1105.6 Ventilation.

Machinery rooms shall be mechanically ventilated to the outdoors. Location of the mechanical ventilation openings within the machinery room shall be based on the relative density of the refrigerant to air. When compressors or self-contained unit system are housed in a machinery space, other than in a machinery room or plenum, the space shall be ventilated in accordance with the requirements of Section 1105.6.3.

   Exception: Where a refrigerating system is located outdoors more than 20 feet (6096 mm) from any building opening and is enclosed by a penthouse, lean-to or other open structure, natural or mechanical ventilation shall be provided. Location of the openings shall be based on the relative density of the refrigerant to air. The free-aperture cross section for the ventilation of the machinery room shall be not less than:

   F = √G            (Equation 11-1)

   For SI: F = 0.138√G

   where:

      F = The free opening area in square feet (m 2 ).

      G = The mass of refrigerant in pounds (kg) in the largest system, any part of which is located in the machinery room

1105.6.1 Discharge location.

The discharge of the air shall be to the outdoors in accordance with Chapter 5. Exhaust from mechanical ventilation systems shall be discharged not less than 20 feet (6096 mm) from outdoor air intake or openings into buildings and 10 feet (3048 mm) from a fire escape or exterior stair.

1105.6.2 Makeup air.

Provisions shall be made for makeup air to replace that being exhausted. Openings for makeup air shall be located to avoid intake of exhaust air. Supply and exhaust ducts serving the machinery room shall not serve any other area, shall be constructed in accordance with Chapter 5 and shall be covered with corrosion-resistant screen of not less than 1/4-inch (6.4 mm) mesh.

   Exception: The requirement for supply and exhaust ducts to the machinery room to serve no other area shall not apply to a change in the type of refrigerant in a lawfully installed existing refrigerating system being maintained and operated in accordance with these approved installation requirements:

      1.   Where the replacement refrigerant has a safety classification of Group A1; or

      2.   Where the replacement refrigerant is R123 and the engineer or architect demonstrates to the satisfaction of the commissioner that providing such air supply and exhaust ducts represents a hardship and that the proposed alternative provides an equivalent level of safety.

1105.6.3 Ventilation rate.

For other than ammonia systems, the mechanical ventilation systems shall be capable of exhausting the minimum quantity of air both at normal operating and emergency conditions, as required by Sections 1105.6.3.1 and 1105.6.3.2. The minimum required ventilation rate for ammonia shall be 30 air changes per hour in accordance with IIAR2. Multiple fans or multispeed fans shall be allowed to produce the emergency ventilation rate and to obtain a reduced airflow for normal ventilation.

1105.6.3.1 Quantity-normal ventilation.

During occupied conditions, the mechanical ventilation system shall exhaust the larger of the following:

   1.   Not less than 0.5 cfm per square foot (0.0025 m 3 /s × m 2 ) of machinery room area or 20 cfm (0.009 m 3 /s) per person.

   2.   A volume required to limit the room temperature rise to18°F (-7.8°C) taking into account the ambient heating effect of all machinery in the room but not above a maximum temperature of 122°F (50°C).

(Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023)

Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.