Page 125 - 2018_IMC

REFRIGERATION

1105.6.1 Discharge location. The discharge of the air [F] 1105.9 Emergency pressure control system. Perma-
shall be to the outdoors in accordance with Chapter 5. nently installed refrigeration systems containing more than
Exhaust from mechanical ventilation systems shall be dis- 6.6 pounds (3 kg) of flammable, toxic or highly toxic refrig-
charged not less than 20 feet (6096 mm) from a property erant or ammonia shall be provided with an emergency pres-
line or openings into buildings. sure control system in accordance with Section 605.10 of the
1105.6.1.1 Indoor exhaust opening location. Indoor International Fire Code.
mechanical exhaust intake openings shall be located
where refrigerant leakage is likely to concentrate based SECTION 1106
on the refrigerant’s relative density to air, and the loca- MACHINERY ROOM, SPECIAL REQUIREMENTS
tions of the air current paths and refrigerating machin-
ery. 1106.1 General. Where required by Section 1104.2, the
machinery room shall meet the requirements of this section in
1105.6.2 Makeup air. Provisions shall be made for
makeup air to replace that being exhausted. Openings for addition to the requirements of Section 1105.
makeup air shall be located to avoid intake of exhaust air. 1106.2 Elevated temperature. There shall not be an open
Supply and exhaust ducts to the machinery room shall not flame-producing device or continuously operating hot surface
serve any other area, shall be constructed in accordance over 800°F (427°C) permanently installed in the room.
with Chapter 5 and shall be covered with corrosion-resis- 1106.3 Ammonia room ventilation. Ventilation systems in
1
tant screen of not less than / -inch (6.4 mm) mesh. ammonia machinery rooms shall be operated continuously at
4
1105.6.3 Ventilation rate. For other than ammonia sys- the ventilation rate specified in Section 1105.6.3.
tems, the mechanical ventilation systems shall be capable Exceptions:
of exhausting the minimum quantity of air both at normal
operating and emergency conditions, as required by Sec- 1. Machinery rooms equipped with a vapor detector
tions 1105.6.3.1 and 1105.6.3.2. The minimum required that will automatically start the ventilation system at
emergency ventilation rate for ammonia shall be 30 air the ventilation rate specified in Section 1105.6.3,
changes per hour in accordance with IIAR2. Multiple fans and that will actuate an alarm at a detection level not
or multispeed fans shall be allowed to produce the emer- to exceed 1,000 ppm.
gency ventilation rate and to obtain a reduced airflow for 2. Machinery rooms conforming to the Class 1, Divi-
normal ventilation. sion 2, hazardous location classification require-
1105.6.3.1 Quantity—normal ventilation. During ments of NFPA 70.
occupied conditions, the mechanical ventilation system 1106.4 Flammable refrigerants. Where refrigerants of
shall exhaust the larger of the following: Groups A2, A3, B2 and B3 are used, the machinery room
shall conform to the Class 1, Division 2, hazardous location
1. Not less than 0.5 cfm per square foot (0.0025
3
2
m /s • m ) of machinery room area or 20 cfm classification requirements of NFPA 70.
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(0.009 m /s) per person. Exceptions:
2. A volume required to limit the room temperature 1. Ammonia machinery rooms that are provided with
rise to 18°F (10°C) taking into account the ambi- ventilation in accordance with Section 1106.3.
ent heating effect of all machinery in the room. 2. Machinery rooms for systems containing Group A2L
1105.6.3.2 Quantity—emergency conditions. Upon refrigerants that are in accordance with Section
actuation of the refrigerant detector required in Section 1106.5.
1105.3, the mechanical ventilation system shall exhaust 1106.5 Special requirements for Group A2L refrigerant
air from the machinery room in the following quantity: machinery rooms. Machinery rooms for systems containing
Group A2L refrigerants shall comply with Sections 1106.5.1
Q = 100 × G (Equation 11-2) through 1106.5.3.
For SI: Q = 0.07 × G Exception: Machinery rooms conforming to the Class I,
Division 2, hazardous location classification requirements
where: of NFPA 70 are not required to comply with Sections
3
Q = The airflow in cubic feet per minute (m /s). 1106.5.1 and 1106.5.2.
[F] 1106.5.1 Refrigerant detection system. The machin-
G = The design mass of refrigerant in pounds (kg) in
the largest system, any part of which is located in ery room shall be provided with a refrigerant detection
the machinery room. system. The refrigerant detection system shall be in accor-
dance with Section 605.8 of the International Fire Code
1105.7 Termination of relief devices. Pressure relief and all of the following:
devices, fusible plugs and purge systems located within the 1. The detectors shall activate at or below a refrigerant
machinery room shall terminate outside of the structure at a concentration of 25% of the LFL.
location not less than 15 feet (4572 mm) above the adjoining
grade level and not less than 20 feet (6096 mm) from any 2. Upon activation, the detection system shall activate
window, ventilation opening or exit. the emergency ventilation system required by Sec-
tion 1106.5.2.
1105.8 Ammonia discharge. Pressure relief valves for
ammonia systems shall discharge in accordance with 3. The detection, signaling and control circuits shall be
ASHRAE 15. supervised.

108 2018 INTERNATIONAL MECHANICAL CODE 
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