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Technology in Architecture
Lecture 11 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems
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Mechanical Room Sizing
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Mechanical Room Contains primary equipment (boiler, chiller, etc.)
Usually adjacent to other service areas (loading docks, electrical substation, transformer vault, etc.) Generally away from public entry Include space for service/maintenance M: p. 444, F.12.12
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Mechanical Room Sizing
Generally sized based on total floor area in building served M: p.435, F.12.7
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Mechanical Room Sizing
Size mechanical room space Application Square Footage M: p.435, F.12.7
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Mechanical Room Sizing
Sizing Example 150,000 SF Department Store Mechanical Room: 3,200 sf M: p. 435, F.12.7
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Fan Room Sizing
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Fan Rooms Contain secondary equipment (air handlers, heat exchanger, etc.) Usually adjacent to or within area served Include space for service/maintenance M: p. 479, F.12.49
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University of Michigan Hospital,
Fan Rooms Require connection/ access to fresh air Require means of discharging return air/ exhaust air Minimum 25’ distance of fresh air inlet away from contaminant source University of Michigan Hospital, Ann Arbor, MI
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Fan Room Sizing Generally sized based on total floor area of the thermal zone in building served M: p. 436, F.12.8
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Fan Room Sizing Size fan room Application Square Footage
M: p. 436, F.12.8
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Fan Room Sizing Sizing Example 150,000 SF Department Store
Supply/Return Mains: 120 sf for each Fan Room: 5,200 sf Fresh Air Inlet: 500 sf Exhaust Air Outlet: 400 sf M: p. 436, F.12.8
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Fresh Air Inlets Avoid contamination sources (25’ minimum)
Loading docks Smoking areas Cooling Towers Exhaust air outlets Plumbing vents Others…
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Mechanical System Exchange Loops
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Mechanical System Exchange Loops
Heat is removed/ added via heat exchange loops. M: p. 439, F.12.9
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Mechanical System Exchange Loops
Cooling Mode M: p. 439, F.12.9
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Mechanical System Exchange Loops
Heating Mode M: p. 439, F.12.9
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Cooling Tower
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Cooling Tower Divided into a series of cells for redundancy/ serviceability Significant structural load: Rooftop vs At-grade Potential air contamination Locate based on prevailing wind direction M: p.465, F
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University of Michigan Hospital,
Cooling Tower Service access needed for water treatment/debris removal Biocides can cause etching on glass and other surfaces Minimum 25’ distance away fresh air inlet or fenestration University of Michigan Hospital, Ann Arbor, MI
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Cooling Tower Sizing Sizing Example 150,000 SF Department Store
Cooling Tower: 560 sf M: p.435, F.12.7
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HVAC Systems
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System Types All-Air Air-Water All-Water Unitary Refrigerant System
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Selection Criteria Control capability and flexibility required
Environmental requirements Cost of construction Energy consumption System effficiency
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All-Air Systems Heating/cooling media delivered via air only
Advantages: Humidification & Heat recovery Complex zoning Close humidity & temperature control (exc. VAV) Can use outside air for economizer cycle Disadvantages: Special care for maintenance access Supplemental perimeter radiation may be needed Higher volume of space needed
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All-Air Systems Single zone Terminal reheat Multizone Dual duct
Variable air volume (VAV)
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Single Zone One thermostat controls several rooms in a single thermal zone Applications requiring air filtration and humidity control Uneven comfort for multiple rooms
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Terminal Reheat One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature Poor energy efficiency
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Multizone One thermostat controls discharge dampers to adjust air temperature to each room Small buildings with limited distances for duct runs Simultaneous heating and cooling
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Dual Duct One thermostat controls mixing box for each room
Applications requiring precise control of temperature and humidity Energy inefficient High maintenance Expensive to build
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Variable Air Volume One thermostat controls VAV valve for each room and reduces airflow under lower load Applications where loads vary significantly (offices, schools) Poor humidity control Subcooling
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Chilled Beams Source: article.php?L=5&C=463&P=4
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Chilled Beams Source: article.php?L=5&C=463&P=4
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Chilled Beams Integration of geothermal and VAV
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Distribution Paths Air may be distributed from the ceiling or the floor
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Distribution Paths—Ceiling
Conventional distribution is from the ceiling Air discharge: 55ºF Velocity is fpm M: p.544 F
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Distribution Paths—Floor
Also known as displacement cooling Air discharge: 60+ºF Velocity is slower than ceiling discharge Higher ceilings M: p. 559, F M: p. 394, F.10.12
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Air-Water Systems Heating/cooling media delivered via air and water
Advantages: Flexible placement Centralized humidity and filtration Space heating Disadvantages: Condensation Noise Induction Fan Coil Unit M: p. 396, F.10.13
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All-Water Systems Heating/cooling media delivered via water only
Advantages: Flexible placement Space heating Disadvantages: Condensation Noise
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Fan Coil Unit Fan draws air from room across coils Flexible Less space
Low cost Noise Poor ventilation/humidity Maintenance Condensation control Simultaneous heating and cooling M: p. 398, F.10.14
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Unitary Refrigerant System
Heating/cooling media delivered via local equipment Advantages: Individual room control Independent heating and cooling Single zone affected by malfunction Low initial cost Reliability Disadvantages: Short life Noise Humidity control Air filtration Ventilation Through the wall air-conditioning Heat pumps
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ARCH-4372/6372 HVAC Distribution & Sizing HVAC Distribution Systems
Diffuser Selection and Layout Ductwork Sizing
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HVAC Distribution Systems
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Distribution System Plans Symbols
Positive Pressure (supply) Negative Pressure (return or exhaust)
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Distribution System Plans Symbols
Arrow indicates air flow direction
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Distribution System Plans Symbols
Flow patterns 1-way 2-way 3-way 4-way
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Distribution System Plans Symbols
Thermostat Smoke/Fire Damper T
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Distribution System Plans Symbols
Double Line Single Line
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Distribution System Plans Symbols
Section z z 16 x 12 z z 12 x 16
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Distribution System Plans
Double Line Single Line
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Distribution System Plans
Double Line Single Line
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Ceiling Plenum Plans Shows duct path from distribution network to supply diffuser or return register
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Diffuser Selection and Layout
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Diffuser Selection Diffuser Selection Criteria Air flow Throw
Noise Criteria (NC) Level Appearance
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Diffuser Selection Air Flow Throw NC Level
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Diffuser Selection Throw: Avoid Gaps and overlap
Distance of air movement Avoid Gaps and overlap Obstructions/deflectors Velocity (fpm)
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Diffuser Layout 1. Use Room Sensible Load (no latent, no ventilation) to determine air flow Qs=1.08 x CFM x ΔT where ΔT=|Tsa-Tra| thus CFM= Qs (1.08 x ΔT)
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Diffuser Layout 2. Define Supply Air temperatures Heating:
Tsa range is ºF Tra=68ºF Cooling: Tsa range is 45-55ºF Tra=78ºF
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Diffuser Layout 3. Define ΔT Heating: ΔT=|110-68|=42ºF Cooling:
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Diffuser Layout 4. Determine Air Flow (CFM) CFMhtg= Qs (1.08 x ΔThtg)
CFMclg= Qs (1.08 x ΔTclg) Larger result determines air flow
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Diffuser Layout 5. Revise discharge air temperature to match required air flow CFMpeak= Qs (1.08 x |Tsa-Tra|) solve for Tsa
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Diffuser Layout 6. Select diffuser layout Regular pattern
Uniform coverage Avoid “short circuiting” with exhaust/return registers
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Diffuser Layout Example
Office space with overhead heating and cooling supply NC level 35 16’ 8’
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Diffuser Layout Example
Heating Qs= 11,800 Btuh Discharge=110ºF Set point = 68ºF ΔT = 42ºF CFMhtg= Qs (1.08 x ΔT) =11,800/(1.08 x 42)=260 CFM
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Diffuser Layout Example
Cooling Qs=8,600 Btuh; ΔT= 42ºF CFMclg= Qs (1.08 x ΔT) =8,600/(1.08 x 23)=346 CFMHTG= 260 < CFMclg =346
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Diffuser Layout Example
Revise Heating Tsa CFMpeak= Qs (1.08 x ΔT) =346=11,800/(1.08 x |Tsa-68|) Tsa=99.6ºF
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Diffuser Layout Example
Define Pattern 346 Cfm Round up to 0 or 5 cfm cfm cfm cfm cfm
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Diffuser Layout Example
Define Pattern 346 Cfm Round up to 0 or 5 cfm cfm 2-way cfm 4-way cfm 3-way cfm 2-way 16’ 8’
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Diffuser Selection NC 35 Air Flow Throw Select 8” Rd 4-way
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Diffuser Layout Example
Define Pattern 346 Cfm cfm 4-way 4’ 4’ 4’ 4’ 16’ 4’ 4’ 4’ 4’ 8’
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Return Register Selection
Selection Criteria Air flow Noise Criteria (NC) Level Appearance
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Return Register Selection
Air Flow NC Level
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Return Register Layout
Avoid Short circuiting with supply diffusers Locating in visually obtrusive location
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Return Register Layout
Define Pattern Supply=350 cfm Return cfm 16’ 8’
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Return Register Selection
Air Flow 350 cfm NC Level 35 Select 10” x 8” 350 cfm NC 27db
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Return Register Layout
8’ 16’ Define Pattern Supply=350 cfm Return cfm 10” x 8” NC 27db
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