Read NFPA Journal’s detailed feature on the impending change to flammable refrigerants, what it means, and what’s being done.
What if most refrigerators, air conditioners, and commercial cooling cases were filled with propane, or some other flammable material? How would it impact safety and fire protection during installation, maintenance, or especially during a fire?
Those questions, far from being hypotheticals, are what researchers have been hustling to answer.
In 2016, nearly 200 nations agreed to phase out what had until then been the most widely used type of refrigerant—the substances that circulate through cooling systems to absorb heat and cooling the air—because of the compounds’ very high global warming impact. The perfect replacement, however, has not been easy to find. Some are too toxic, others inefficient. The most promising alternatives are a group of compounds that are at least slightly flammable, or in some cases highly flammable. One of the most popular proposed refrigerant alternatives is a substance called R-290 propane, which is favored by some large supermarket retailers for its environmentally friendly qualities and its cooling efficiencies. In November, the Fire Protection Research Foundation published a study assessing the risks of using R-290 in refrigeration used in commercial retail and kitchen settings. The study assessed how flammability risks change when different quantities, or charge sizes, of R-290 are used in appliances. It also looked at possible ways to limit those risks, and variables that might impact potential explosions. On Thursday, March 22 at 12:30 p.m., the Fire Protection Research Foundation will present a webinar on the findings of this study. The instructor, Scott G. Davis, was the report’s lead author.
Currently, flammable hydrocarbon refrigerants like R-290 are limited to a charge size of 150 grams in commercial refrigerators, or about half a cup of liquid; roughly enough to run a small beverage cooler at a supermarket checkout line. Big retailers such as Target, among others, which helped fund the FPRF study, have expressed a desire to increase those charge limits to run larger coolers if it is deemed safe.
The FPRF study, conducted by Gexcon US, used both full-scale testing and computer models to assess risks of R-290 refrigerants. After various simulations, researchers found that charge size, location of the condensing unit, and whether the condensing fan is running or not, are all factors in how often an ignition occurred during a refrigerant leak. Not surprisingly, as more R-290 leaked into the space surrounding the cooler, ignition became more likely, but as the size of the room increased, ignition risk was reduced.
Based on those findings, researchers set to work assessing the likelihood of a fire event in several simulated scenarios, and found that big box stores’ big sizes could help limit fire ignition potential during a refrigerant leak. For example, based on simulations, a leaky refrigeration case with 150 grams of R-290 located in a 441-square-foot kitchen was more likely to ignite than a 1,000-gram charge of R-290 located inside a 9,040 square-foot store, the study found. The former scenario is allowed by current regulation, while the latter is not. In addition to being smaller in volume, kitchens have more ignition sources than stores, which also increased ignition risk, the study found.
The researchers also made several recommendations based on risk factors they found during testing, including: limiting charge size based on the volume of the room where the unit is located; continuously running the condenser fan during a leak; designing refrigeration units with top-mounted condensers; and that equipment within a closed refrigerator cabinet be designed and rated for use in explosive atmospheres.
Areas that warrant further investigation include efforts to establish risk acceptance criteria, as well as collecting more refrigerant leak frequency data, the study found.