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

2. Mechanical Room Sizing Mechanical Room Sizing

3. 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

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

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

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

7. Fan Room Sizing Fan Room Sizing

8. 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

9. 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

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

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

12. 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

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

14. Mechanical System Exchange Loops Mechanical System Exchange Loops

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

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

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

18. Cooling Tower Cooling Tower

19. 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

20. 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

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

22. HVAC Systems HVAC Systems

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

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

25. 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

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

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

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

29. 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

30. 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

31. 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

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

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

34. Chilled Beams Integration of geothermal and VAV

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

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

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

38. 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

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

40. 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

41. 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

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

43. HVAC Distribution Systems

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

45. Arrow indicates air flow direction Distribution System Plans Symbols

46. Flow patterns 1-way 4-way 2-way 3-way

47. Thermostat Smoke/Fire Damper Distribution System Plans Symbols T

48. Double Line Single Line Distribution System Plans Symbols

49. Plan Section Distribution System Plans Symbols zz z z 12 x 16 16 x 12

50. Distribution System Plans Double Line Single Line

51. Distribution System Plans Double Line Single Line

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

53. Diffuser Selection and Layout

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

55. Diffuser Selection Air Flow Throw NC Level

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

57. Diffuser Layout 1. Use Room Sensible Load (no latent, no ventilation) to determine air flow Q s =1.08 x CFM x ΔT where ΔT=|T sa -T ra | thus CFM= Qs (1.08 x ΔT)

58. Diffuser Layout 2. Define Supply Air temperatures Heating: T sa range is 90-110ºF T ra =68ºF Cooling: T sa range is 45-55ºF T ra =78ºF

59. Diffuser Layout 3. Define ΔT Heating: ΔT=|110-68|=42ºF Cooling: ΔT=|55-78|=23ºF

60. Diffuser Layout 4. Determine Air Flow (CFM) CFM htg = Qs (1.08 x ΔT htg ) CFM clg = Qs (1.08 x ΔT clg ) Larger result determines air flow

61. Diffuser Layout 5. Revise discharge air temperature to match required air flow CFM peak = Qs (1.08 x |T sa- T ra |) solve for T sa

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

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

64. Diffuser Layout Example Heating Qs= 11,800 Btuh Discharge=110ºF Set point = 68ºF ΔT = 42ºF CFM htg = Qs (1.08 x ΔT) =11,800/(1.08 x 42)=260 CFM

65. Diffuser Layout Example Cooling Qs=8,600 Btuh; ΔT= 42ºF CFM clg = Qs (1.08 x ΔT) =8,600/(1.08 x 23)=346 CFM HTG = 260 < CFM clg =346

66. Diffuser Layout Example Revise Heating T sa CFM peak = Qs (1.08 x ΔT) =346=11,800/(1.08 x |T sa -68|) T sa =99.6ºF

67. 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

68. 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 Diffuser Layout Example 8’ 16’

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

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

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

72. Return Register Selection Air Flow NC Level

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

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

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

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

77. Ductwork Sizing

78. Volume (Q) is a function of cross sectional area (A) and velocity (V) Q=AV however, momentum, friction and turbulence must also be accounted for in the sizing method

79. Momentum As air leaves fan, centrifugal motion creates momentum FAN

80. Friction As air moves along a duct, friction slows the velocity at the edges FAN

81. Turbulence As ducts change direction or cross-sectional dimensions, turbulence is created FAN

82. Static Pressure Force required to overcome friction and loss of momentum due to turbulence As air encounters friction or turbulence, static pressure is reduced Fans add static pressure

83. Pressure Measurement Static pressure is measured in inches of force against a water column Inches-water gauge Positive pressure pushes air Negative pressure draws air

84. Pressure Measurement Straight ducts have a pressure loss of “w.g./100’ based on diameter and velocity

85. Friction Loss Chart What is the pressure loss/100 ft in a 12” diameter duct delivering 1000 cfm of air? Velocity? RR-6 0.2”/100 FT 1325 fpm

86. Equivalent Length Describes the amount of static pressure lost in a fitting that would be comparable to a length of straight duct RR-6

87. Ductwork Comparison Round ductwork is the most efficient but requires greater depth Rectangular ductwork is the least efficient but can be reduced in depth to accommodate smaller clearances Avoid aspect ratios greater than 5:1

88. Equal Friction Method Presumes that friction in ductwork can be balanced to allow uniform friction loss through all branches

89. Equal Friction Method 1. Find effective length (EL) of longest run 2. Establish allowed static pressure loss/100’ ΔP=100(SP)/EL 3. Size ducts 4. Repeat for each branch Note: velocity must be higher in each upstream section

90. Equal Friction Method Example Size ductwork serving office diffusers from earlier example Elbow equivalent length: 10’ Straight fitting equiv. length: 5’ AHU connection: 50’ AHU 4’ 6’ 30’ 12’ 8’ 6’ 175 cfm (typ.)

91. Equal Friction Method Example Supply Diffuser pressure loss: 0.038” Return Register pressure loss: 0.159” Fan: 0.535”w.g. (75% for supply)

92. Equal Friction Method 1. Find effective length of longest run Identify longest run Label duct sections AHU 4’ 6’ 30’ 12’ 8’ 6’ 175 cfm (typ.) 1 23 4

93. Worksheet Duct ActualEquivEffectiveAirΔPDuctAir SectionLengthLengthLengthVol.”/100’DiamVelocity 16’10’16’175 28’5’13’175 312’5’17’350 430’50’80’700 56’70’126’ AHU 4’ 6’ 30’ 12’ 8’ 6’ 175 cfm (typ.) 1 23 4

94. Equal Friction Method 2. Establish allowed static pressure loss/100’ Fan SP: 0.533” -Supply Diff: 0.038” -Return Reg:0.159” Available: 0.336” x 0.75=0.252” ΔP/100’=100(SP)/EL = 100(.252)/126= 0.2”/100’

95. Worksheet Duct ActualEquivEffectiveAirΔPDuctAir SectionLengthLengthLengthVol.”/100’DiamVelocity 16’10’16’1750.2 28’5’13’1750.2 312’5’17’3500.2 430’50’80’7000.2 56’70’126’ AHU 4’ 6’ 30’ 12’ 8’ 6’ 175 cfm (typ.) 1 23 4

96. Equal Friction Method 3. Size ducts RR-6

97. Equal Friction Method 3. Size ducts 1 175cfm 7” diam @ 620 fpm 2 175cfm7” diam @ 620 fpm 3 350 cfm 9” diam @ 800 fpm 4 700 cfm 12” diam @ 900 fpm

98. Worksheet Duct ActualEquivEffectiveAirΔPDuctAir SectionLengthLengthLengthVol.”/100’DiamVelocity 16’10’16’1750.27”620 fpm 28’5’13’1750.27”620 fpm 312’5’17’3500.29”800 fpm 430’50’80’7000.212”900 fpm 56’70’126’ AHU 4’ 6’ 30’ 12’ 8’ 6’ 175 cfm (typ.) 1 23 4