Beat Leaks with Detection, Notification, and Monitoring
Leak-control programs spur reclamation by keeping refrigerant in the system
The case can be made that recovery and reclamation begins with keeping refrigerants in the system where they belong; refrigerant that leaks out into the atmosphere is never going to be recovered or reclaimed.
Refrigerant leaks are often looked at in the context of their potential climate impacts, but they actually also have an economic impact, an energy impact, and a life cycle cost impact, according to John Wallace, director – innovation, retail solutions, Emerson. For all these reasons, a good leak detection, notification, and monitoring program is essential.
In a presentation during the 2017 AHR Expo, Wallace provided an example of the total cost of refrigerant leaks. Using U.S. Environmental Protection Agency (EPA) calculators, Wallace examined the climate, economic, energy, and equipment impacts of leaks at a hypothetical supermarket chain using these assumptions:
- Yearly calculations;
- A 100-store chain;
- R-404A refrigerant;
- 3,500 pounds (total) on-site;
- A 20 percent leak rate (compared to 0 percent), which equates to approximately 700 pounds of annual leakage; and
- An average cost of $7 per pound for the R-404A.
The direct climate impact was 124,500 metric tons of CO2, equal to more than 24,000 cars or 10,600 homes.
A very low estimate of the annual economic impact for the chain is approximately $500,000, but that was based on the refrigerant alone and did not include technicians’ time or the cost of possible disruptions to the stores’ operations. There also are energy and equipment impacts based on the size of the leaks and how long they go undetected.
In addition, recent changes to the EPA’s Section 608 program lowered the allowable leak rate triggers at which contractors must take action to repair or replace a leaking system.
“The point is, even small leaks really do matter,” Wallace said. “It’s a very good idea to have some programs in place to identify and minimize leakage and to be very proactive in taking care of the equipment.”
THE BENEFITS OF EARLY DETECTION
Early detection of refrigerant leaks is crucial, as the longer a leak persists, the greater the impact it will eventually have (see Figure 1.)
Wallace noted that most refrigeration systems are designed with enough excess capacity to mask any problems associated with a small leak. As the leak persists over time, however, the impact on the system will become apparent. The system’s energy efficiency will likely be impacted first.
“Systems running low on refrigerant are not operating nearly as efficiently as they should be,” he said. “This is about the time liquid level alarms will pick up those triggers, and you’ll know that something is going on.”
At this point, the wise move is to immediately address the leak. By the time the leak has made an impact on system capacity and activated the temperature alarms, the system may be unable to keep up with the load. This could create a hazardous situation. In supermarket applications, for example, it could imperil food safety.
“Once the system reaches this point, and you receive a call that the temperature in the refrigerated cases is going up or the system has gone down entirely, you’ve got a real problem that you have to take care of as an emergency,” Wallace said. “Obviously, it’s much better to stay ahead of the game and fix leaks as early as possible.”
Where are the leaks in refrigeration systems? Pretty much exactly where you’d expect them to be, said Wallace.
According to an EPA study, most leaks occur in a system’s racks, cases, and condensers (see Figure 2). The major causes of leaks were found to be vibration, corrosion, flare nuts, valve fittings, thermal stress, and improper installation techniques.
“It’s important to have an understanding of where and why leaks occur, so you know where to go looking for them,” he said.
DETECTION AND NOTIFICATION
A good leak-control program has three important elements: detection, notification, and monitoring, Wallace said.
The first step is detection, which simply means you have some type of technology in place to detect a leak.
However, detecting a problem without taking any action isn’t really enough, which leads to the next element: notification. This can be something as simple as local notification, such as a buzzer or an alarm to make you aware that a problem exists, or the notification could be connected to a remote system.
“Building automation systems typically have the ability to send out an alarm or allow users to connect remotely, so you don’t have to be on-site to know a problem has occurred,” Wallace noted.
As part of a broader program, notification systems also let you record and track where the leaks are occurring and what actions were taken to address the leaks. This data can be very useful.
“A leak-detection and notification system is going to generate data, so you may as well use that data to help you be proactive in your maintenance or enable your customers to factor some of the findings into their capital replacement budgets,” Wallace said.
The final step in a good refrigerant management program is monitoring, and Wallace concluded with a look at the three major types of leak-monitoring technology: active, passive, and indirect.
An active system is pretty simple. It has tubing that can be run out to the areas where leaks are most likely to occur (racks, cases, and condensers), a pump to pull in air samples, and a “brain” to determine if there’s a leak in that area or not, he said. These systems can be tied to building automation systems and connected to an alarm, as well.
Passive systems are very similar except instead of tubing and a mechanical pump, it uses sensors and electrical wiring.
Indirect systems use existing sensors in place — typically sensors that are part of the building control system — to detect if there is a problem. These systems analyze the trending data and look for values outside of established thresholds.
According to Wallace, the best monitoring system could take advantage of all three of these technologies.
“Each of these systems has its strengths and together can help your system overall,” he said. “Active and passive direct systems are very good at detecting the general location of a leak, while indirect systems can give you a very early indication that there is a problem in the system itself.”
The bottom line is that none of the steps in, or components of, a good leak-detection, notification, and monitoring system are complicated or expensive, and, when used properly, they can all help you keep refrigerant in the system, where they belong.
Publication date: 4/10/2017