HVAC SYSTEM SCHEMATIC DESIGN

Transcription

1 HVAC SYSTEM SCHEMATIC DESIGN Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 HVAC System Design Process Establish HVAC-related owner s project requirements (OPR: design issues/intents/criteria; including code/standard compliance) Establish zoning requirements Make a preliminary system selection based on the OPR and zoning Calculate preliminary design heating/cooling loads Select appropriate source equipment (to meet loads, OPR, and context) Select appropriate distribution approach (to meet OPR and to fit context) Coordinate HVAC components with other building systems Rough-size equipment (fans, pumps, valves, dampers, pipes, ducts, condensers, airhandlers, tanks, ) Run energy analyses to optimize equipment selections and system assemblies Final-size equipment based upon optimization studies Coordinate final individual equipment selections into a cohesive whole Develop appropriate control logic and strategies Develop commissioning tests and checklists Witness systems installation and verification Develop systems manuals for the owner Provide benchmark performance data for the owner Conduct POE validations of system outcomes in use red = architect blue = engineer with architect black = engineer Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1

2 HVAC System Load Estimations typically done using commercial loads programs Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 Building Energy Use Estimations typically done using one of several simulation programs Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2

3 HVAC System Selection Process Carefully consider potential design issues Clearly define design intents Establish meaningful design criteria Compare potential systems against criteria Select best system Validate system selection collectively, the first three items are the Owner s Project Requirements (OPR) for climate control and IAQ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 5 Common HVAC Selection Issues First cost Life-cycle cost Durability Maintainability Reliability Appearance Zoning capabilities Flexibility Energy efficiency ODP and GWP Greenness Noise Space requirements Smoke control capabilities Fuel options Owner dictates Electrical demand charges Many others Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 3

4 Common HVAC Design Intents Provide thermal comfort Provide acceptable IAQ Low first cost Good energy efficiency No equipment in occupied spaces A green system Highly-reliable operation Easily-maintained equipment Low life-cycle costs And such Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 7 Establish Design Criteria for Each Intent Low first cost means no more than $xx.xx / sq ft Energy efficient means xx% better than the requirements of ASHRAE Standard 90.1 Provide thermal comfort means meets the requirements of ASHRAE Standard 55 ( bettering this standard is not necessarily meaningful; comfort is comfort) Provide good IAQ means meets the requirements of ASHRAE Standard 62.1 ( bettering is expensive to verify and may be energy intensive) Easy to maintain means janitorial staff can do the job No equipment in occupied spaces means as stated Aesthetically pleasing means meets three visual precedents the criteria above are just examples, from a wide world of possibilities Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 8 4

5 Selection Matrix (a design tool) POSSIBLE SYSTEM A POSSIBLE SYSTEM B INTENT PROJECT WEIGHT SCORE SYSTEM A WEIGHTED SCORE SYSTEM A SCORE SYSTEM B WEIGHTED SCORE SYSTEM B Low First Cost Good Energy Efficiency High Flexibility Clean Appearance Good IAQ Capabilities OVERALL RATING * ** * most important attribute/intent; ** second most important; etc. and the most logical system to use in this context is B Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 Common HVAC Coordination Issues Equipment Locations Source equipment (noise, maintenance access, access for replacement, access/connection to utilities) Condenser (must be exterior, noise, appearance, airflow, spray) Air-handlers (length and placement of air supply and return paths, outdoor air access, noise, vibration) Terminal devices (maintenance access, noise, space incursion) Outdoor air intakes (located to provide unpolluted outdoor air) Floor Area for Equipment Main mechanical room(s), satellite AHU/fan room(s), condenser Volume for Distribution (and for Equipment) Ductwork (by itself and in coordination with beams, lighting fixtures, sprinkler piping, electrical and signal runs) Aesthetics Exposed elements (especially diffusers) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5

6 Desired Equipment Locations this is a joint architectural/mechanical decision these 4 examples all work but one will usually make more sense in a given project context a 5 th option (not shown) would be fan room on roof often a spatially-appealing option The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 Required Equipment Locations zone control diffusers are laid out for reasonable air distribution undifferentiated supply air; not yet controlled for specific zones box MUST be in this area zone-differentiated supply air The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 12 6

7 Large Equipment Areas for schematic planning: can estimate central plant room at 7% +/- of conditioned floor area assuming typical systems selections not served by a district system The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 Air Handling Unit Areas USE these simple tools in studio don t just guess The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 7

8 Consider Volume (not just floor area) The Architect s Studio Companion, 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 Volume working in and around structure notice ductwork coordination with concrete beams Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8

9 Volume plenums are never as deep as they seem Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 17 Provide for Access who will know this stuff is up there? Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 18 9

10 Estimating Duct Sizes (another option) For schematic design, assume 1 cfm per square foot for an all-air system (use 0.1 for an air-water system) Duct volume (in ft 2 ) = airflow (in cfm) / air speed (in fpm) cfm = cubic feet per minute (airflow rate) fpm = feet per minute (air speed in ducts) Assume (as a starting point) 1000 fpm air speed higher air speed is possible and fairly common, but it uses more energy and generates more noise (and we re just estimating) Estimate duct dimensions as needed for the area served by a given duct (main ducts, branch ducts, ) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 Estimating Duct Sizes (Examples) For a 200 sq ft office (all-air HVAC) (200 sq ft)(1 cfm/sq ft) = 200 cfm 200 cfm / 1000 fpm = 0.2 sq ft duct size might be around 12 x 3 or 6 x 6 or. and a similar size return air duct may be required For a 3000 sq ft classroom wing (all-air HVAC) (3000 sq ft)(1 cfm/sq ft) = 3000 cfm 3000 cfm / 1000 fpm = 3 sq ft duct size might be 36 x 12 and a similar size return air duct may be required message: ducts can get quite large, and there are often two of them Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 10

11 The Aesthetics of Air Delivery register diffuser diffuser diffuser all devices do not have equal visual impact Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 The Aesthetics of Air Delivery register grille diffuser Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 grille a diffuser provides sophisticated control of air delivery; a register the same but not quite so sophisticated; a grille basically just covers up a hole 11

12 Aesthetic Potential of Exposed Systems Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 23 The Messy Stuff Is Usually Hidden Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12

13 Big Stuff: Plan for It chiller cooling tower you ve got to give innovation credit for the partially earth-bermed cooling tower Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 Really Big Stuff: Seriously Plan for It < penthouse mechanical room > OA duct Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13

14 Creative Design student work: Oklahoma State University Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 27 Creative Design student work: Oklahoma State University Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 28 14