As the industry transitions to mildly flammable A2L refrigerants, leak detection has become a priority. Two key areas of focus include both new system installations, as well as refrigerant leaks, that occur after a system is operational.
New air conditioning and refrigeration systems that use A2L refrigerants are now required to be equipped with refrigerant detection systems (RDS). While refrigerant monitors have long been used in mechanical rooms and enclosed spaces housing equipment such as chillers and refrigeration racks, the same technology is now being applied to individual air conditioning and refrigeration units.
These systems not only monitor for refrigerant leaks and initiate system shutdowns, but they may also be required to activate a mitigation response. Every equipment manufacturer must either install these detection systems at the factory or provide field installation kits designed specifically for their equipment. As a result, technicians will encounter a variety of RDS kits in the field. While system designs may differ, they all perform the same core functions.
When a refrigerant leak is detected, the system shuts down to eliminate potential ignition sources, followed by the appropriate mitigation response. For residential and smaller systems that contain less refrigerant, shutdown alone may be sufficient. In refrigeration systems, a shutdown valve in the liquid line and a check valve in the suction line — positioned outside the refrigerated enclosure — are typically required. Larger systems may require additional mitigation steps, depending on refrigerant volume and the enclosed area.
Each installation must be evaluated individually to determine the appropriate mitigation level. ASHRAE Standards 15 and 34 guide this determination.
Leaky Systems
The second key area of focus involves locating and repairing leaks in existing systems. Solid installation practices are key to preventing leaks, and using proper brazing materials and techniques, as well as pressure testing systems before startup, can prevent future issues. Here are some best practices:
- For flared connections, always inspect the mating surfaces for scratches or debris, and ensure proper alignment and tightening;
- Misalignment and overtightening can distort the flare and cause leaks;
- Avoid using utility knives or tools that may damage flared surfaces when removing protective caps; and
- Always remove any debris from the flaring tool and apply a small amount of refrigeration oil during the flare process.
As the saying goes, prevention is the best cure — especially when replacing or installing new units.
Despite best efforts, even properly installed and maintained systems can develop leaks over time. Technicians can spend countless hours tracking down leaks, as some are obvious and easy to find, while others are minuscule and challenging.
Many tools and techniques can help in the field. A thorough visual inspection may reveal oil stains or discoloration, which can point to a leak. Check for sections of piping or distributor tubes that may be rubbing, and inspect areas where piping passes through panels or clamps. The tube sheets at the ends of the condenser and evaporator coils are common leak points due to metal expansion and contraction. These leaks can be difficult to locate and repair.
I’ve had success using a flat punch to gently move the metal around multiple tubes to expose leaks — but first, the leak must be located.
Leak Detection Tools
Electronic leak detectors are more common than ever, and it is important to make sure the detector is rated for the refrigerant in use. Regularly maintain or replace the sensing element or chip as recommended by the manufacturer, and clean any oil or dirt, and replace filters as needed.
Be aware that air movement can displace leaking refrigerant, making the leak appear elsewhere. Start leak checks at the top and move downward, as refrigerant is heavier than air and will fall. Many detectors also offer adjustable sensitivity to help pinpoint leaks. Power on the detector in a refrigerant-free area before use and allow time for calibration and warmup as needed.
Ultraviolet dye is another popular leak detection method; however, some equipment manufacturers do not recommend its use and may void warranties if it’s applied. UV dye must be used in the correct quantity for the system size and refrigerant charge, and take care to avoid spills and contamination during injection. After the dye circulates through the system during operation, an ultraviolet light can be used to locate leaks. Be sure to apply identifying labels to systems where dye has been used.
Despite advances in technology, soap bubbles remain one of the most effective methods for confirming leaks. Available in spray bottles, with brushes, and in low-temperature formulas for freezers, soap bubbles can pinpoint leaks even after detection with electronic devices.
Each technician may have preferred tools or techniques for leak detection, but many reliable methods exist. It’s essential to remain diligent and adapt to each situation.