EPA has begun limiting the use of refrigerants that have high global warming-potential properties. The refrigerant manufacturing industry has responded by developing a number of replacement refrigerants. One of the characteristics of most of these products is that they are minimally flammable as compared to other flammable refrigerants. Different protection schemes exist for lesser risk products which are not as restrictive as those for other more flammable refrigerants. The change addresses a new class of refrigerants with lower flammability characteristics called Group A2L refrigerants. This change simply allows Group A2L refrigerants in refrigeration machinery rooms to comply with the current code requirements for Group 1, Division 2 electrical systems, OR install detection and ventilation systems to mitigate the hazard.
The IFC, IMC, and ASHRAE have historically classified refrigerant flammability as:
Group 1 (nonflammable)
Group 2 (moderately flammable), and
Group 3 (highly flammable
The newly developed and environmentally preferred refrigerants present a lower flammability hazard than traditional Class 2 refrigerants; therefore, a new classification, Group 2L, was established.
In addition to flammability, refrigerants are classified as either nontoxic (Group A) or toxic (Group B). The new refrigerants are primarily classified as Group A2L—nontoxic, mildly flammable. The 2L refrigerants have a burning velocity of less than 10 cm/sec when tested in accordance with ASHRAE Standard 34, “Designation and Safety Classification of Refrigerants.” The energy required for ignition is very high, and the subsequent pressure rise after ignition is much less than refrigerants with higher flammability characteristics. IMC Table 1103.1 (Refrigeration Classification, Amount and OEL [Occupational Exposure Limit]) recognizes 2L refrigerants as a sub-class of Group 2. Historically, ammonia was the only widely used refrigerant with these burning characteristics. The IFC and other codes recognize this, and have made a number of exceptions for ammonia. These exceptions are based on the fact that its burning characteristics reduce the risk of ignition, and the risk of damage if ignition does occur is greatly reduced. These risks are further reduced by code requirements for early detection and ventilation to dilute the ammonia concentration in air. Detection and ventilation approaches are similar to many other hazardous operations, including repair garages, hazardous materials storage and use, compressed gases, corrosives, and other hazardous materials. This is a common and accepted mitigation scheme within the IFC and other codes.
The ventilation rates included in Table 606.17.2 are based on research that shows those rates will maintain a safe environment when more than 90 percent of the refrigerant is released by a leak.
605.13 Mechanical ventilation exhaust. Exhaust from
mechanical ventilation systems serving refrigeration machinery rooms containing flammable, toxic or highly toxic refrigerants, other than ammonia, capable of exceeding 25 percent of the LFL or 50 percent of the IDLH shall be equipped with approved treatment systems to reduce the discharge concentrations to those values or lower.
Exception: Refrigeration systems containing Group A2L complying with Section 605.17.
605.16 Electrical equipment. Where refrigerant of Groups A2, A3, B2 and B3, as defined in the International Mechanical Code, are used, refrigeration machinery rooms shall conform to the Class I, Division 2 hazardous location classification requirements of NFPA 70.
Exceptions:
1. Ammonia machinery rooms that are provided with ventilation in accordance with Section 1106.3 of the International Mechanical Code.
2. Machinery rooms for systems containing Group A2L refrigerants that are provided with ventilation in accordance with Section 605.17.
605.17 Special requirements for Group A2L refrigerant machinery rooms. Machinery rooms with systems containing Group A2L refrigerants shall comply with Sections 605.17.1 through 605.17.3.
Exception: Machinery rooms conforming to the Class I, Division 2 hazardous location classification requirements of NFPA 70.
605.17.1 Refrigerant detection system. The machinery room shall be provided with a refrigerant detection system. The refrigerant detection system shall be in accordance with Section 605.8 and all of the following:
1. The detectors shall activate at or below a refrigerant concentration of 25 percent of the LFL.
2. Upon activation, the detection system shall activate the emergency ventilation system in Section 605.17.2
3. The detection, signaling and control circuits shall be supervised.
605.17.2 Emergency ventilation system. An emergency ventilation system shall be provided at the minimum exhaust rate specified in ASHRAE 15 or Table 605.17.2 Shut down of the emergency ventilation system shall be by manual means.
605.17.3 Emergency ventilation system discharge. The point of discharge to the atmosphere shall be located outside of the structure at not less than 15 feet (4572 mm) above the adjoining grade level and not less than 20 feet (6096 mm) from any window, ventilation opening or exit.