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Provisions shall be made for make-up air to replace the air that is being exhausted. Openings for make-up air shall be located to avoid intake of exhaust air. Supply and exhaust ducts to the machinery room shall serve no other area, shall be constructed in accordance with Article 5 and shall be covered with corrosion-resistant screen of not less than 1/4-inch (6.4 mm) mesh.
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 20cfm (0.009 m
3
/s) per person; or
2. A volume required to limit the room temperature rise to 18°F (10°C) taking into account the ambient heating effect of all machinery in the room.
Upon actuation of the refrigerant detector required in Section 18-28-1105.5, the mechanical ventilation system shall exhaust air from the machinery room in the following quantity:
where:
Q = The airflow in cubic feet per minute (m3/s).
G = The design mass of refrigerant in pounds (kg) in the largest system, any part of which is located in the machinery room.
Pressure-relief devices, and purge systems located within the machinery room shall terminate outside of the structure at a location 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.
Pressure-relief valves for ammonia systems shall discharge in accordance with ASHRAE 15. Piping from Ammonia Refrigerant (Group B2) shall terminate above the roof of the highest story of the building and shall be at least 40 feet (12.192m) from any adjoining building which extends above the roof and at least 40 feet (12.192m) from any penthouse, skylight, fixed ladder or exhaust duct system. Piping shall terminate downward at an angle of 45 degrees from the horizontal, and shall be provided with a permanent warning sign attached to the piping at the point of termination. The sign shall have a yellow background and shall state in black letters not less than 3 inches (76.2 mm) in height in both Spanish and English.
AMMONIA VENT - DANGER AMONIACO DESCARGA - PELIGRO |
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