1104.4.3 Plenums.

Where the space above a suspended ceiling is continuous and part of the supply or return air plenum system, this space shall be included in calculating the volume of the enclosed space.

Section MC 1105: Machinery Room, General Requirements

1105.1 Design and construction.

Machinery rooms shall be designed and constructed in accordance with the New York City Building Code and this section.

1105.2 Openings.

Ducts and air handlers in the machinery room that operate at a lower pressure than the room shall be sealed to prevent any refrigerant leakage from entering the airstream.

1105.3 Refrigerant detector.

Refrigerant detectors in machinery rooms shall be provided as required by ASHRAE 15.

1105.4 Tests.

Periodic tests of the mechanical ventilating system shall be performed in accordance with manufacturer's specifications and as required by the Commissioner of the Fire Department.

1105.5 Fuel-burning appliances.

Open flames that use combustion air from the machinery room shall not be installed in a machinery room.

   Exceptions:

      1.   Where the refrigerant is carbon dioxide or water.

      2.   Fuel-burning appliances shall not be prohibited in the same machinery room with refrigerant-containing equipment or appliances where combustion air is ducted from outside the machinery room and sealed in such a manner as to prevent any refrigerant leakage from entering the combustion chamber, or where a refrigerant vapor detector is employed to automatically shut off the combustion process in the event of refrigerant leakage.

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