Technology in Architecture Lecture 11 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems

Mechanical Room Sizing

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

Mechanical Room Sizing Generally sized based on total floor area in building served M: p.435, F.12.7

Mechanical Room Sizing Size mechanical room space Application Square Footage M: p.435, F.12.7

Mechanical Room Sizing Sizing Example 150,000 SF Department Store Mechanical Room: 3,200 sf M: p. 435, F.12.7

Fan Room Sizing

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

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

Fan Room Sizing Generally sized based on total floor area of the thermal zone in building served M: p. 436, F.12.8

Fan Room Sizing Size fan room Application Square Footage M: p. 436, F.12.8

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

Fresh Air Inlets Avoid contamination sources (25’ minimum) Loading docks Smoking areas Cooling Towers Exhaust air outlets Plumbing vents Others…

Mechanical System Exchange Loops

Mechanical System Exchange Loops Heat is removed/ added via heat exchange loops. M: p. 439, F.12.9

Mechanical System Exchange Loops Cooling Mode M: p. 439, F.12.9

Mechanical System Exchange Loops Heating Mode M: p. 439, F.12.9

Cooling Tower

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. 12.36

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

Cooling Tower Sizing Sizing Example 150,000 SF Department Store Cooling Tower: 560 sf M: p.435, F.12.7

HVAC Systems

System Types All-Air Air-Water All-Water Unitary Refrigerant System

Selection Criteria Control capability and flexibility required Environmental requirements Cost of construction Energy consumption System effficiency

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

All-Air Systems Single zone Terminal reheat Multizone Dual duct Variable air volume (VAV)

Single Zone One thermostat controls several rooms in a single thermal zone Applications requiring air filtration and humidity control Uneven comfort for multiple rooms

Terminal Reheat One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature Poor energy efficiency

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

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

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

Chilled Beams Source: http://continuingeducation.construction.com/ article.php?L=5&C=463&P=4

Chilled Beams Source: http://continuingeducation.construction.com/ article.php?L=5&C=463&P=4

Chilled Beams Integration of geothermal and VAV

Distribution Paths Air may be distributed from the ceiling or the floor

Distribution Paths—Ceiling Conventional distribution is from the ceiling Air discharge: 55ºF Velocity is 100-500 fpm M: p.544 F.12.106

Distribution Paths—Floor Also known as displacement cooling Air discharge: 60+ºF Velocity is slower than ceiling discharge Higher ceilings M: p. 559, F.12.120 M: p. 394, F.10.12

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

All-Water Systems Heating/cooling media delivered via water only Advantages: Flexible placement Space heating Disadvantages: Condensation Noise

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

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

ARCH-4372/6372 HVAC Distribution & Sizing HVAC Distribution Systems Diffuser Selection and Layout Ductwork Sizing

HVAC Distribution Systems

Distribution System Plans Symbols Positive Pressure (supply) Negative Pressure (return or exhaust)

Distribution System Plans Symbols Arrow indicates air flow direction

Distribution System Plans Symbols Flow patterns 1-way 2-way 3-way 4-way

Distribution System Plans Symbols Thermostat Smoke/Fire Damper T

Distribution System Plans Symbols Double Line Single Line

Distribution System Plans Symbols Section z z 16 x 12 z z 12 x 16

Distribution System Plans Double Line Single Line

Distribution System Plans Double Line Single Line

Ceiling Plenum Plans Shows duct path from distribution network to supply diffuser or return register

Diffuser Selection and Layout

Diffuser Selection Diffuser Selection Criteria Air flow Throw Noise Criteria (NC) Level Appearance

Diffuser Selection Air Flow Throw NC Level

Diffuser Selection Throw: Avoid Gaps and overlap Distance of air movement Avoid Gaps and overlap Obstructions/deflectors Velocity (fpm) 150 100 50

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)

Diffuser Layout 2. Define Supply Air temperatures Heating: Tsa range is 90-110ºF Tra=68ºF Cooling: Tsa range is 45-55ºF Tra=78ºF

Diffuser Layout 3. Define ΔT Heating: ΔT=|110-68|=42ºF Cooling:

Diffuser Layout 4. Determine Air Flow (CFM) CFMhtg= Qs (1.08 x ΔThtg) CFMclg= Qs (1.08 x ΔTclg) Larger result determines air flow

Diffuser Layout 5. Revise discharge air temperature to match required air flow CFMpeak= Qs (1.08 x |Tsa-Tra|) solve for Tsa

Diffuser Layout 6. Select diffuser layout Regular pattern Uniform coverage Avoid “short circuiting” with exhaust/return registers

Diffuser Layout Example Office space with overhead heating and cooling supply NC level 35 16’ 8’

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

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

Diffuser Layout Example Revise Heating Tsa CFMpeak= Qs (1.08 x ΔT) =346=11,800/(1.08 x |Tsa-68|) Tsa=99.6ºF

Diffuser Layout Example Define Pattern 346 Cfm Round up to 0 or 5 cfm 1@350 cfm 2@175=350 cfm 3@115=345 cfm 4@90=360 cfm

Diffuser Layout Example Define Pattern 346 Cfm Round up to 0 or 5 cfm 1@350 cfm 2-way 2@175=350 cfm 4-way 3@115=345 cfm 3-way 4@90=360 cfm 2-way 16’ 8’

Diffuser Selection NC 35 Air Flow Throw Select 8” Rd 4-way

Diffuser Layout Example Define Pattern 346 Cfm 2@175=350 cfm 4-way 4’ 4’ 4’ 4’ 16’ 4’ 4’ 4’ 4’ 8’

Return Register Selection Selection Criteria Air flow Noise Criteria (NC) Level Appearance

Return Register Selection Air Flow NC Level

Return Register Layout Avoid Short circuiting with supply diffusers Locating in visually obtrusive location

Return Register Layout Define Pattern Supply=350 cfm Return 1@350=350 cfm 16’ 8’

Return Register Selection Air Flow 350 cfm NC Level 35 Select 10” x 8” 350 cfm NC 27db

Return Register Layout 8’ 16’ Define Pattern Supply=350 cfm Return 1@350=350 cfm 10” x 8” NC 27db