ASHRAE Journal - June 2019 - 42

TECHNICAL FEATURE

the situation, a comprehensive rewrite of ANSI/IIAR
2 was completed to consolidate necessary regulations
for safe design of ammonia systems into ANSI/IIAR 2.
Following publication of the resulting edition of ANSI/
IIAR 2-2014, a gap analysis with ASHRAE Standard 15
was conducted to validate ANSI/IIAR 2's suitability to
serve as a standalone design standard for ammonia
refrigeration.
ANSI/IIAR 2-2014 has since been adopted as a reference standard by all U.S. model fire and mechanical
codes. In addition, based on the comprehensive nature
of ANSI/IIAR 2-2014, the 2018 International Fire Code
no longer references ASHRAE Standard 15 for ammonia
systems, and the 2018 Uniform Mechanical Code (UMC)
is proposing to entirely drop requirements for ammonia refrigeration in favor of a mandatory reference to
ANSI/IIAR 2. The UMC change recognizes that ANSI/
IIAR 2 now includes content necessary to serve as both a
code and a standard. The changes made by Addendum
a delete requirements and exceptions that are unique
to ammonia and R-717 and refer users to ANSI/IIAR 2 for
ammonia refrigeration systems.
Addendum d- Addition of Requirements for A2L
Refrigerants Used in Comfort Cooling. Addendum
d was a long-awaited modification of Standard 15 to
incorporate refrigerants with a Class 2L flammability classification, as defined in ASHRAE Standard
34.2 The 2010 edition of ASHRAE Standard 34 added
optional Subclass 2L to the Class 2 flammability classification. Several refrigerants have been classified as
Subclass 2L (refer to ANSI/ASHRAE Standard 34-2016
and addenda). Use of Class 2L refrigerants previously required compliance with Class 2 requirements
per ASHRAE Standard 15-2016 (or earlier editions). A
broader use of Class 2L refrigerants requires a new set
of alternative application requirements. Addendum d
issued new requirements for high-probability systems
used for human comfort applications. Addendum d
did not change how ASHRAE Standard 15 deals with
Class 2L refrigerants in industrial or commercial
applications (yet to be addressed) or machinery rooms
(addressed in Addendum h).
Addendum d, as well as Addendum h, were years in
the making. In 2009, SSPC 15 created a working group to
develop requirements specific to 2L refrigerants. After

many meetings, teleconferences, sweat, tears, blood,
research and investigation, Addendum d was brought
to fruition after two advisory public reviews (APRs) and
four publication public reviews (PPRs).
Addendum d makes use of lower flammability limit
(LFL) values that were published in an addendum to
ASHRAE Standard 34. Rapid refrigerant leak detection
of Class 2L flammable refrigerants, and air movement
to enable rapid mixing of leaked refrigerant, are at
the core of the requirements presented Addendum d.
Recall that the refrigerant concentration limit (RCL)
has a factor of safety of 4 for flammable refrigerants
per ASHRAE Standard 34. That is, when leaked refrigerant is fully mixed in a space, the maximum refrigerant concentration is 25% of the LFL and cannot ignite.
Basic requirements for refrigerant leak detectors were
included in this Addendum d (new Section 7.6.5).
However, just like Thomas the Tank Engine, continual
improvement will happen, with research and development of refrigerant leak detectors being an ongoing
topic. Additional requirements to specify even more
robust and reliable refrigerant leak detection may
occur in the future.
There was a considerable amount of research into
the use of flammable refrigerants that occurred starting in 2015, and that research is continuing. In fact,
more than $5 million was invested by ASHRAE, the
Air-conditioning, Heating and Refrigeration Institute
(AHRI), the U.S. Department of Energy (DOE) and
California Air Resources Board (CARB) to address refrigeration systems using flammable refrigerants. Standard
15 must rely on published research at the time any
addendum is published, and, as such, future changes
may be expected.
Finally, Addendum d relies on product standards for
listed products that use Class 2L flammable refrigerants.
Addendum d does not repeat the detailed requirements
contained in product standards.‡ Product standards are
under development and subject to change. Addendum d
made a reasonable attempt to correlate its requirements
with the details of the product standards as known upon
publication of Addendum d.
Addendum h-Addition of Requirements for A2L
Refrigerants Used in Machine Rooms. Similar to
Addendum d, Addendum h was finalized after roughly a

‡ UL/CSA 60335-2-40, 3rd edition, was approved by ballot on February 4, 2019. Publication would occur after the cognizant safety
standard committee addresses the comments submitted with the initial ballot and a reballot to approve the changes is approved.
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ASHRAE Journal - June 2019

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