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HVAC design guide for large owner maintained multi-wing facility 5.1 Introducti

HVAC design guide for large owner maintained multi-wing facility 5.1 Introduction A. The primary objective of these standards is to achieve consistency in the mechanical design. These guidelines are general and are supplemented by the applicable codes, standards, and guides referenced in this manual. B. As a minimum, all new and renovated construction will conform to the 2009 International Mechanical Code (IMC) and the 2009 International Plumbing Code (IPC). C. Additional standards listed in Appendix Section of this report can be referenced if appropriate for a specific project. This will have to be determined by designer on a project by project basis. D. A design narrative with specific project criteria is to be developed so that project design requirements can be available in a written format to all reviewing parties. Commercial specifications along with detailed design drawings are required to be incorporated in all final construction bid packages. Final mechanical as-builts will be produced during the construction phase. E. New construction energy consumption shall be at least 30% less than ASHRAE 90.1 2007 standards. Renovation project energy consumption shall be at least 20% less than ASHRAE 90.1 2007 standards. F. Endeavor to reduce energy consumption by 50% below ASHRAE 90.1 2007 standards if Life Cycle Cost justified. 5.5 Mechanical Equipment Selection – General A. All energy consuming equipment shall be selected on minimum capacity, physical size, configuration, special features AND the lowest Life Cycle Costs B. A description of equipment is required to be indicated on the equipment list drawings. The engineer is required to locate and describe one manufacture’s model that meets design requirements. The following guidelines are required: 1. Indicate the manufacturer’s catalog number and performance information. 2. Provide additional specifications to describe complicated equipment. 3. Use performance data that will ensure a quality product and the lowest Life Cycle Cost. 4. Key mechanical items numbers to the plans and details. 5. Manufacturer’s actual performance data is required for capacity equipment. 6. All equipment assemblies requiring line electrical power will have a local disconnect provided by electrical contractor or manufacturer. Coordinate with electrical engineer exact requirements per each piece of equipment. 5.6 VENTILATION:  Ventilation systems shall include a 100% outside air capacity economizer.  Variable volume, temperature and pressure ventilation systems are typically required using pressure independent VAV boxes.  Constant volume applications will incorporate pressure independent VAV boxes.  Pressure independent VAV boxes will be used on exhaust side for spaces requiring pressure control.  Full time 100% outside air systems will require a minimum 50% heat recovery package. FANS & Air Handling Units (AHU):  Fans will be selected and sized to minimize noise in order to minimize the need for sound attenuation.  In fan systems totaling 10 HP or more, capacity will be adjusted using Variable Frequency Drives (VFD). Use OWNER standard VFD specifications and instructions.  Fan motors 1 HP and larger will be premium efficiency 1800 RPM unless a different speed is approved by OWNER. Size motors so that they operate at about 80% load at maximum anticipated airflow.  If fan HP requirement is ≥10 HP for any single purpose, use multiple direct drive plug fans in a wall type configuration (Huntair, Trane, Aaon or approved equal) rather than one large fan.  Packaged Roof Top AHUs will have a minimum R-13 insulation value.  Note: Aaon manufactures AHUs and packaged units with variable speed compressors, variable speed multiple fan walls and minimum R-13 insulation. All at a similar price to competitors with conventional features. AIR FILTERS:  Owner has studied air filters and determined the lowest LCC product for each application. An approved equal would produce an equal or lower LCC to the specified filters.  Size filter banks so that only 2’x 2’ and 1’x 2’ filters are used and air velocities should be no greater than 4500 FPM.  Use 4” deep MERV 8 high capacity filters in typical applications.  Use 22” deep MERV 13 bag filters if needed to acquire LEED points.  Areas requiring higher efficiency air filters shall use 4” deep MERV 8 high capacity prefilters and 22” deep MERV 15 final filters. It is also acceptable to use 12” deep rigid filters that provides the lowest total cost of ownership as determined by the BetterBricks Air Filter Comparison Calculator. http://www.betterbricks.com/DetailPage.aspx?ID=943 HEAT EXCHANGE COILS:  Heat exchange coils should be designed for 14 degree F cooling and 20 degree F heating temperature differentials. DUCTWORK  Do not use more than 4 feet of flexible ductwork unless it is necessary in retrofit applications.  Do not expose fiberglass to the ventilation system air stream or to occupied space.  Use full radius or splitter vane elbows only.  Select duct velocities to meet N.C. requirements of each occupied space.  Do not use opposed blade damper registers in occupied spaces. Locate balancing dampers next to the connection to the main branch or terminal box to minimize noise levels in occupied spaces. Insure that these dampers are accessible.  For return and exhaust ductwork, select a pressure rating that will avoid damage to ductwork in event of sudden smoke/fire damper closure during fan operation.  Protect ductwork from overpressure due to the sudden closing of dampers. Provide accessible, well-sealed pressure relief doors or panels that can be closed and sealed with out special tools or new parts after they blow open. DAMPERS:  Construct damper blades of minimum 14 gauge galvanized steel and damper frames of minimum 16 gauge galvanized steel. Provide opposed blade action with stainless steel compressible jamb seals and extruded blade edge seals suitable for 0 degrees F to 250 degrees F. Blades shall rotate on stainless steel sleeve bearings. Damper blade lengths shall not exceed 60 inches. Leakage rate shall not exceed 5 CFM/square foot at 1-inch water gage and 9 CFM/square foot at 4 inches water gage. Leakage and pressure ratings shall be based on AMCA Publication 500.  Damper shafts shall have at least one flat facet at the point of connection to the actuator.  Provide a grooved scribe running parallel to the blades on the end of each damper shaft.  Outside, Return and Relief air dampers shall be independently driven and controlled.  Large damper assemblies shall be made of individually driven sections that are small enough to ensure reliable operation and uniform closure across the entire damper assembly when operated by a single actuator. HVAC ACTUATORS:  Generally, actuators shall use 24 VAC power, analog control (or floating point control with position feedback) and mount around a rotating shaft to modulate dampers and valves.  Provide actuators with at least 150% of the required device torque.  Damper actuators shall be operated and controlled independently so that if one damper segment or actuator becomes inoperable, the others remain operable.  When adequate control air is available, use pneumatic actuators for large valves. Two stacked electric actuators may be used with OWNER approval for large valves.  Mount electric actuators horizontally to hot water valves. ACTUATED VALVES:  Modulating 2-way control valves shall be pressure independent.  3-way valves shall not typically be used. A 2-way controlled bypass may be used to maintain a minimum water flow.  Pressure independent flow control valves will not generally need circuit setters or dedicated strainers.  Two-position valves shall be of a rotating type and may be ball, shoe or butterfly depending on size and application.  Valves 2.5” and smaller shall be stainless steel, brass or bronze.  Valve stems shall have at least one flat facet at the point of connection to the actuator. CHILLERS:  In general, variable speed chilled water systems will be used for cooling applications.  Lowest total cost of chiller ownership will be the primary criteria for purchase so anticipated energy consumption will be used in conjunction with the installed cost and anticipated O&M costs to determine the “best bid”.  Typically, variable speed compressors will produce the lowest total cost of ownership.  OWNER will provide a chiller selection tool characterized for the specific needs of the project. The mechanical designer will assist in creating a load profile for this tool.  Air Cooled chillers <200 tons will be considered if LCC justified.  Hybrid systems using indirect evaporative cooling, direct evaporative cooling and/or refrigerated cooling may be considered to reduce life cycle costs (LCC).  Small DX units may be allowed for small process loads such as data centers or labs.  If practical, cooling equipment should be provided in sizes and configurations so that hot gas bypass is never needed.  Reciprocating compressors are not allowed. PUMPS:  Generally, variable speed pumps will be selected for N+1 operation such that all but one pump can operate at 60 HZ and produce 100% design flow. For example, three chilled water pumps might be installed and sized so that two pumps must run at 100% speed in order to maintain design flow. Typically all three pumps will operate in parallel at uploads/Geographie/ hvac-design-guide.pdf