1107.0 Refrigeration Machinery Room Ventilation

Refrigeration machinery rooms shall be provided with a source of outside air for ventilation and removal of rejected heat.

Refrigeration machinery rooms shall be provided with dedicated mechanical exhaust systems. The exhaust systems shall have the capacity to provide emergency purge of escaping refrigerant at a rate of 30 air changes per hour (ACH) for ammonia, or for other refrigerants as determined in accordance with Equation 1107.2: Where:

Q	=	Air flow rate, cubic feet per minute.
G	=	Refrigerant mass in largest system, pounds.

For SI units: 1 cubic foot per minute = 0.00047 m³/s, 1 pound = 0.453 kg

Where a refrigerating system is located outdoors more than 20 feet (6096 mm) from buildings opening and is enclosed by a penthouse, lean-to, or other open structure, natural or mechanical ventilation shall be provided. The requirements for such natural ventilation shall be in accordance with the following:

1. The free-aperture cross section for the ventilation of a machinery room shall be not less than as determined in accordance with Equation 1107.3.
   (Equation 1107.3)
   Where:

   F	=	The free opening area, square feet.
   G	=	The mass of refrigerant in the largest system, any part of which is located in the machinery room, pounds.

   
   For SI units: 1 cubic foot per minute = 0.00047 m³/s, 1 pound = 0.453 kg
2. The location of the gravity ventilation openings shall be based on the relative density of the refrigerant to air. [ASHRAE 15:5.11.5(a), (b)]

Exhaust inlets or permanent openings shall be located to provide ventilation throughout the entire refrigeration machinery room.

Fans providing refrigeration machinery room refrigerant exhaust in accordance with Section 1107.2 shall be permitted to be automatically or manually controlled to provide intermittent ventilation where the machinery room is occupied or in accordance with Section 1107.10.

Fans required by Section 1107.2 to provide emergency purge ventilation shall be activated by refrigerant Alarm 1 in accordance with Section 1106.4 and by a clearly identified switch of the break-glass type, or protected by an approved tamper resistant cover located immediately adjacent to and outside of the principal refrigerant machinery room entrance. Two colored and labeled indicator lamps responding to the differential pressure across the purge fan or current through the fan motor shall be provided for each switch. One lamp shall indicate flow; the other shall indicate no flow.

Exhaust from mechanical ventilation systems shall comply with Section 502.2.2.

Fans and associated equipment intended to operate the emergency purge of other than Group A1 or Group B1 refrigerants shall be in accordance with the requirements for a Class I, Division 1 hazardous location as specified in the electrical code.

Makeup air intakes to replace the exhaust air shall be provided to the refrigeration machinery room directly from outside the building. Intakes shall be located as required by other sections of the code and fitted with backdraft dampers or other approved flow-control means to prevent reverse flow. Distribution of makeup air shall be arranged to provide thorough mixing within the refrigeration machinery room to prevent short circuiting of the makeup air directly to the exhaust.

Ventilation or mechanical cooling systems shall be provided to maintain a temperature of not more than 104°F (40°C) in the refrigerant machinery room under design load and weather conditions.

Joints and refrigerant-containing parts of a refrigerating system located in an air duct carrying conditioned air to and from an occupied space shall be constructed to withstand a temperature of 700°F (371°C) without leakage into the airstream. [ASHRAE 15:8.8]