1
Q
HVAC Sizing Factors
A
- What’s the capacity required for heating & cooling equipment?
- What’s the size of the equipment?
- What size & layout are the distribution pipes & ducts?
2
Q
Factors determining HVAC Capacity
A
- Total heat gains & losses in most extreme conditions
- Active, passive, or combination system?
3
Q
Variables affecting HVAC space requirements
A
- Scope of system (local, centralized, district)
- Type of system
- Building size
- Building type
- Presence of passive systems
4
Q
Local system
A
- Generally serves 1 zone
- Used for small buildings or areas of buildings
- Ex: residential furnace, window-mounted AC or wall-mounted minisplit
5
Q
Centralized system
A
- Serves several zones from 1 location
- Commercial & institutional buildings, mid-larges size
- Ex: Boilers, chillers, pumps, etc. in one location with distribution components
- Requires the most space in-building
6
Q
District System
A
- Heating/cooling for several buildings served by single plant
- Ex: central steam plant on a campus
- Requires the least space in-building
7
Q
All-air HVAC system
A
- Needs the most space
- AHUs, large distribution & return ductwork
8
Q
All-water HVAC system
A
- Least amount of space, uses water pipes; no supply air ducts
- Ventilation provided thru wall at each fan coil unit
9
Q
Air-water HVAC system
A
- Generally no return air ducts
- If returns needed, generally collected in plenums, not separate ducts
10
Q
Preliminary sizing of Mech room as % of building served
A
All-air or air-water system:
3%-10%
All-water system:
1%-3%
11
Q
AHU
A
- Air Handling Unit
- Uses water from boilers/chillers to heat/cool air
- Located in fan room
12
Q
Fan Room
A
- Houses AHU
- Ideally next to exterior wall; otherwise requires fresh air to be fed in
- Addtl equipment: fans, filters, humidifiers, preheat coils, return air ducts, outside air intakes, exhaust ports, dampers, mixing box
- Room should be acoustically separated/dampened
- Service doors/ access panels need to be sized to accommodate equipment replacement
13
Q
Static head
A
- AKA Static Pressure
- Amount of pressure that must be applied to overcome baseline frictional resistance inside duct/pipe, measured in inches of water
14
Q
Fan room location impacts
A
- Location should minimize length of ductwork as much as possible
- More duct = More static head = more fans needed
15
Q
Preliminary duct space sizing metric
A
- 10sf-20sf cross-sectional area per every 10,000sf floor area served
- Includes supply & return ducts
- High-pressure ducts will take up less space
16
Q
Chase
A
- Fully enclosed shaft that only contains ducts or piping
17
Q
Mixing Box
A
- Controls air that flows into a space from main air supply line
- Tied to thermostat
18
Q
Terminal Reheat System
A
- Cool air enters mixing box at fixed temp
- Mixing box contains hot water coil to heat air if needed
- Can be identified by air ducts & copper pipes going into mixing boxes
19
Q
Dual-Duct System
A
- Mixing box receives cool air & hot air from separate ducts
- Mixes air to obtain desired temp & distributes
20
Q
Variable Air Volume System
A
- VAV system, VAV box
- Air enters VAV box at constant temp
- Airflow rate to space is controlled
- 1 duct in, 1 duct out
21
Q
Access Flooring
A
- False floor composed of removable panels raised above structural floor
- Usually used for electrical/ data/ comms wiring, can be used for HVAC ducts
22
Q
Plenum
A
- Space between suspended ceiling and structure above
- Account for sprinklers & recessed lights when calculating
23
Q
Water Supply Pressure
A
- City mains usually 50psi
- Take off friction in the system, must still have enough pressure to service system
24
Q
Static Head to PSI
A
1ft = .433 psi
- .433 psi is the pr3 ic head
25
Upfeed System Water Supply
- Uses pressure in water main to directly supply fixtures
- Height limit 40ft-60ft
26
Downfeed System Water Supply
- Water from main pumped to storage tanks near top of building/ top of the part served by the system, then gravity fed to fixtures
- Pressure at any fixture = vertical distance from outlet of the tank to fixture at .433 psi/ft
- Limited by max allowable pressure at fixtures at bottom of the zone, allowing for friction loss in piping
- Max pressure genearlly 45psi-60psi, ie 138ft
- Pressure-reducing valves required beyond this height
- Min distance b/w water source & uppermost fixtures need to be maintained to provide required pressure
27
Direct Upfeed Pumping System
- AKA tankless system
- Several pumps used together and controlled by a pressure sensor
- One sensor constantly runs
- As demand increases, pressure sensors detect pressure drop and more pumps come online as needed
28
Copper Pipe Grades
- K: thickest walls, comes in straight lengths (hard temper) or coils (soft temper); used for underground supply pipe where more strength is needed
- L: Thinner walls than K, also comes straight or coiled; most commonly used for most of the plumbing systems
- M: Thinnest walls, comes in straight length only; Only used in low pressure applications
- Ex: branch supply, chilled water systems, exposed lines, drainage piping
29
DWV Copper
- Drain-Waste-Vent copper
- Rarely used, only in application where pressure is not a concern
30
Steel pipe application
- Used where water isn't corrosive
- More difficult to assemble due to screw fittings
- Schedule numbers indicate wall thickness
- Schedule 40 most commonly used
31
Plastic pipe application
- Check code to see if use restricted to certain functions or construction types
- ABS, CPVC, PE, PEX types
- Rigid & Flexible types
- Pros: Flexibility, light weight, low thermal conductivity, resistance to freezing & scale building, price point, and less noise
32
Union (fitting)
- Fitting type that connects two rigid sections of pipe
- Easily unscrew to allow for repairs or additions to system
33
Compression fittings
- Connections between small-diameter pipes connecting bath & kitchen fixtures
34
Valves
- Used to control water flow
- At risers, horizontal branch lines, pipe connections to fixtures & equipment
- Allow selective shutdown of system for repairs
35
Gate Valve
- Metal wedge against 2 metal parts of valve
- Control on/off
- No turns; low friction loss
36
Globe valve
- Water flow needs to be variable & frequently controlled
- Handle operation; controls compression of washer against metal seat
- 2 right angles; high friction loss
- Faucets, hose bibs, etc.
37
Check valve
- Automatic
- Allows water flow in only one direction (backflow prevention devices, etc)
38
Plumbing System Design Principal
- Pressure needed at most remote fixture added to all pressure losses must not exceed the water main pressure
39
Demand load
- Flow rate that would be needed if all fixtures were in use at once
40
Fixture unit
- Unit flow rate approx. 1cuft/min
41
Pipe Sizing
- Find probable demand in gpm
- Read across flow cart to locate intersection be/ pipe size & demand
42
Probable Demand
- Max flow rate expected under typical conditions
- Tables will provide translation of demand load in FU into probable demand
43
Water Velocity
- Flow is too loud for most situations above 10 ft/sec
- For sound-sensitive situations, anything above 6 ft/sec may be too loud
44
Expansion fittings
- In-line expansion fittings do not require extra space
- Accommodates thermal expansion of pipes
45
Tensiometer
- Measures moisture content of soil at root zones
46
Two-Pipe Circulating System
- All fixtures connected to supply & return pipe
- Natural convection keeps water circulating in system
- Horizontal buildings require pump to circulate
47
Recovery rate
- Number of gallons per hour of cold water that can be heated to desired temperature
48
Heating Systems (hot water)
- Storage tank | Tankless | Circulating
49
Storage tank system
- Same tank used to heat water & store it for use
50
Tankless system
- Water heated as needed & sent to where needed
51
Circulating System
- Water is heated & moved to tank for storage
- Common in commercial systems & solar systems
52
Traps
- Catches & holds some water to form a seal that prevents sewage gasses from coming back up the pipes
- Generally installed within 2 ft of fixture
53
Vents
- Pipes that lead from drainage system to outside air
- Allows built-up sewage gasses to escape
- Allows pressure to equalize so waste drainage doesn't create a siphon that sucks water out of the traps
54
Stacks
- Stack: Vertical pipe that carries wastewater down
- Soil Stack: Waste stack that carries water with human waste
55
House Drain
- Horizontal drain that picks up all the stacks and carries it to a point 3 ft outside building
56
House Sewer
- Horizontal that connects house drain to main sewer line
57
Cleanouts
- Required outside building for house sewer
- Provided where stack connects with house drain
58
Horiz drain slope
- 1/4 in/ft, min
- 1/8 in/ft for pipes larger than 3" diameter
59
Land Slope Away from foundation
- 1/2" per foot
60
PPD
flashcards
Decks in class (15)
# Cards
-
Integration of Systems60
-
Specialty Systems52
-
Structural Fundamentals5
-
Soils & Foundations17
-
Fire Safety1
-
Connections17
-
Loads on Buildings0
-
Project Manual & Specs0
-
Building Code Requirements on Structural Design0
-
Wood Construction4
-
Steel Construction0
-
Concrete Construction0
-
Walls0
-
Lateral Forces - Wind & Earthquakes0
-
Cost Estimates0
