HVAC SYSTEM DESIGN PROCESS

Transcription

1 HVAC SYSTEM DESIGN PROCESS Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 HVAC System Design Process Establish design issues/intents/criteria (including code/standard compliance) Establish zoning requirements Make a preliminary system selection based on the above Calculate design heating/cooling loads Select appropriate source equipment (to meet loads, intent and context) Select appropriate distribution approach (to meet intents and fit context) Coordinate HVAC components with other building systems Run energy analyses to optimize selections Size equipment (fans, pumps, valves, dampers, pipes, ducts, condensers, airhandlers, tanks, ) Coordinate 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 owner red = architect blue = engineer with architect black = engineer Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1

2 HVAC System Selection Process Carefully consider potential design issues Clearly define design intents Establish usable design criteria Compare potential systems against criteria Select best system Validate system selection collectively, the first three become the Owner s Project Requirements (OPR) for climate control and IAQ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 Common HVAC Selection Issues First cost Life-cycle cost Durability Maintainability Reliability Appearance Zoning capabilities Flexibility Energy efficiency Green-ness Noise Space requirements Smoke control capabilities Fuel(s) Owner dictates Many others Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2

3 Common HVAC Design Intents Provide thermal comfort Provide acceptable IAQ Low first cost Good energy efficiency No equipment located 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 5 Match Design Criteria to 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 precedents the criteria shown above are simply examples, from a world of possibilities Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 3

4 Selection Matrix (a design tool) INTENT WEIGHT SCORE SYSTEM A WEIGHTED SCORE SYSTEM A SCORE SYSTEM B WEIGHTED SCORE SYSTEM B Low First Cost Good Energy Efficiency High Flexibility 10 * Clean Appearance Good IAQ Capabilities 9 ** 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 7 Key HVAC Coordination Issues Equipment Locations Source equipment (noise, maintenance access, access for replacement, connection to utilities) Condenser (must be exterior, noise, appearance, air flow, spray) Air-handlers (air supply and return paths, outdoor air access, noise, vibration) Terminal devices (maintenance access, noise) Outdoor air intakes (able to provide fresh OA air) Floor Area for Equipment Mechanical room(s), satellite 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 8 4

5 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 The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 Required Equipment Locations zone diffusers are laid out for reasonable air distribution undifferentiated supply air box MUST be in this area zone-differentiated supply air The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5

6 Large Equipment Areas for schematic planning: can estimate central plant at 7% +/- of conditioned floor area The Architect s Studio Companion: 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 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 12 6

7 Consider Volume (not just floor area) The Architect s Studio Companion, 3rd Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 Volume Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 7

8 Volume Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 Provide for Access Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8

9 Estimating Duct Sizes Assume 1 cfm per square foot (for an all-air system) Duct volume (in ft 2 ) = air flow (in cfm) / air speed (in fpm) Assume 1000 fpm air speed cfm = cubic feet per minute (air flow rate) fpm = feet per minute (air speed in ducts) 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 17 Estimating Duct Sizes Assume a 200 sq ft office (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. Assume a 3000 sq ft classroom wing (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 18 9

10 The Aesthetics of Air Delivery register diffuser diffuser diffuser all devices do not have equal visual impact Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 The Aesthetics of Air Delivery grille register diffuser Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 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 10

11 Aesthetic Potential of Exposed Systems Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 Messy Stuff: is usually hidden Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 11

12 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 23 Really Big Stuff: seriously plan for it < penthouse mechanical room > OA duct Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12

13 Creative Design student work: Oklahoma State University Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 Creative Design student work: Oklahoma State University Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13