environmental controls i/ig lecture 14 mechanical system space requirements mechanical system...
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![Page 1: Environmental Controls I/IG Lecture 14 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems Lecture 14 Mechanical System](https://reader035.vdocument.in/reader035/viewer/2022070411/56649c7f5503460f94935d32/html5/thumbnails/1.jpg)
Environmental Controls I/IGEnvironmental Controls I/IGEnvironmental Controls I/IGEnvironmental Controls I/IG
Lecture 14Mechanical System Space
RequirementsMechanical System Exchange Loops
HVAC Systems
Lecture 14Mechanical System Space
RequirementsMechanical System Exchange Loops
HVAC Systems
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Mechanical Room SizingMechanical Room Sizing Mechanical Room SizingMechanical Room Sizing
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Mechanical RoomMechanical RoomContains 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
S: p. 398, F.10.18
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Mechanical Mechanical Room SizingRoom Sizing
Generally sized based on total floor area in building served
S: p.391, T.10.3
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Mechanical Mechanical Room SizingRoom Sizing
Size mechanical room space
ApplicationSquare Footage
S: p.391, T.10.3
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Mechanical Mechanical Room SizingRoom Sizing
Sizing Example
150,000 SF Department Store
Mechanical Room: 3,200 sf
S: p. 391, T.10.3
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Fan Room SizingFan Room Sizing Fan Room SizingFan Room Sizing
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Fan RoomsFan Rooms
Contain secondary equipment (air handlers, heat exchanger, etc.)
Usually adjacent to or within area served
Include space for service/maintenance
S: p. 418, F.10.42
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Fan RoomsFan 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 Fan Room SizingSizing
Generally sized based on total floor area of the thermal zone in building served
S: p. 392, T.10.4
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Fan Room Fan Room SizingSizing
Size fan room
ApplicationSquare Footage
S: p. 392, T.10.4
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Fan Room Fan Room SizingSizing
Sizing Example
150,000 SF Department Store
Fan Room: 5,200 sf
Fresh Air Inlet: 550 sf
Exhaust Air Outlet: 450 sf
S: p. 392, T.10.4
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Fresh Air InletsFresh 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 Mechanical System Exchange Loops Exchange Loops Mechanical System Mechanical System Exchange Loops Exchange Loops
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Mechanical System Exchange Mechanical System Exchange LoopsLoops
Heat is removed/ added via heat exchange loops.
S: p. 394, F.10.15
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Mechanical System Exchange Mechanical System Exchange LoopsLoops
Cooling Mode
S: p. 394, F.10.15
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Mechanical System Exchange Mechanical System Exchange LoopsLoops
Heating Mode
S: p. 394, F.10.15
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Cooling TowerCooling Tower Cooling TowerCooling Tower
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Cooling TowerCooling 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
S: p.407, F. 10.30
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Cooling TowerCooling 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 TowerCooling TowerSizingSizing
Sizing Example
150,000 SF Department Store
Cooling Tower: 560 sf
S: p.391, T.10.3
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HVAC SystemsHVAC Systems HVAC SystemsHVAC Systems
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System TypesSystem Types
All-AirAir-WaterAll-WaterUnitary Refrigerant System
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Selection CriteriaSelection Criteria
Control capability and flexibility required
Environmental requirements
Cost of construction Energy consumption System effficiency
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All-Air SystemsAll-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 SystemsAll-Air Systems
Single zoneTerminal reheat Multizone Dual duct Variable air volume (VAV)
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Single ZoneSingle 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 ReheatTerminal 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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MultizoneMultizone
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 DuctDual Duct
One thermostat controls mixing box for each room
Applications requiring precise control of temperature and humidity
Energy inefficientHigh maintenanceExpensive to build
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Variable Air VolumeVariable 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 controlSubcooling
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Distribution PathsDistribution Paths
Air may be distributed from the ceiling or the floor
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Distribution Paths—Ceiling Distribution Paths—Ceiling
Conventional distribution is from the ceiling
Air discharge: 55ºFVelocity is 100-500 fpm
S: p.431 F.10.54
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Distribution Paths—Floor Distribution Paths—Floor
Also known as displacement cooling
Air discharge: 60+ºFVelocity is slower than ceiling discharge
Higher ceilings
S: p. 387, F.10.12
S: p. 425, F.10.48
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Air-Water SystemsAir-Water SystemsHeating/cooling media delivered via air and water
Advantages: Flexible placement Centralized humidity and filtration Space heating
Disadvantages: Condensation Noise
Induction
Fan Coil Unit
S: p. 388, F.10.13
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All-Water SystemsAll-Water Systems
Heating/cooling media delivered via water only
Advantages: Flexible placement Space heating
Disadvantages: Condensation Noise
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Fan Coil UnitFan Coil UnitFan draws air from room across coils
FlexibleLess spaceLow cost
NoisePoor ventilation/humidityMaintenanceCondensation controlSimultaneous heating and cooling
S: p. 390, F.10.14
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Unitary Refrigerant SystemUnitary Refrigerant SystemHeating/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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