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Basis of Design
This ction applies to the design and installation of ductwork, air terminal boxes, air outlets and inlets, volume dampers, pressure relief dampers, smoke/fire dampers, and smoke/fire damper actuators.
Design Criteria
成人高考分数查询•Select duct velocities to meet N.C. requirements of each occupied space. NC level requirements shall be identified in the Basis of Design narrative. Coordinate required NC
levels with University Project Manger and urs.
Supply, Return and Non Fume Exhaust Ductwork
•Provide a 6-inch pressure rating for supply ductwork and plenums between the supply fan and the zone terminal boxes; for ductwork downstream of the terminal box, provide a 2-inch
pressure rating. If pressure class less than tho given above are considered sufficient for
a specific application, review with Campus Engineering before specifying a lower rating.
•For return and exhaust ductwork and plenums, lect a rating that will avoid damage to ductwork in event of sudden smoke/fire damper closure during fan operation.
•U the ASHRAE Handbook of Fundamentals chapter on duct design to determine the allowable leakage rate (cfm/100 sq.ft.) at the specified test pressure for each type of
ductwork on the project other than fume exhaust ductwork. Specify for each type of ductwork
the duct pressure rating, the pressure to apply during the duct leakage test, and the allowable
我喜欢春节cfm/100 sq.ft. leakage rate at the test pressure.
•Minimize u of square elbows. Provide turning vanes in square elbows of supply ductwork.
Do not u turning vanes in return or exhaust ductwork.
•To minimize noi levels in the space, avoid substitution of registers for balancing dampers.
•Provide a balancing damper for each outlet and each inlet. Locate tho balancing dampers adjacent to the connection to the main branch to minimize noi levels in the space.
•Do not u perforated plate ceiling diffurs without approval from Campus Engineering.
They cau dumping.
•Do not u nonmetal ductwork (i.e. fiberboard) without the approval of Campus Engineering.
•Design ductwork to and from the HVAC equipment carefully so that stratified air will be mixed properly before entering branch ducts or downstream equipment.
•Limit flexible duct to no more than 6 feet and one elbow.
•On renovation and remodel projects, obtain the latest existing supply and exhaust air quantities and incorporate into the design.
Dampers
•Install manually operated, oppod blade or single blade, quadrant-type volume dampers on all branch main and branch duct takeoffs from the main duct to control the amount of air
entering or leaving the branch.
•Avoid register or diffur-mounted dampers becau they cannot reduce large volumes of air without causing objectionable air noi levels.
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•Do not locate single blade volume dampers immediately behind diffurs and grilles. This application does not allow uniform airflow across the outlet face.
•To minimize generated duct noi, locate volume dampers at least two duct diameters from a fitting and as far away as possible from the outlet or inlet.
•Provide the necessary access space around components to allow the TAB technician to take proper readings. Allow adequate straight duct ctions from fan outlets, elbows, or open duct ends to provide accurate duct traver readings.
Pressure Relief Doors or Panels
•Smoke/fire dampers have the potential to damage ductwork if they clo by accident, or even if they clo when the fan is shut off but wheeling down during a power outage, fire test, or
fire. Risk of damage to the ductwork is particularly rious if a single smoke/fire damper will arrest the full supply of air into or out of a large fan. Design the air distribution system so that the ducts wo
n’t be damaged if the fans are run with the smoke fire dampers clod.
•The preferred means for protecting the ductwork against over-pressurization during smoke/fire damper closure is to lect a duct pressure classification so the ducts will
withstand sudden exposure to the maximum fan pressure. Provide accessible, well-aled
pressure relief doors or panels that can be clod after they open.
•U pressure relief doors rather than pressure relief backdraft dampers.
Mounting
•For exterior ductwork, fans and air handlers, e the Facilities Services Design Guide architectural standard drawing titled Mechanical Equipment Mounting, for minimum mounting height. Coordinate with Architect to specify rooftop mounting under Architectural.
Renovation and Expansion Projects
•When adding or removing ductwork on an existing air distribution system, show on the mechanical drawings all existing ductwork and flow rates that will need to be rebalanced after construction.
•Review manufacturer’s fan data for existing fans to ensure the fans can operate at the new operating conditions. Review existing motor amperage and motor nameplate to determine
whether a new fan motor should be specified.
•In the fan schedules, provide the existing and propod fan airflows, fan static pressures, motor amperages and motor horpower requirements for existing fans rving systems
altered in renovation projects. The existing actual flows are needed for the design. Arrange with the University of Washington Project Manager for flow measurements as needed.
•On floor plans, show any new balancing dampers that should be added to the existing branch ductwork to facilitate balancing.
•Require measurements, prior to demolition, of any unknown airflows or static pressures that will need to be reestablished as part of testing, adjusting and balancing.
•If a small portion of an existing system is to be changed, avoid creating a new high pressure drop critical path to an existing system. Larger components should be lected to avoid
significant increas in the fan discharge pressure requirements.
•Provide temporary means as necessary for dust control and lab safety while ductwork and fans are being removed and installed.
Fan-powered Zone Air Terminal Boxes
•For VAV air terminal box fans, specify the method of speed adjustment (e.g., continuous or 3-speed fan control) to be ud during testing, adjusting and balancing. In reviewing
manufacturer’s literature during design and during contractor equipment submittals, make
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sure the lected air terminal boxes will operate at a speed range that doesn’t create excess noi or motor problems. Specify “extra-quiet” fan-powered VAV boxes.
•Specify maximum sound ratings (db level) for the air terminal boxes.
•To control sound transmission out of the condary (plenum) air intake, include a lined intake boot that has at least one 90 degree elbow.
•On mechanical floor plans, indicate with dotted lines the horizontal access clearance requirements for maintenance of air terminal boxes.
•Connect fan powered air terminal boxes to the ductwork with flex connections.
•Connect air terminal boxes to structure with vibration isolators.
Smoke/Fire Dampers
•The smoke/fire dampers and their actuators are to be covered under the ductwork specialties ction of the project specifications (not under controls or the fire alarm system). Exception: The EP switch for smoke/fire damper pneumatic actuators will be specified under the fire
alarm system. Coordinate with electrical and refer to Environmental Health & Safety Design Guide – Fire Alarm System ction.
•The University strongly discourages u of engineered smoke control systems. Consult EH&S before designing one.
•Work with the Architect and EH&S to minimize the number of smoke/fire dampers through (1) coordination of duct layout with suite configuration, and (2) clo attention to code
“exceptions” to standard smoke/fire damper placement requirements.
•U pneumatic actuators. Electric smoke/fire dampers shall only be ud in retrofit projects where electric smoke/fire dampers are already installed.
•If electric smoke/fire dampers are to be ud, discuss actuator application including noi with Campus Engineering.
•Dampers shall be Class II, 250° F, with a minimum closure time of 7 conds and a maximum closure time of 15 conds.
•Fire damper actuating device shall be approximately 50° F above normal operating temperature within duct system. Rate for 286° F for smoke control systems.
•Do not u fire dampers in laboratory hood exhaust systems.
•Provide end switch for position verification.
Access Doors and Panels
•Coordinate with Architect to ensure there are access doors through walls and hard ceilings wherever necessary to reach access doors in the HVAC equipment.
•Access doors and panels should be a minimum of 24" x 24" unless the duct is too small to accommodate a larger door or the necessary access can be handled easily with a smaller
door.
•Coordinate with Architect so that all access doors and panels in the ductwork are accessible in a manner that meets applicable safety standards. This includes access doors and panels
located at the smoke/fire dampers.
Hospitals, Labs, and Animal Holding Facilities Pressure Relationships
•On hospital, lab, and animal holding facilities projects, discuss with EH&S and Campus Engineering whether there are any special requirements for documentation and review of
room pressure relationships.
•See EH&S Laboratory Safety Design Guide.
Design Evaluation
The following information is required to evaluate the design:
•Programming Pha: On retrofit projects, descriptions of existing systems to be altered. For all projects, provide design criteria for ventilation, heating and cooling and noi levels. Basic
strategy for zoning air distribution system.
•Schematic Design Pha: Identify all systems; include single line system flow diagrams, outside air and exhaust outlet locations, shaft locations, and design calculations.
•Design Development Pha: Provide single line duct layouts, outside air intake calculations, updated single line flow diagrams, equipment schedules, design calculations, and outline
specifications.
•Construction Document Pha: Provide fan curves that demonstrate the duct rating is high enough to withstand the deadhead fan pressure for the basis-of-design fan lections.
Provide double line duct layouts, final single line system flow diagrams (Supply air, return air,
and exhaust air), equipment schedules, design calculations, and final specifications. Construction Submittals
•For smoke/fire damper submittals: Include the number of damper actuators in each damper bank, and an equipment list showing the manufacturer, model number, and amperage draw
for the actuators in each damper bank (whether compod of a single or multiple dampers).
•Include manufacturer’s literature on the smoke/fire damper actuators.
•For projects with electric smoke/fire dampers, provide shop drawings that show electrical and mechanical coordination of smoke/fire dampers.
Related Sections白色英文
•Facilities Services Design Guide – Mechanical - General Requirements
•Facilities Services Design Guide – Mechanical - Heating, Ventilating and Air Conditioning o Air Handlers and Ventilation Fans
o Filters
o Coils
o HVAC and HVAC Piping Pressure Testing
o Facilities Services Design Guide – Mechanical - Hangers and Supports
o Facilities Services Design Guide – Mechanical - Metering and Gauges
o Facilities Services Design Guide – Mechanical - Nonstructural Component Seismic Design
o Facilities Services Design Guide – Mechanical - Identification
o Facilities Services Design Guide – Mechanical - Insulation
o Facilities Services Design Guide – Mechanical - Noi and Vibration Control
o Facilities Services Design Guide – Mechanical - Testing, Adjusting and Balancing
o Facilities Services Design Guide – Mechanical - Commissioning
Products, Material and Equipment
Accessories
•Provide insulated drip pans for cooling coils.中药止咳
Ductwork – Non Fume Exhaust
•Provide an easily accessible lockable, handle for each balancing damper. Orient the handle parallel to the damper blade(s).
•U aluminum sheet metal with watertight joints for exhaust ductwork from high humidity areas such as shower rooms. Slope ductwork back toward inlet.
Fan-powered Zone Air Terminal Boxes
•Internally isolate the fans in air terminal boxes.
•Line the air terminal boxes with at least 1 inch of fiberglass batt insulation. Cover liner with aluminum foil at least 0.001 inch thick to prevent entrainment of fibers into the air stream.
•Damper shafts shall have at least one flat facet at the point of connection to the actuator.
Damper Shafts
•Provide a grooved scribe running parallel to the blades on the end of each damper shaft, including but not limited to shafts on balancing, and smoke/fire dampers.
Fume Exhaust Ducting什么百年树人
•Provide ducts that are round, non-combustible, inert to agents to be ud, non-absorbent, and free of any organic impregnation.
•Provide liquid and airtight joints.
•Provide smooth, non-porous lining surfaces free of cracks, joints, or ledges.
•U flexible connection ctions of ductwork, such as hypalon or neoprene-coated glass fiber cloth, between the fan and its intake duct when such material is compatible with hood
chemical u factors. Provide the transition joint from duct to fan of a amless, constant
diameter, inert, corrosion and ultraviolet-resistant material as approved by Owner. Provide
the duct alignment within ½ inch at the hood collar and fan.
