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©2017 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 59, no. 2, February 2017

By John Bush, P.E., Associate Member ASHRAE; Scott Mitchell, J.D., P.E., Associate Member ASHRAE

About the Author
John Bush, P.E., is senior engineer at Electric Power Research Institute in Knoxville, Tenn. Scott Mitchell is senior engineer – energy efficiency program technical policy at Southern California Edison in Rosemead, Calif.

Changing rules around the use of high global warming potential (GWP) refrigerants have been one of the hottest topics in the HVAC&R industry in the last few years. Following the phaseout of ozone-depleting refrigerants starting in the 1990s, the U.S. EPA, acting under the Significant New Alternatives Policy (SNAP) program, has recently changed the status of certain high GWP refrigerants. In the next several years, refrigerants such as R-404A, R-507A, R-134a, and others will be prohibited for use in some types of new or retrofit commercial refrigeration installations.

Changes are happening at a local level, too: California’s Air Resources Board has recently issued a strategy document proposing aggressive changes, which could include GWP limits as low as 150 for stationary refrigeration and 750 for stationary air conditioning. These limits are challenging to reach with today’s most commonly used refrigerants, some of which are highlighted in Table 1.

Increasingly, natural refrigerants such as ammonia (R-717), carbon dioxide (R-744), and hydrocarbons (such as R-290 and R-1270) are being used to meet the demand for very low GWP refrigeration equipment. Hydrocarbons seem to be the long-term solution for systems such as stand-alone refrigeration applications, where the charge level of flammable refrigerant is small and efficiency is very good. For larger industrial applications, ammonia has long been the refrigerant of choice, but due to toxicity and flammability, its use in large quantities near highly populated areas brings risks that must be accounted for and may add cost.

Carbon dioxide is gaining traction for supermarket refrigeration in the U.S., and current research and development efforts are focused on overcoming efficiency hurdles under transcritical operation, which is a particular challenge in warm climates. Solutions that can use these refrigerants while minimizing the technical and safety challenges associated with their use could open new possibilities in significantly increasing the efficiency of the national refrigeration fleet.

Ammonia is itself subject to restrictions on the federal, state, and local levels. In particular, the U.S. EPA has different regulations applying for site inventory thresholds of 500 lb (227 kg) and 10,000 lb (4536 kg) and requires emergency release notification in the event of leaks exceeding 100 lb (45 kg) in a 24-hour period. Similarly, OSHA requirements apply to ammonia facilities, with additional requirements when exceeding the 10,000 lb (4536 kg) threshold. State level programs are common, too. Most notable (and relevant to the field study discussed here) is California, where the quantity for increased scrutiny is 500 lb (227 kg). Inspections and reporting are required at regular intervals, and compliance audits must also be undertaken at regular intervals.

Further restrictions may be applied at the local level, particularly considering ammonia systems in highly populated areas. For these reasons, ammonia charge quantity reduction is becoming an increasingly hot topic in the industry. Most ammonia regulations were intended to deal with large-charge systems. A number of efforts are currently under way to develop regulations specifically for low-charge ammonia systems that can take advantage of ammonia’s high efficiency while minimizing the risk of harm due to leaks.

 

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Comments

  • 13 Apr 2017 | Cindy Roberts
  • I found the article very interesting. It explained why there had been changes to the requirements or exclusion of refrigerants in household items. It was a technical article written for a layman, which I appreciate. I now understand more clearly the importance of the change.
  • Reply

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