The new U.S. national standard for the safe design of closed-circuit ammonia refrigeration systems, ANSI/IIAR 2-2014, sets the minimum requirements for industry compliance and adherence to American codes and regulations. Refrigeration consultants Star Technical Solutions advise ammonia refrigeration system users to review the revised standard and understand how it will affect the safe design of closed-circuit ammonia refrigeration systems.

The standard from the International Institute of Ammonia Refrigeration (IIAR) is “significantly different to previous versions,” says David Blackhurst, technical solutions director at Star. A voting member of the IIAR board of directors, Blackhurst adds, “This is an essential guide for the safe design and operation of ammonia refrigeration systems. It is the regulatory document of ammonia refrigeration and collates best practice information in industrial ammonia refrigeration from practitioners across the world.”

IIAR covered IIAR2 at several sessions of its 2016 annual meeting, concluding today in Orlando.

Key changes to the new edition include incorporating topics traditionally addressed in other codes and standards. Star Technical Solutions says it is the single most comprehensive standard covering the safe design of closed-circuit ammonia refrigeration systems. The IIAR2 includes ASHRAE Standard 15, Safety Standard for Refrigeration Systems; the Uniform Mechanical Code; the NFPA 1 Fire Code; the International Mechanical Code; and the International Fire Code.

The new standard covers stationary closed-circuit ammonia refrigeration systems. Additions include design and installation considerations affecting construction; standalone sections for each type of component such as compressors, refrigerant pumps, condensers, evaporators, pressure vessels and piping; instrumentation and controls for automated systems; and ammonia detection and alarm systems.

The standard includes some completely new items:

  • A full chapter on the use of ammonia refrigeration machinery. This comprises restrictions on the use of ammonia refrigeration systems based on the occupancy classification of the area where the system or equipment will be located.
  • A system design chapter on the requirements that apply to selecting system design pressures. For example, the minimum low-side pressure is 250 psig; the minimum high-side design pressure for water-cooled and evaporatively cooled systems is 250 psig; the minimum high-side design pressure for air-cooled systems is 300 psig. However, individual pieces of equipment might require higher design pressures. Requirements for the removal of oil from oil pots have been changed such that there is no longer a requirement to temporarily install a rigid-piped connection. Direction for the provision of maintenance and functional testing was added, as well as minimum valve tagging standards for system emergency shutdown procedures.
  • Coverage on refrigeration equipment located in areas other than machinery rooms. Previously, regulations concerning certain types of refrigeration equipment located in areas other than machinery rooms have not been provided. For example, in industrial occupancies, it often is necessary to have evaporators located outside of a machinery room in storage and production areas. This chapter provides minimum safety requirements for locating refrigeration equipment in areas other than machinery rooms.
  • The section on compressors includes a notable change specifying a 0.75" minimum size for relief connections.
  • The chapter on refrigerant pumps provides requirements for refrigerant pumps that which are different from those that are specified for compressors.
  • The condensers section continues to provide requirements for air-cooled condensers and air-cooled desuperheaters as well as evaporative, shell-and-tube, plate heat exchanger and double-pipe condensers.
  • New sections on scraped (swept) surface heat exchangers and jacketed tanks have been added to the evaporators chapter.
  • The pressure vessels' guidance provides the minimum design pressure requirements that are consistent with those described above. It also establishes that the minimum size for a relief connection is 0.75" for vessels that are more than 6" in diameter and 1" for vessels that are larger than 10 ft3.
  • A chapter on ammonia detection and alarms establishes the requirements for detection and system response functions. This chapter standardizes requirements that have historically varied depending on jurisdiction, designer, contractor, supplier and end-user interpretations.

In addition, the standard also contains advisory and practical information from international accepted industry practices.

The American National Standards Institute (ANSI) oversaw the development of the IIAR 2 standard following a series of public reviews and stringent controls set up to ensure the representation of the refrigeration industry consensus.

Reflecting on the response to ANSI/IIAR 2 during its development, Blackhurst said, “We are very pleased with the amount of support shown during the public reviews conducted in the drafting of the IIAR 2 standard revision. Although the process has been lengthy and exhaustive due to the amount of comments from respondents, it clearly demonstrates the industry's commitment to ensuring the safety and reliability of the industrial refrigeration operation environment.”

To receive a copy of the ANSI/IIAR 2 Standard, go to