5.7 Arrangement of Mechanical Spaces
Minimum Space Requirements. A minimum of 4 percent of the typical floor’s gross floor area shall be provided on each floor for air-handling equipment. A minimum of 1 percent of the building’s gross area shall be provided for the central heating and cooling plant (location to be agreed upon during preparation of concept submission. Space requirements of mechanical and electrical equipment rooms shall be based upon the layout of required equipment drawn to scale within each room.
Service Access. Space shall be provided around all HVAC system equipment as recommended by the manufacturer and in compliance with local code requirements for routine maintenance. Access doors or panels should be provided in ventilation equipment, ductwork and plenums as required for in-site inspection and cleaning. Equipment access doors or panels should be readily operable and sized to allow full access. Large central equipment shall be situated to facilitate its replacement. The HVAC design engineer should be cognizant of the necessity to provide for the replacement of major equipment over the life of the building and should insure that provisions are made to remove and replace, without damage to the structure, the largest and heaviest component that cannot be further broken down.
In addition, adequate methods of access shall be included for items such as: chillers, boilers, heat exchangers, cooling towers, reheat coils, VAV boxes, pumps, hot water heaters and all devices that have maintenance service requirements.
Vertical Clearances. Main mechanical equipment rooms generally shall have clear ceiling heights of not less than 3.6 m (12 feet). Catwalks shall be provided for all equipment that cannot be maintained from floor level.Where maintenance requires the lifting of heavy parts [45 kg (100 pounds) or more], hoists and hatchways shall be installed.
Horizontal Clearances. Mechanical rooms shall be configured with clear circulation aisles and adequate access to all equipment. The arrangement shall consider the future removal and replacement of all equipment. The mechanical rooms shall have adequate doorways or areaways and staging areas to permit the replacement and removal of equipment without the need to demolish walls or relocate other equipment. Sufficient space areas (noted by outlining manufacturer’s recommendations) for maintenance and removal of coils, filters, motors, and similar devices shall be provided. Chillers shall be placed to permit pulling of tubes from all units. The clearance shall equal the length of the tubes plus 600 mm (2 feet). Air-handling units require a minimum clearance of 750 mm (2 feet 6 inches) on all sides, except the side where filters and coils are accessed. The clearance on that side should equal the length of the coils plus 600 mm (2 feet).
Roof-Mounted Equipment. No mechanical equipment except for cooling towers, air-cooled chillers, evaporative condensers, and exhaust fans shall be permitted on the roof of the building. Access to roof-mounted equipment shall be by stairs, not by ship’s ladders.
Housekeeping Pads. Housekeeping pads shall be at least 150 mm (6 inches) wider on all sides than the equipment they support and shall be 150 mm (6 inches) thick.
Mechanical equipment rooms must be designed in accordance with the requirements of ASHRAE Standard 15: Safety Code for Mechanical Refrigeration.