The A2L & Refrigerant Transition - Short #302 · HVAC School - For Techs, By Techs summary

Key takeaways

A2L refrigerant systems incorporate safety sensors and blower recirculation systems to manage flammability risks.
Refrigerant sensors in A2L systems typically use MOS technology and have limited lifespans, requiring proper maintenance and troubleshooting.
Common issues include sensor contamination, damage, or improper installation, leading to system errors or lockouts.
Systems are designed with safety features like isolation valves and pump-down capabilities to contain leaks outside occupied spaces.
Proper understanding and handling of these sensors and safety devices are critical for safe and efficient HVAC system service.
Regulatory standards continue to evolve, adding complexity but enhancing safety in refrigerant management.

Summary

Introduction and Context

The podcast begins with a light-hearted introduction and quickly moves into the main topic of A2L refrigerant systems, specifically focusing on their new safety features, components, and the challenges they present to HVAC technicians. The hosts emphasize the evolution of systems due to regulatory changes and the importance of understanding the new safety devices such as refrigerant sensors and blower recirculation systems.

Refrigerant Safety Devices and Sensors

The episode discusses the purpose and function of refrigerant sensors in A2L systems, which detect refrigerant presence within the space or control cabinet. The focus is on blower recirculation systems (BRS) that activate the blower to dilute refrigerant concentrations below flammability limits, enhancing safety. The sensors often use MOS technology, have limited lifespans, and may require troubleshooting when faulty. The conversation covers how these sensors communicate with the system, troubleshooting tips, and the importance of understanding their operation for safe system servicing.

Challenges and Troubleshooting in the Field

The hosts highlight real-world issues such as sensors tripping due to contamination (e.g., VOCs, aerosols), improper installation, or sensor damage. They mention common symptoms like fans running without compressor engagement and how to diagnose these problems—particularly by checking sensor status and related safety controls. Additionally, systems equipped with isolation valves and pump-down features are discussed, illustrating safety measures to contain refrigerant leaks outside the occupied space.

Sensor Technologies and Future Considerations

An overview of sensor technologies used in A2L systems is provided, including MOS sensors and sound wave-based sensors. The lifespan and susceptibility to contamination of these sensors are discussed, along with their communication methods, such as modbus or simple relay signals. The hosts underscore the importance of proper handling, installation, and the impact of sensor failure on system operation, especially in larger commercial and VRF applications that incorporate additional safety components.

Regulatory and System Design Impacts

The podcast covers how new standards (like UL 60335-2-40) and safety requirements influence system design, such as adding SSOVs and external sensors. They note how these safety features increase complexity but are crucial for preventing flammable refrigerant-related incidents. Troubleshooting now involves checking sensors and safety controls, with emphasis on understanding system lockouts and the importance of proper sensor replacement.

Conclusion and Education

The hosts wrap up with a reminder about the importance of understanding these new technologies to prevent safety hazards and system downtime. They encourage ongoing education and awareness of evolving safety devices and system components in the HVAC industry.

Show notes

In this short podcast episode, Bryan and Roman talk about the A2L & refrigerant transition again, particularly sensors on R-454B and R-32 equipment.

Since the beginning of the A2L transition, we have seen the equipment evolve and begin requiring accessories, including refrigerant sensors and blower recirculation systems (BRS) or dissipation boards. In a BRS, the blower turns on and dilutes the refrigerant in the space to keep the refrigerant concentration below the lower flammability limit (LFL) and prevent ignition. Some systems may also have isolation valves and pump themselves down whenever the A2L sensor trips. These sensors use MOS technology, which measures gas changes by tracking electrical connectivity shifts; they have limited lifespans and can become corrupted over time.

In the field, you may notice a running fan without the outdoor unit running. Some diagnostic boards might give you error codes, but if you don't and don't have 24V when you troubleshoot the issue, you may want to check the sensor. The sensors could be wet, tripped by VOCs, or even have been cut out.

This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, TruTech Tools, Fieldpiece, and Filtrete.

Resources

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The A2L & Refrigerant Transition - Short #302