Environmental Controls I/IG Lecture 14 Mechanical System Space Requirements Mechanical System...
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Transcript of Environmental Controls I/IG Lecture 14 Mechanical System Space Requirements Mechanical System...
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
Mechanical Room SizingMechanical Room Sizing Mechanical Room SizingMechanical Room Sizing
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
Mechanical Mechanical Room SizingRoom Sizing
Generally sized based on total floor area in building served
S: p.391, T.10.3
Mechanical Mechanical Room SizingRoom Sizing
Size mechanical room space
ApplicationSquare Footage
S: p.391, T.10.3
Mechanical Mechanical Room SizingRoom Sizing
Sizing Example
150,000 SF Department Store
Mechanical Room: 3,200 sf
S: p. 391, T.10.3
Fan Room SizingFan Room Sizing Fan Room SizingFan Room Sizing
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
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
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
Fan Room Fan Room SizingSizing
Size fan room
ApplicationSquare Footage
S: p. 392, T.10.4
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
Fresh Air InletsFresh Air Inlets
Avoid contamination sources (25’ minimum) Loading docks Smoking areas Cooling Towers Exhaust air outlets Plumbing vents Others…
Mechanical System Mechanical System Exchange Loops Exchange Loops Mechanical System Mechanical System Exchange Loops Exchange Loops
Mechanical System Exchange Mechanical System Exchange LoopsLoops
Heat is removed/ added via heat exchange loops.
S: p. 394, F.10.15
Mechanical System Exchange Mechanical System Exchange LoopsLoops
Cooling Mode
S: p. 394, F.10.15
Mechanical System Exchange Mechanical System Exchange LoopsLoops
Heating Mode
S: p. 394, F.10.15
Cooling TowerCooling Tower Cooling TowerCooling Tower
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
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
Cooling TowerCooling TowerSizingSizing
Sizing Example
150,000 SF Department Store
Cooling Tower: 560 sf
S: p.391, T.10.3
HVAC SystemsHVAC Systems HVAC SystemsHVAC Systems
System TypesSystem Types
All-AirAir-WaterAll-WaterUnitary Refrigerant System
Selection CriteriaSelection Criteria
Control capability and flexibility required
Environmental requirements
Cost of construction Energy consumption System effficiency
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
All-Air SystemsAll-Air Systems
Single zoneTerminal reheat Multizone Dual duct Variable air volume (VAV)
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
Terminal ReheatTerminal Reheat
One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature
Poor energy efficiency
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
Dual DuctDual Duct
One thermostat controls mixing box for each room
Applications requiring precise control of temperature and humidity
Energy inefficientHigh maintenanceExpensive to build
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
Distribution PathsDistribution Paths
Air may be distributed from the ceiling or the floor
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
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
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
All-Water SystemsAll-Water Systems
Heating/cooling media delivered via water only
Advantages: Flexible placement Space heating
Disadvantages: Condensation Noise
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
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