One of the barriers to the new refrigerants is the recognition of flammable refrigerants in building codes. Codes dictate so much about building construction and what mechanical equipment can be used. There are codes for fire protection, building construction, mechanical systems, and other aspects of buildings; all affect the HVACR system. A good article on the history and scope of building codes can be found in FireRescue magazine. There are hundreds of code adoptions, many on the state level, but in some states on the county or local level. Fortunately, there are not hundreds of different codes; most jurisdictions adopt a national model code which gets updated as frequently as every three years.
The codes that are pertinent to HVACR installations are the mechanical codes and fire codes, as well as energy efficiency codes. We will just deal with the first two here. Often, the state or local adoption of codes can trail the availability of new model codes by many years. This is problematic when new technologies require new codes, as with flammable refrigerants.
The two major model codes are the International Code Council’s series of codes and those of the International Association of Plumbing and Mechanical Officials (IAPMO). The former are adopted by most states, but some (including California) use the IAPMO model codes. These model codes, in turn, reference safety standards developed by others, including ASHRAE and UL. The flow of code development as it affects HVACR equipment is shown below.
The ASHRAE and UL safety standards are now ready or close to being ready to be part of the model code. In the case of ASHRAE 15, Safety Standard for Refrigeration Systems, research on flammable refrigerants has been conducted and changes to the standard have been approved. Some changes deal with the use of HVAC equipment in mechanical rooms where ventilation is readily available and where only trained personnel generally occupy the space. Other changes to the standard focus on the installation of equipment in occupied, ‘high probability’ areas. In those applications it is important, should a leak occur, that the concentration of refrigerant does not get close to its ignition point and that the space is ventilated rapidly.
The pertinent UL safety standards are UL 60335-2-40, Safety: Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers, as well as the equipment standards that address the construction of equipment. As of this writing, the third edition of UL 60335-2-40 is being voted on for approval and could be available later in 2019.
The HVACR industry takes safety very seriously. Behind the ASHRAE and UL standards are years and millions of dollars of research and testing that includes simulating worst-case refrigerant leaks, evaluating the integrity of refrigerant piping joints, and determining methods for estimating safe charge limits.
As mentioned above, the major safety standards that are used in the codes are complete or will soon be. The model codes that will incorporate these standards are at the beginning of their three-year development cycle that ends in 2021. It is expected that the UL standard will be incorporated into this cycle. The ASHRAE standard will have to wait until the next cycle, commencing in 2021 and completed in 2024. This will be too late for some states, like California, where the phaseout of new equipment using high-GWP refrigerants begin before then. In that case, California (and others) can insert the new ASHRAE 15 language into their own states’ codes, even if it does not appear in the model code. States and other jurisdictions have control over their own codes; the model codes are only a suggestion.
Those interested and affected should follow the development schedules of the two main code groups, the International Code Council and IAPMO. Code hearings are long and during the hearing, the opportunity to speak on a code change is very short, so usually only code professionals are in attendance. However, the active participation by those companies that have a stake in flammable, low-GWP refrigerants is very important, if the equipment being designed today is to have a market tomorrow.
So, we are getting closer to allowing the use of A2L flammable refrigerants in HVACR equipment, but the industry will have to remain active in the code revision and adoption process. We will also have to work with state officials, so that the revised codes are adopted quickly by all jurisdictions.
Additional reference:
https://www.energy.gov/eere/buildings/articles/how-are-building-codes-adopted
