For years, NFPA 70, the “National Electric Code” has exempted Engine Rooms/Mechanical Rooms for refrigeration processes using Anhydrous Ammonia from having to be Electrically Classified Hazardous Locations (HAZLOC) as long as the room had “adequate ventilation”. The exemption in NFPA 70 has always been sort of vague and referenced the ventilation requirements in ANSI/ASHRAE 15-1994, Safety Code for Mechanical Refrigeration. But that is ALL CHANGING in 2017 as NFPA 70 2017 is now specifying their own Alarm Set Point if a business wants to use the exception. NFPA 70, 2017 will state:
NFPA 70, 2014 states:
Rooms and areas containing ammonia refrigeration systems that are equipped with adequate mechanical ventilation may be classified as “unclassified” locations.
Informational Note: For further information regarding classification and ventilation of areas involving ammonia, see ANSI/ASHRAE 15-1994, Safety Code for Mechanical Refrigeration, and ANSI/CGA G2.1-1989, Safety Requirements for the Storage and Handling of Anhydrous Ammonia.
NFPA 70, 2017 will state:
Refrigerant machinery rooms that contain ammonia refrigeration systems and are equipped with adequate mechanical ventilation that operates continuously or is initiated by a detection system at a concentration not exceeding 150 ppm shall be permitted to be classified as “unclassified” locations.
Informational Note: For further information regarding classification and ventilation of areas involving closed-circuit ammonia refrigeration systems, see ANSI/ASHRAE 15-2013, Safety Standard for Refrigeration Systems , and ANSI/IIAR 2-2014, Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems
As we can see, there are some interesting changes coming in the 2017 edition.
- The 2017 edition ONLY mentions Refrigerant machinery rooms and has deleted the wording “areas containing ammonia refrigeration systems”. Not sure as to why this was revised, but it should have little impact as very few ammonia refrigeration facilities had ventilation systems in “areas containing ammonia refrigeration systems” other than their machinery/engine rooms anyway.
- The 2017 edition will require the mechanical ventilation to either operate continuously OR be initiated by a detection system at a concentration not exceeding 150 ppm. I should point out that those already complying with ANSI/ASHRAE 15-2013, Safety Standard for Refrigeration Systems will have their alarms and activation set at 25 ppm (the TLV of NH3) – well below the NFPA 70 required 150 ppm. But if a process is NOT doing PSM/RMP and NOT following ANSI/ASHRAE 15-1994, Safety Code for Mechanical Refrigeration, NFPA 70 2017 will NOW require that the “adequate ventilation system” that will ensure the room never exceeds 25% of Ammonia’s LEL (i.e. 40,000 ppm) either operate continuously OR be initiated by a detection system at a concentration not exceeding 150 ppm.
- The 2017 edition will also reference ANSI/IIAR 2-2014, Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems instead of ANSI/CGA G2.1-1989, Safety Requirements for the Storage and Handling of Anhydrous Ammonia.
As I stated above, this change in NFPA 70 should have little to no impact on businesses ALREADY complying with PSM and/or RMP. It is the thousands of facilities that will operate below the 10,000 pound PSM/RMP threshold who may decide they do NOT need to follow ANSI/ASHRAE 15-2013, Safety Standard for Refrigeration Systems that will have to at least meet the requirements in NFPA 70 2017.