Appeal 34909

NFPA 110, Sections 7.7.2.1 and 7.7.4.2

7.7.2.1: “For EPS supplying Level 1 EPSS, ventilation air shall be supplied directly from a source outside the building by an exterior wall opening or from a source outside the building by a 2-hour fire-rated air transfer system.”

7.7.4.2: “Radiator air discharge shall be ducted outdoors or to an exterior opening by a 2-hour rated air transfer system.”

Due to the unique site conditions and existing generator installation location, there are no available locations on the building façade for generator air intake or exhaust louvers. This appeal proposes:

1. To supply combustion and cooling airflow to the emergency generator from the parking garage.
2. To provide radiator air discharge through a louver directed into the parking garage.

The existing emergency generator is located in a below-grade parking garage. The generator will be enclosed in a 2-hour rated enclosure within the parking garage. A 72”W x 96”H louvered intake opening on one side of the rated enclosure will provide combustion air and ventilation air to the generator. The generator’s radiator will be ducted to a 80”W x 80”H discharge air louver at the opposite end of the rated enclosure. Generator cooling air and combustion air will be supplied to the parking garage through a large screened opening at the garage entry ramp, as well as a louvered intake opening on the main parking level. The existing parking garage exhaust system will be provided with emergency power and will be interlocked with the generator to continuously exhaust the parking garage during generator operation. Parking garage exhaust is ducted to an existing screened wall opening located at the north building face, approximately 17’ above grade. (See Exhibit B floor plan)

To protect the louvered intake opening and radiator discharge opening at the generator enclosure during the event of a fire, quick-response fire sprinklers will be provided within 12” of the louvered opening on both the interior and exterior of the enclosure, and spaced not less than 6’-0” on center. (See Exhibit B floor plan)
To protect the louvered openings and prevent storage or parking directly in front of the openings, vehicle impact bollards will be provided in front of each louver. (See Exhibit B floor plan)

RECONSIDERATION TEXT:
• The original full floor plans for P1 and P2 have been added, see Exhibit C.
• Mechanical plans showing routing of parking garage ventilation have been added; see Exhibit D.
History: the existing generator was installed in 2022 under Permit No. 2021-028771-ET. The original permit (2021-028771-ET) has recently been reopened and the generator is being permitted under a separate permit from the enclosure. The current design effort includes the addition of a 2-hour fire rated generator enclosure, air intake and exhaust provisions, fuel tank venting, and permitting to bring the existing generator to compliance under a new permit (submittal forthcoming). As part of this effort, this code appeal is being submitted for approval of alternative materials, design and methods in alignment with OSSC Section 104.10 and OMSC Section 105.2.

Current Generator: The existing generator located in the below grade parking garage, and referenced in this appeal, replaced the previous generator located on the roof. The previous rooftop generator was decommissioned. All equipment supported by the rooftop generator was transitioned to the basement generator at the time of installation in 2022 (Permit No. 2021-028771-ET). The basement generator supports the building’s emergency and standby power loads.

The purpose of NFPA 110, Sections 7.7.2.1 and 7.7.4.2 is to ensure that adequate combustion, ventilation and cooling air is provided to the generator to support fuel combustion and to prevent the generator’s environment from exceeding the temperature in which it was designed to operate. The parking garage where this generator is located freely communicates with the outdoors through a large screened opening at the garage entry ramp. An additional louvered intake opening is provided on the main parking level. The existing garage exhaust fan is connected to a duct system that provides complete coverage of both levels of the parking garage. When operating, the garage exhaust fan provides an exhaust rate of 22,000 cubic feet per minute (cfm), which results in a total calculated air exchange of approximately 6.07 air changes per hour. The air within the parking garage is therefore completely exchanged with outdoor air every 10 minutes that the fan is operating. Based on the generator manufacturer’s published data for maximum heat output (319,020 btu/h) and a continuous exhaust rate of 22,000 cfm, the temperature in the parking garage and generator enclosure is anticipated to be no more than 13 degrees (F) above the outdoor ambient temperature during prolonged generator operation. The generator’s cooling system is designed for ambient temperatures up to 122 degrees (F). Based on ASHRAE climatic data for the region and the calculated maximum temperature rise during generator operation, the proposed design will provide adequate cooling air per the generator manufacturer’s requirements and will meet the intent of NFPA 110, Sections 7.7.2.1 and 7.7.4.2.

Reference City of Portland appeals with similar condition: Appeal ID# 32364, 7/3/2024; Appeal ID# 13885, 13519, 6/1/16; Appeal ID#12880, 12/30/15; Appeal ID#12693, 11/12/15; Appeal ID#16416, 11/31/18.

NFPA 110, Section 7.9.12.1

7.9.12.1: “A minimum clearance of 0.9 m (36 in.) shall be maintained on all sides.” [In regards to listed generator subbase secondary containment fuel tanks]

The intent of this appeal is to allow for a reduced clearance from structure on two sides of the subbase fuel tank due to existing conditions.

The existing generator is installed on a UL-listed, 375-gallon subbase secondary containment fuel tank. The fuel tank is located approximately 28 in. from an existing column to the west of the tank. A 2-hour rated enclosure will be constructed around the existing generator, with the west wall aligning with the existing column. To maintain maximum two-way drive aisle clearance in the existing parking garage, the south wall of the enclosure is proposed to be located 25 in. from the fuel tank. A 80”W x 80”H removable louver on the south side of the enclosure will allow for unobstructed tank access. The proposed enclosure will provide 40 in. of clearance on the north side and 46 in. of clearance on the east side of the tank. The generator’s electrical and control panels will have more than 40 in. of clearance to structure, which exceeds the code minimum. The entire generator enclosure will be equipped with a fire suppression system that will provide coverage of all sides of the fuel tank. (See Exhibit B floor plan)

RECONSIDERATION TEXT
The generator referenced as "existing" is currently under a separate active permit: 2021-028771-ET). Requested exhibits have been included with this reconsideration submittal.

The current generator location being 28 in. from the column allows for ample clearance for visual inspection and maintenance. The reduced clearance of 25 in. on the south side will still allow for visual inspection and maintenance, with a removable louver providing unobstructed access for future fuel tank service or replacement. Fuel tank connections and electrical/control panels will all be located on the north and east sides of the tank, with greater than 36 in. of clearance from structure. The generator enclosure will not be used for storage, and will not contain any items that are not necessary for generator operation.