Special Walk-In Weather Proof Specs

Pritchard Brown Weather Proof Equipment Enclosure Specification No. 2150

(Replaces P-B Specification No. 9940)

Design Criteria:


Weather Proof walk-in style enclosure (See Definitions Below).

Rated to a wind load of 120mph (Higher loading on request)
Roof load equal to 40 lbs/ft2 (Higher loading on request)
Distributed floor load to 200 lbs/ft2 (Higher loading on request)
Rain test equal to 4 inches/hr.
Basic structure meets all seismic requirements of Zone 4 or equivalent.


The enclosure will consist of a roof, two sidewalls, two end walls, and an optional floor/underframe incorporating prepainted aluminum stressed-skin semi-monocoque construction.


The roof shall incorporate a positive camber and be comprised of a mill-finish 6063-T6 extruded aluminum perimeter channel or “roof rail” with 16 gauge (minimum) roll-formed galvanized crossmembers or “roof bows” mechanically fastened to the roof rails. In a drop-over (no floor/underframe/tank) enclosure, two (2) roof lift rings per side (4 total) of 10,000 pound capacity each shall be located within the roofrail perimeter for the purpose of handling the enclosure. Integral structural “spreader bars” shall be incorporated between adjacent pairs of lift rings.

The roof skin shall be a nominal 0.040-inch thick 3003-H16 or 3105-H14 mill-finish aluminum sheet and fastened to the roof bows and roof rails. The top skin shall be rolled over the perimeter of the roof rails to provide additional weather protection. A weatherproof mastic/sealant shall be used at the perimeter, as well as any joints required in the roof skin. The top skin shall be comprised of separate sheets of roof skin joined with lock-seam construction. This joint(s) shall include a high performance mastic tape or sealant for both joint structural integrity and weather protection.


The walls shall be manufactured utilizing mill-prepainted 0.040 inch thick (nominal) 3004-H36 aluminum panels hard-riveted 3 inches on center to 3-inch fabricated aluminized steel “Z” section wall posts located on 24 inch (maximum) centers. The enclosure walls shall incorporate an extruded structural “panel-cap” of mill finish extruded 6063-T6 aluminum.

The panel-cap will interlock into the adjoining roofrail for a weatherproof structural connection between the roof and sidewalls. The bottom exterior of the sidewalls will incorporate a mill finish extruded 6063-T6 aluminum “rubrail” for a structural connection of the sidewalls to the base perimeter or enclosure tie-down frame (drop-over enclosure, only).

Corner Posts:

Corner posts shall be pairs of mating/interlocking mill finish 6063-T6 aluminum extrusions with one-half of each pair attached to the end of the wall. The halves will interlock upon assembly forming a structural, weatherproof corner.

Removable End Walls (optional):

End walls shall be of a removable type retained with 0.250-inch stainless steel thread-forming hardware to facilitate equipment installation and maintenance. Available on all enclosure end walls without adjacent intake/exhaust plenums.

Floor/Underframe (if applicable):

The floor structure shall be rated for a minimum distributed load of 200 lbs./ft2 and reinforced as required to support prevailing point-loading. The floor and underframe assembly shall consist of rectangular steel tubing or structural I-beams welded to form the outer perimeter. This perimeter shall be combined with formed or structural steel crossmembers (nominal 16-inch centers) so as to create a welded steel support structure. Steel tapping angles (nominal 0.375-inch thick) shall be incorporated into the floor structure for adequate structural support and attachment of the generator set and vibration isolators. The crossmembers shall be overlaid with a composite of 0.72-inch thick (nominal) oriented strand board (OSB) covered by a commercial quality, heavy duty vinyl tile or sheet material.


Commercial doors shall be of 18-gauge Galvanized steel construction painted to match the enclosure exterior and incorporated into 16-gauge painted Galvanized steel frames that are structurally integrated into the enclosure wall. The door(s) shall include heavy-duty continuous aluminum gear hinges and a passage latch, which includes commercial key-sets. The passage latch shall incorporate a handicapped-access style lever-type operator for ease of egress in the event of emergency. The latch hardware shall allow escape from within when locked externally. Doors shall include a positive restraint to prevent the door from opening more than 100 degrees in normal operation. Door holdback hardware shall be provided to secure the door to the enclosure wall when the door is opened approximately 180 degrees during installation and maintenance evaluations. Wall adjacent to door includes aluminum protector plate for impact protection from the protruding door handle. All door openings shall include an overhead rain gutter for channeling rainwater away from the enclosure. Panic bar exit hardware will be available upon request.

Lift Points:

Lift rings shall be provided at the base perimeter for the purpose of lifting the complete enclosure with installed equipment into place. The lift rings shall be 1.25-inch (nominal) steel plate and welded into the base or rupture basin (if applicable) perimeter at 4 locations.

Available Options (specify when required):

  • Higher wind, wall, floor, and roof loading
  • Interior Lining:
    • Perforated mill finish aluminum
    • Stucco-embossed white or mill finish aluminum
    • Smooth prepainted aluminum
    • Wood panelingFRP sheet
    • Plywood
    • Carpet
    • Others on request
  • Floor covering: Steel sheet or plate, coated with non-skid material
    Diamond plate steel
  • Carpet
  • NEC/NFPA Electrical Package
  • “Panic-bar” door hardware
  • Mechanical installation of customer-furnished equipment
  • Electrical installation of customer-furnished equipment
  • Fire detection and suppression systems
  • Gas detection systems
  • “Solar Shade” roof for high temperature environments
  • Icicle/hail resistant roof
  • Enclosure removable from base
  • Removable access panels
  • HVAC packages
  • EMI/RFI shielding
  • Ballistic protection
  • Environmentally sealed systems


Weather Proof– Allows moisture or the elements into the enclosure in amounts less than that, which will ultimately contact “live” electrical equipment.

Weather Resistant or Drip-proof– Allows moisture or the elements into the enclosure in amounts less than that, which will cause installed equipment to malfunction or fail. (See Specification No. 2110 and 2130)

Sound Attenuated– Reduces source noise by a minimum of 3 dB(A). Levels of reduction through 40dB (A) are routinely specified depending on site conditions and prevailing local codes. (See Specification No. 2120 or 2130)

Louver– A fixed or moveable b lade device used generally for inlet air handling where the blades, when fully open, are at an angle opposed to inlet airflow. Louvers are generally not used in an air discharge application due to their restrictive qualities. The movable blade or operable louver is either manually operated or motorized with associated controls. Louver blades may be of fabricated or extruded design, with extruded blades of the drainable type offering superior weather protection.

Dampers– Operable blade air handling devices generally used in a radiator or fan discharge opening. They may be used within an inlet air opening otherwise protected by an inlet air-handling device such as a louver, inlet hood or acoustigrid for the purpose of controlling the internal enclosure environment when the genset is not operating. Since their blades, when fully open, are at 90 degrees and offer no weather protection, dampers should never be used as primary inlet air handling devices. Inlet dampers are generally motor operated, while exhaust dampers may be gravity or motor operated.

Hood– An inlet or discharge air handling device typically covering an inlet or discharge opening and used for weather protection and/or sound attenuation.

Acoustigrid– A sound attenuating inlet or discharge air handling device comprised of acoustical materials arranged in a matrix or grid. When used as an inlet device, it is set within the enclosure wall at an angle so as to minimize the entrance of weather and be self-draining.