Minimizing refrigerant leaks has always been an important goal for owners/operators, system designers, manufacturers, and service technicians of commercial refrigeration equipment. As the transition to the next generation of refrigerants progresses, leak detection will play a variety of critical roles: preserving supplies of legacy hydrofluorocarbon (HFC) refrigerants, maximizing system performance and safety, and minimizing negative impacts to the environment.

In traditional HFC-based systems, refrigerant leaks can cause declining cooling performance and release high-GWP greenhouse gases (GHGs) into the atmosphere. As the U.S. Environmental Protection Agency (EPA) continues to phase down HFC production and consumption, operators of existing equipment will experience rising HFC prices — providing additional motivation to minimize HFC leaks. The next step-downs in this process will be 40% in 2024 and 70% in 2029.

The EPA recently released an HFC Refrigerant Management proposal that outlines a set of requirements that include leak repairs on existing systems, refrigerant recovery and reclamation, and automatic leak detection on new and existing equipment installations containing more than 1,500 pounds of refrigerant. The proposal, which is very much aligned with the EPA’s previous Section 608 provision, would reestablish the EPA’s ability to enforce refrigerant management mandates under the authority granted by American Innovation and Manufacturing (AIM) Act of 2020.

In the next generation of commercial refrigeration equipment and system technologies, detecting and minimizing refrigerant leaks will become even more important. For example, in emerging refrigeration systems, leak detection will often be required to help identify the presence of mildly flammable A2L refrigerants and ensure proper safety management. In systems that use the natural refrigerant CO₂, leak detection is required to maintain optimal system pressures and sense toxic concentrations in occupied spaces.

Regardless of refrigerant or system type, effective leak detection should be considered essential for preserving the refrigerant charges needed to ensure optimal performance:

• Maintaining accurate setpoints.
• Avoiding product loss and degradation.
• Maximizing energy efficiency.
• Minimizing refrigerant replacement costs.

Leak detection strategies with emerging refrigerants

In emerging lower-GWP systems, specific leak detection strategies are needed to address refrigerant characteristics and/or equipment infrastructures. For example, because CO₂ (R-744) has much higher system operating pressures than legacy HFC refrigerants, maintaining optimal refrigerant charge is critical to optimize system performance. Because A2L refrigerants have a “lower flammability” classification, safety standards often require the use of leak detection and other risk mitigation measures in higher-charge remote condensing unit systems.

CO₂ transcritical booster system

Large, centralized systems are typically charged with up to 2,000 pounds of refrigerant. Although R-744 can be toxic in high concentrations, it is usually safe to vent outside due to its low-GWP and zero ozone depletion potential (ODP). In addition to the potential risk to human health of exposure in excessive concentrations in confined spaces, R-744 leaks can potentially impair system performance, degrade perishable product quality, and negatively impact retail operations by:

• Reducing energy efficiencies.
• Starving cases at the furthest location of refrigeration circuits.
• Leading to perishable product damage or loss.
• Incurring unnecessary refrigerant replacement costs.
• Shutting down a refrigeration system.

CO₂ leak detection strategies should be designed for early identification of even small amounts of leaked refrigerant. This is especially recommended in enclosed spaces, near racks in machine rooms and in walk-in coolers and freezers (WICFs). Because R-744 is heavier than air and often undetectable by human senses, sensors should be located near the ground and connected to the leak detection control devices. Leak detection devices should be connected to a CO₂ system control capable of generating alarms and performing a variety of system management functions, including providing early detection of slow leaks, activating isolation and safety shutoff valves, identifying the sources of leaks for accelerated issue resolution, and managing system pressures.

A2L refrigeration

Mildly flammable A2L refrigerants are poised for wider adoption and likely will be used in self-contained or remote condensing and/or distributed systems. A2L refrigerants have varying degrees of lower flammability limits (LFLs), which become a key factor in determining charge limits and evaluating if leak detection may be required.

Per recent updates to the UL 60335-2-89 safety standard, self-contained, factory-charged systems with more than 150 grams of a flammable refrigerant — such as A2Ls and R-290 — must pass Annex CC testing requirements. Self-contained systems must be factory-charged and follow specific protocols and construction guidelines to prevent flammable refrigerant concentrations from surrounding the appliance in the event of a leak (or releasable charge).

As such, leak detection is not required in self-contained equipment that passes Annex CC testing. Otherwise, leak detection may be considered an additional safety measure in applications where gas could potentially form in flammable concentrations and present a safety risk to occupants (e.g., enclosed areas, such as a walk-in cooler).

Per UL 60335-2-89, remote, field-erected distributed systems can have much higher allowable A2L refrigerant charges (i.e., potentially up to hundreds of pounds). Leak detection is one of many safety management and/or risk mitigation methods that could be required in certain systems that meet the safety criteria based on the specific refrigerant LFL, application size and equipment and/or system type, the room volume of the installation location, and the use of additional air circulation and/or ventilation measures.

A2L leak detection strategies are designed to identify the early formation of refrigerant concentrations. When required, leak detection will be located near the ground level next to case evaporators — in enclosed walk-in spaces, on a condensing unit, or on a refrigeration rack. Detectors and sensors are typically set to detect the presence of leaked refrigerant per a defined PPM or at 25% of the LFL (well below a flammable concentration).

The sensor and/or leak detection device is integrated into the case controller to activate necessary risk mitigation measures, such as triggering audible and/or visual alarms, shutting off or isolating refrigerant flow, turning on fans to improve circulation and dilute refrigerant concentrations, and communicating with the system controller to feed data analytics.

Fully integrated leak detection solutions

Whether you’re trying to preserve legacy HFC refrigerants in your current equipment or make the transition to the next generation of lower-GWP refrigerants, leak detection should be an essential component of your refrigeration strategy — and a system requirement in certain cases.