Grocery Refrigeration Talk #LIVE

Key takeaways

Understanding the importance of proper defrost management is crucial for maintaining system efficiency in grocery refrigeration.
Replacing only the faulty components, such as TXV screens or relays, is a best practice, avoiding unnecessary system overhauls.
Refrigerant selection involves considering safety, environmental impact, and system compatibility; propane, CO₂, and ammonia are viable options with proper engineering.
Hot gas and electric defrost methods each have their place, influenced by case type and operational requirements.
Service technicians should be familiar with industry standards like Bulletin 90-30 for accurate refrigerant charge calculations across varying ambient conditions.
Future industry trends may include regulations favoring natural refrigerants, emphasizing the need for engineering safety and innovation.

Summary

Introduction and Event Announcement

The episode begins with an introduction to the sponsors and details about a live event scheduled for January 31st and February 1st, 2020, in Claremont, Florida, before the AHR Expo in Orlando. The event focuses on technical training in refrigeration, HVAC, duct design, manual J and D, brazing, soldering, and more, with notable speakers like Jim Bergman, Allison Bales, and others. Registration is encouraged at hvacrschool.com/event.

Main Discussion: Commercial Refrigeration & Common Issues

The hosts and guests delve into grocery refrigeration, discussing frequent service calls, mainly cases running too warm due to issues like frozen coils or backed-up drains. They emphasize the importance of understanding system components such as evaporator coils, drain pans, and the significance of discharge air temperature measurements. The conversation highlights repair practices like replacing only problematic TXV screens instead of entire valves and discusses the types of refrigerants used, including propane and CO₂, along with their safety and climate considerations.

Defrost Methods and Considerations in Grocery Refrigeration

An in-depth discussion on defrost techniques, focusing on hot gas versus electric defrost, especially in open cases. They cover the purpose of running fans during defrost to aid in melting frost and warming the drain pans, as well as the importance of proper defrost cycle settings. Kevin explains the importance of correct defrost termination and the challenges of managing defrost in various case types, highlighting the issues with frost buildup and methods like hot water hot defrost for severe cases.

Component Failures and Troubleshooting Practices

The guests discuss common failures such as stuck relays, clogged screens, and starved coils. They describe procedures for troubleshooting, including pump-down methods and replacing faulty components like fan relays. Emphasis is placed on minimal invasive repairs, such as changing only the defective parts rather than entire assemblies, and the importance of understanding system controls and sensors for efficient servicing.

Refrigerant Choices and Future Trends in Grocery Refrigeration

The conversation explores the viability of various refrigerants, especially propane, CO₂, and ammonia, considering safety, environmental impact, and system efficiency. Nathan advocates for propane as a highly effective refrigerant, emphasizing regulation and safety management, while Kevin discusses challenges like over-regulation and system charging issues. They also talk about the potential for ammonia systems, especially outdoor solutions with containment strategies, and the broader industry perspective on refrigerant evolution.

Closing Remarks and Additional Topics

Towards the end, the hosts touch upon potential future regulations forcing usage of specific refrigerants, and they advocate for engineering solutions to safety concerns. They also mention upcoming podcasts, resources, and encourage listener engagement through subscription links. The episode concludes with a thank you to listeners and a mention of the live event.

Show notes

n this live podcast episode, we have a fun conversation talking with Nathan Orr and Kevin Compass about grocery refrigeration.

The most common types of calls are those where the machine is "not making temp." Usually, the cases can't maintain temperature due to frozen evaporator coils or backed-up drains. On low-temperature/freezer applications, we must rely on electrical or hot gas defrost to mitigate frozen coils.

Hot gas defrost is a complicated but quintessential part of low-temperature grocery refrigeration because the coils easily freeze. The discharge gas has to go to the evaporator coil and merge back into the liquid line; that gas CANNOT make its way to the suction line without causing damage, so the liquid line pressure needs to remain lower than the discharge line pressure. Kevin sometimes recommends running the fans all the time in open cases because the fans aid in the defrosting process, especially when it comes to warming the drain pan.

Another common issue that refrigeration techs encounter is starved coils. Clogged TXV screens often cause starved coils, but we don't usually replace the entire TXV in grocery refrigeration. Instead, we only replace the part that needs replacing (the screen). The same practice applies to other TXV components; we replace only the powerhead if the powerhead has an issue.

Most grocery refrigeration systems use refrigerants that are quite different from residential HVAC refrigerants. Some of the most common refrigerants are propane and carbon dioxide. However, propane is flammable, and CO2 doesn't work very well in hot climates.

Nathan, Kevin, and Bryan also discuss:

Electric vs. hot gas defrost
Walk-in boxes
Bunker cases/coffin cases
Hoarfrost
Water heaters
Defrost termination
Offsets and thermistors
Underground line sets
Charging refrigeration systems for a wide range of ambient conditions
Ammonia refrigerant

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