why Techs Get Stumped on Supermarket Racks (How To Fix It)

Episode 250. Service Call Stories and Troubleshooting Tips with Andrew Freeburg

Episode 163. A Pro's Handbook for Effective Refrigeration Troubleshooting

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This episode is the first of a 10-part "CO2 Unfiltered" series, where we're joined by Ernesto Rodriguez to discuss hermetic CO2 pumps. Ernesto has decades of practical knowledge to help technicians understand how CO2 pumps really work and why so many failures can be prevented through proper design and installation. Here, we cover pump selection and sizing, and troubleshooting, including how to recognize cavitation and flash gas, avoid common piping mistakes, optimize pump performance, and commission CO2 pumps with confidence.

In this episode, we discuss:

(01:15) Introduction to CO2 pumps and why they matter

(04:50) Internal vs. external recirculation systems

(09:20) Pump construction and hydrostatic bearing lubrication

(15:45) Variable frequency drives and operating at the correct pump curve

(19:20) Recirculation rates and cascade system applications

(24:15) Pump sizing fundamentals, NPSH, and avoiding cavitation

(33:45) Flow regulation, differential pressure regulators, and system balance

(46:30) Installation best practices, suction piping, elbows, and insulation

(55:00) Proper pipe sizing and maintaining flow velocity

(01:01:15) Multiple pump installations and preventing turbulence

(01:09:15) Startup, commissioning, and maintenance checks

(01:12:30) Troubleshooting cavitation, flash gas, vibration, and pump failures

Helpful Links & Resources:

Ernesto on LinkedIn

Episode 285. CO2 Experts: Transitioning to CO2 as a Service Technician Q & A with Andrew Freeburg

Episode 243. Step-By-Step Walkthrough of a CO2 Service Call with Patrick Gregory

Episode 227. Getting to Know Transcritical CO2 Supermarket Refrigeration Systems with Kevin Mullis

Learn more about Refrigeration Mentor Customized Technical Training Programs at www.refrigerationmentor.com/courses

Join the Refrigeration Mentor Hub here

In this episode, we're teaching advanced brazing and soldering skills for copper piping with Mike Belanger from the Copper Development Association. Mike teaches soldering and brazing fundamentals: proper cutting, reaming, cleaning, minimal fluxing, full insertion, correct heat application. This session also covers vital tips for how to properly braze starting with the foundations of what refrigeration techs need to know and how to make better joints and prevent leaks.

In this episode, we discuss:

(05:57) Soldering Basics

(11:17) Six-Step Joint Soldering Method

(15:42) Capillary Space Science

(18:31) Heat And Filler Technique

(20:00) Avoiding Voids And Leaks

(27:45) Brazing Method

(34:30) Flux Temperatures And Torches

(37:09) Torch Tip Sizing

(38:10) 3T Penetration Rule

(39:23) Fillet Shoulder Strength

(40:41) Braze Test Breakdown

(44:29) Annealing Pressure Derating

(48:29) Nitrogen Purging Essentials

(51:25) Dissimilar Metals and Flux

(55:13) High Pressure CO2 Piping

Helpful Links & Resources:

DOWNLOAD: The Copper Tube Handbook

Episode 20. Refrigeration Piping...Who Knew

Episode 108: CO2 Refrigeration High Pressure Copper Fittings with Tal Gutbir

Episode 386. CO2 Piping

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In this episode, we're talking about how techs are breaking the common fears and apprehensions around CO2 refrigeration as it grows and systems become more controls-heavy. I'll share my own early intimidation with CO2, including having to call for senior help. We'll discuss how learning critical CO2 refrigeration pillars like P&IDs, wiring diagrams, I/O schedules, and refrigeration schedules will help techs get more comfortable with CO2 and learn faster.

In this episode, we cover:

(00:48) My First CO2 Wakeup

(04:56) Training Gaps in the Refrigeration Industry

(06:40) Investing in Yourself

(09:16) Field Diagnosis Mindset

(09:56) Using P&IDs and Prints

(13:34) Owning Your Career Growth

(16:35) Group Learning Opportuities

(20:43) Training the Next Generation of Techs

Helpful Links & Resources:

Episode 369. The CO2 Mindset Shift: How To Get Past The Fears

Episode 370. Training Technicians Who Think, Not Just Fix with Billy Carlson

Episode 201. Removing the Fear of CO2 Refrigeration with Andrew Freeburg

Learn more about Refrigeration Mentor Customized Technical Training Programs at www.refrigerationmentor.com/courses

Join the Refrigeration Mentor Hub here

In this episode, I'm breaking down my 4-pillar framework used in my supermarket and CO2 refrigeration training programs. These pillars include understanding system design, electrical, the input and output (I/O) schedule, and the refrigeration legend/schedule. Building your refrigeration knowledge on these pillars is critical for technicians to identify what's normal, verify issues systematically, and solve harder problems faster.

In this episode, we cover:

01:52 The 4-Pillar Refrigeration Mentor Framework

02:55 System Design, P&IDs and Piping Schematics

03:50 Electrical Systems, Metering and Wiring Diagrams

05:03 Input and output (I/O) Schedules

06:47 Refrigeration Schedule/Legend (Normal Operation)

08:35 How to Diagnose Issues Faster

Helpful Links & Resources:

DOWNLOAD: Refrigeration Mentor Playbook (click here)

Episode 395. Basics of Refrigeration: Importance of Revisiting the Fundamentals

Episode 299. Basic Refrigeration 101

Episode 3. Introduction to CO2 Refrigeration

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Join the Refrigeration Mentor Hub here

This episode is a replay of a recent Refrigeration Mentor Community Meetup where we helped fellow techs with some technical CO2 refrigeration troubleshooting. The live group discussed a problematic CO2 store with high superheat, recurring low-temp oil issues, phase-loss/current-imbalance alarm and others. You'll hear solutions, tips and advice from the fellow techs on the call, including Mikaela Law, Patrick Gregory, Andrew Freeburg, Billy Carlson, Noah Walker, and others. Interested in joining the next meetup? Click here and join our FREE Refrigeration Mentor Hub.

In this episode, we cover:

(01:39) High Superheat and Injection

(03:20) Liquid Line Drop and Flashing

(05:14) Pulse Valve Orifice Fix

(08:10) Oil Logging

(14:41) Pressure Differential and Port Sizing

(19:34) HP Valve Failure

(23:46) Ice Cream Frost Airflow Hack

(26:44) Designing a Custom Divider Prototype

(28:39) Selling Value to Customers

(32:54) VFD Phase Loss Troubleshooting

(35:37) Drive vs Compressor Diagnosis

(38:46) Bypass Tests and Amp Imbalance

(40:08) Using Bitzer Software

Helpful Links & Resources:

Episode 378. Field Stories: Compressor Failure, Case Freeze-Up Troubleshooting, and Electrical Safety

Episode 360. Get Curious on Service Calls (For Faster Troubleshooting)

Episode 382. Why Techs Get Stumped on Supermarket Racks (How To Fix It)

Learn more about Refrigeration Mentor Customized Technical Training Programs at www.refrigerationmentor.com/courses

Join the Refrigeration Mentor Hub here

In this conversation, I sit down with Supermarket Refrigeration Technician Jacob Decker to discuss how newer technicians can land opportunities and gain experience faster. Jacob shares how he moved from residential work and tech school into commercial refrigeration and a full time career with Walmart through connections, overcoming fears, learning form mistakes, and how he benefited from mentorship and structured training. We also cover common challenges for new techs, plus practical habits to build that will fast track the learning curve and open up so many opportunities for building your career in the industry.

In this episode, we discuss:

(01:19) Breaking Into Refrigeration

(02:44) First Commercial Job Lessons

(05:42) Biggest Surprises and Challenges Entering Refrigeration

(07:20) Learning from Mistakes

(12:39) Mentorship and Generational Shifts in the Trades

(16:10) Common Pitfalls for New Refrigeration Techs

(18:32) Building ConfideEpisode 186: How To Attract Young People To The Refrigeration Trade (20:40) Checklists

(25:08) Future Refrigeration Tech and CO2

(26:47) Work-Life Balance in Refrigeration

(28:35) Building Better Work Habits

(34:42) Mental Health in the Trades

Helpful Links & Resources:

Episode 85. Generation Z with love2hvac

Episode 186: How To Attract Young People To The Refrigeration Trade With Rusty Walker

Episode 190. Turning Mistakes Into Lessons and Accelerating Your Refrigeration Career with Andrew Freeburg