HVAC

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HVAC

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GSA Building PerformanceandCustomer SatisfactionWorkshop : 

GSA Building PerformanceandCustomer SatisfactionWorkshop HVAC System Selection and Design PBS P100 Chapter 5 Mechanical Engineering HVAC Requirements Summary

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC General Requirements Design for current uses, plan for future uses Design for maintainability and reliability Design for sufficient redundancy (not “stand-by”) Design state-of-the-art, not experimental Coordinated and integrated with other building systems Responsive to local climate Design for controllability Consideration of local code requirements (site specific) Selection based on lowest Life Cycle Cost

HVAC System Selection and Design : 

HVAC System Selection and Design Energy Analysis and Life Cycle Costing Computer simulations of annual energy consumption (DOE2) Baseline system + 2 alternatives Computer simulations of life cycle costs (BLCC) 25 year life cycle Specific hours of operation Decision making tool Use in schematics or design development

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Baseline System Dual-fuel boilers Electric, water-cooled chillers Cooling towers with multi-speed condenser fans Primary/secondary piping (reverse return) Variable speed pumping Black steel or copper piping Non-permeable piping insulation Perimeter convectors for envelope heat losses

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Baseline System Simple Variable Air Volume (VAV) air handlers 25,000 cfm maximum size Cooling only Variable speed drives UVC emitters for microbial control Air-side, dry bulb economizer Low leakage ductwork Ductwork externally insulated Direct Digital Controls (DDC) Building Automation System (BAS)

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Zoning Criteria Interior zones vs. perimeter zones Corner offices are dedicated zones Dedicated air handlers for courtrooms 2 courtrooms max on any air handler

HVAC System Selection and Design : 

HVAC System Selection and Design Arrangement of Mechanical Spaces Floor-by-floor air handlers ~2% of floor’s gsf for ahu room Central heating and cooling plant Location is building specific ~3% of typical floor’s gsf Heat rejection equipment (e.g. cooling towers) Location is building specific ~1.5% of typical floor’s gsf Appropriate circulation and equipment access allowances

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Heating Systems Heating source Low temperature, hot water boilers preferred District steam allowable if LCC feasible Electric resistance/electric boilers prohibited Northern climates 3 equally sized boilers (combined for 120% peak capacity) Southern climates 2 equally sized boilers (each at 67% peak capacity)

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Cooling Systems Cooling source High efficiency electric, gas or steam chillers District chilled water allowable if LCC feasible Due consideration of part-load performance If peak cooling load is 500 tons+ 3 equally sized chillers (combined for 120% peak capacity) If peak cooling load is less than 500 tons 2 equally sized chillers (each at 67% peak capacity) No CFC refrigerants allowed Cooling tower cells to match number of chillers

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Air Distribution Systems High performance VAV air handlers Maximum 25,000 cfm per unit High efficiency filters (30% pre and 85%final) Air side economizer for free cooling Humidification only as required Consideration of performance of VAV boxes and diffusers Consideration of sound performance at peak capacity Raised floor supply plenum Properly seal to minimize leakage Include anti-microbial coating

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Pumping and Piping Systems Primary/secondary pumping arrangement Variable flow pumping on secondary Isolation of piping at all main equipment Non-permeable piping insulation

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Control Systems Direct Digital Controls (DDC) Minimize simultaneous heating and cooling Night set-back and set-up to end each day Morning warm-up or cool-down to start each day Air and water temperature reset controls Building Automation System (BAS) LCC justified “Open” communication protocol (BACnet, LonMark) Integration of HVAC controls, lighting controls Integration of instrumentation for energy measurement

HVAC System Selection and Design : 

HVAC System Selection and Design HVAC Submission Requirements Conceptual/Schematic Design Narrative description Plans showing HVAC equipment spaces Design Development Narrative description Load, energy and LCC calculations Plans showing major duct runs, system flow diagrams Construction Documents Narrative description Final calculations Final HVAC plans and diagrams Specifications