Systems Flashcards
skin load dominated building
have a lot of surface volume relative to their volume, thermal response is heavily influenced by the conditions outsid
internal load dominated building
minimal surface area relative to volume (hospitals, skyscrapers, office buildings) or buildings that generate a lot of heat regardless of their volume (theater while in use, factory) aka have a lot of loads. Only need heating on worst winter nights, and around the perimeter. It’s more about shedding heat year round
Solar heat gain coefficient
the fraction of net solar radiation through a window, both directly transmitted and absorbed and subsequently released inward
ranges from 0 - 1, higher means more of radiant heat goes through
Typ high is 0.7 - 0.9, low is 0.2 - 0.4
solar insolation
radiant energy per sf of the sun
British Thermal Unit (BTU)
the heat needed to move 1 lb of water up 1 degree F
Psychrometry
relation between air temperature and humidity
When things evaporate, they make everything around them colder
Warm air can hold more moisture than cool air
degree days
a unit used to determine the heating requirements of buildings, representing a fall of one degree below a specified average outdoor temperature (65°F) for one day
The higher the CDD, the longer or hotter the summer
The higher the HDD number the most severe the winter
Conductivity (k)
the rate at which heat passes through a specified material
- higher conductivity the faster heat moves across
Resistivity (r)
the rate at which a material resists the transfer of heat
-inverse of conductivity, 1/r
-we generally want materials with high r
-can be higher than 1
Conductance (C)
homogeneous materials of any given thickness or for heterogeneous materials with known thermal properties
Resistance (R)
homogeneous materials of any given thickness or for heterogeneous materials with known thermal properties
- Inverse of conductance
- R = r x d
U Value
measure of the overall ability of a series of conductive and convective barriers to transfer heat
value between 1 & 0
the lower the value, the better the insulator
U = 1 / R1 + R2 + R3 + …
Conduction (including equation)
heat exchange between two surfaces that are in contact
-heat will move as a function of the temperature difference between the two surfaces (delta T), the area of the surfaces that are touching (A), and the U Value of the materials touching
Q=UxAxdeltaT
Outdoor Design Temperature
worst case scenarios seasonal low, similar to 100 year flood
Allows to calculate what equipment you need to heat on the coldest day
Air change
rate per hour at which an entire volume of air leaves and is replaced by outside air
-0.9 air change means 90% in one hour
-Need to convert air change per hour to cubic ft or air per minute
-2 is good amount, anything below 0.3 you have to intentionally bring in outside air
Radiation
thermal radiation is electromagnetic radiatoin generated by the thermal motion of charged particles
-Ex. surfaces around you have higher temps than the air - higher radiant heat
Absorptance
dark and matte surfaces absorb more heat. Light or reflective material reflect heat
Emittance
a material’s ability to release heat through radiation
Low E Glass
microscopic layer of reflective coating inside glass
reflects heat back inside during winter, reflects heat out in the summer
Thermal Mass
the ability of a material to absorb, store and release heat
-Thermal lag - peaks are later and less sharp
-Moderating effect takes severity out of temp swings
3 types of passive solar gain
Direct gain space - you are occupying the space that’s being heated up
Indirect gain space - solar energy heating up a gap between window and concrete wall (Trombe wall), thermal mass has a good view of the sun
Sun space - also indirect, sun heats up one space, which is not conditioned, conditioned space is inboard of that
evaporator loop
Coolant that is evaporating or boiling is cold
Low pressure induces boiling
The side that is typ inside the house
condenser loop
Coolant that is condensing is warm (heat is produced when changing from gas to liquid)
High pressure induces condensation
The side that is typ outside the house
economizer cycle / free cooling
Cooling large buildings on cold nights with cool air using cold air outside the building (need to cool b/c heat generated inside the building offsets some of the heat losses from the envelope)
Can be air or water
heat pump
Reverse flow of coolant so cold side is outside and hot side is inside
can be geothermal
grille
air goes in
register
air goes out
diffuser
air is spread out
heat exchanger
allows heat from the exhaust air to be shared with the intake air, without coming into direct contact
single zone HVAC
se one outdoor condenser and one indoor head for a single area of the home
ideal for small homes
Terminal Reheat (with VAV)
If a room needs to be heated, a valve opens to allow heating water to flow through the reheat coil which reheats the air that passes through the coil. The controls that monitor air flow and heating coil are normally linked to the room’s thermostat.
advantages are lots of control & space and equipment efficiencies, disadvantages are wasted energy
Dual Duct system
not really used anymore, have one hot duct and one cold, mix together in a mixing box per room to achieve desired temp
split system
compressor and condenser are outside, evaporator is inside, mostly for residential, must keep evaporator within 100’ of eachother
fan coil unit
Fan in the space rather than remotely, generally minimal ductwork, but noisier, efficiency and maintenance, increase control, need less space (pipes rather than ducts), common for multifam
Evaporative condenser
water sprayed over top of the condenser, helps cool it quicker aka more efficient
Issues with putting equip on the roof
Structural demands, noisier, ugly, inefficient because heat/cool loss as you run things across the roof
Minisplit
Fan coil unit in each zone, and each can be either a condenser or evaporator when needed
Rooftop Water to Water System
Chiller using water to cool the condenser (cooling tower) bring cool to building through chilled pipes
Can have the chiller be remote (up to ½ mi away) and feed multiple bldgs
Can have chiller in the basement and cooling tower on roof
Could be geothermal water to water - condenser heat goes through pipes in ground to cool/heat depending on season
Rooftop Water to Air System
Condenser side has water cooled by water tower, evaporator has fan blowing air over coils
types of pipes
Copper - more expensive, more friction
Plastic - less expensive, less friction (ABS, PE, PVC, PVDC - can be used with hot water)
rated by thickness (k thicker, l medium, m thinner)
DWV - used for drains and vents
types of valves
Gate - used for maintenance, can open it completely or close it
Globe - used for faucets, repeated use
Check - used for backflow prevention, near where water enters the bldg
Pressure equation
Pressure (P, psi) = 0.433 (constant) x Height (h, ft)
hot water requirements
140 deg for kitchen and laundry
110 deg for shower
105 for handwashing
types of vents
Traps require vents, some can share, some need their own
Soil stack - black water
Stack vent - vent above the soil stack, lavatory, etc
Waste stack - grey water
Vent stack - not directly above stack, off to the side
septic system
Solids are anaerobic decomposed, liquids to a leach field
Different types of soil absorb at different rates. Need percolation (perc) test
Artesian well
comes from an aquifer under positive pressure (earth on top of the water is so much that if you stick a pipe down into it, the water will come up)
shallow well
single straw down to water (up to 25’) sucks water from underground
deep well
deeper than 25’, uses deep well pump, sends some low pressure water down into the well, uses venturi effect to suck water up
1, 2, 4 pipe systems
1 pipe system - water is not as hot near end of loop, but has a control valve so you can turn on / off different zones in a basic not that effective way
2 pipe system - for each fan coil unit has a return
4 pipe system - each coil has a hot and cold and a separate supply and return
Power equation
W (power in watts) = I (current in amps) x V (voltage in volts, stadndard is 120V) x PF (power factor)
Non metallic sheathed cable
two or more insulated conductors in a plastic sleeve (residential), easy to work with, not protected well
flexible armored cable
two or more insulated conductors in spiral wound steel tape
metal clad (MC) - has a separate ground wire
Delta vs. Wye connected power
Delta - has a single voltage available (phase to phase) so only 208V or 480V, 3 hot wires connected in a triangle
Wye - has two voltages available (phase to phase and phase to neutral) so 120/208V or 277/480V, has a neutral wire, connected in a Y shape
rectifier
electrical device that converts alternating current (AC) which periodically reverses direction, to direct current (DC) which flows in only one direction
inverter
electrical device that converts direct current (DC) which flows in only one direction to alternating current (AC) which periodically reverses direction
disconnects / safety switches / switch gear
first thing where power comes in bldg, a switch that can turn off other switches behind it, for emergency situations so you don’t have to touch high voltage high amp
leaves emergency power on
GFI (ground fault interrupter outlet)
receptacles that will interrupt circuits if they sense a 4 to 6 milliamp difference in current between the hot and neutral wires at the outlet
used wherever there will be water
electric meter
measure the consumption of electricity for billing purposes
master metering - one meter for the whole biilding
direct metering - a meter for each individual tenant
transformer
step down public power to a voltage usable by buildings
watts stay constant, but volts and amps change
occasionally can be used to step power up
exterior transformer pro & con
pro: no bldg space, no noise in bldg, low initial cost, easy maintenance & replacement, no interior heat generated, can use oil without having to fire rate
con: requires land & shade
below grade transformer pro & con
common in urban settings
pro: useful when little land is available, o bldg space, no noise in bldg, low initial cost, easy maintenance & replacement, no interior heat generated, can use oil without having to fire rate
con: earthwork costs
interior transformer pro & con
oil filled transformer must be located in a fire rated vault with the switchboard in an adjacent row
dry type transformers may be combined with switchboard in a main elec room or suubstation
con: requires proper ventilation for safety & heat loss, noise, heat generation
Ohm’s Law
current is directly proportional to voltage & indirectly proportional to resistance. if current increases, voltage increases
V = I x R, I = V / R, R = V / I
elec setup for shed
120V, single phase, 2 wire
elec set up for single family residential
120V/240V, single phase, 3-wire
The 240V for the high voltage equipment (AC system, electric range, electric dryer)
elec set up for a larger bldg
120V/208V, 3 phase, 4 wire
3 phases - because voltage cycles to 0 twice per second (sine wave) and you want to ensure the 0s don’t line up because that wears down your motor, req more maintenance, and more power
elec set up for a really big bldg
277V/480V, 3 phase, 4 wire
480V for motors, pumps, elevators, etc
decibels
(dB)
unit of sound pressure / intensity
0 dB = threshold of hearing
130 dB = threshold of pain
every time you double a distance there is a 6db drop
A weighted decibels
an expression of the relative loudness of sounds as perceived by the human ear
octave bands
groupings of decivels (dB) and frequency (HZ)
speed of sound
typically moves 1,128 feet per sec, about 1 ft per millisecond
(acoustic) transmission
the propagation of a sound wave through an object or medium
(acoustic) reflection
the bouncing back of the sound wave on striking a surface such as a wall, metal sheet, plywood, etc.
(acoustic) absorption
the process by which a material, structure, or object takes in sound energy when sound waves are encountered
absorption coefficient
respresented by alpha symbol
0-1, 0 means all the sound energy is absorbed, 1 means none of the sound energy is absorbed
noise reduction coefficient (NRC)
the avg of sound absorption at four frequency bands
0-1
higher means quieter, good is above .75
reverberation time
time it takes for the sound to drop by 60 dB
Decay takes longer in a larger room or less absorptive room
2 sec - concert hall (least amt of speech)
1.5 sec - opera house
1 sec - theater
.75 sec - classroom
.5 sec - small office
.25 sec - living room
transmission loss
the accumulated decrease in intensity of a waveform energy as a wave propagates outwards from a source, higher means quieter
flanking paths
“leaks” where sound can get in
ex:
through ducts
through ceiling into plenum
leaks between adjacent construction
transmission and impact loss thru partition
loss thru outlets and other openings
leaks at floor / wall intersection
impact sounds thru floor
strategies for sound reduction
massive - single layer gwb < multilayer GWB with staggered panel joints
airtight: ex. standard block wall < grout filled block wall
structurally discontinuous: ex. standard stud wall < staggered stud wall or double stud wall or resilient clip
Noise Criteria level (NC)
relative loudness of “background” noise in a space, higher means more noise
Lower than NC 30 is quiet, louder than NC 55 is loud
STC (Sound Transmission Class)
an integer rating of how well a building partition attenuates airborne sound, higher means quieter
50 STC req between multi fam
Impact Isolation Class (IIC)
measures impact sound transmissions through floor assemblies
higher means quieter
req atleast 50 between multi fam,
fix with resilient mat in the floor detail
reducing mechanical noise
Overall - the more space you can allow to mech space the better
Buy quiet equipment
Have silencer inside duct
Increase duct length
Internally lined duct - but there are air quality concerns with this
Have slower duct velocities
Smooth duct transitions rather than abrupt
skylight spacing
1.5 x ceiling height = spacing O.C.
Color Rendering Index (CRI)
a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural or standard light source, 0 - 100 with 100 being perfect
For us to see a color there has to be that color in the source light
Correlated color temperature
color that the lamp appears (warmer - cooler)
higher temperature lights are cooler, lower temperature lights are warmer
Incandescent lamp
tungsten filament placed in a sealed bulb with inert gas
Pro: high color rendition index (CRI=100), inexpensive, compact, dimmable, warm light
Con: low efficiency (lot of watts going in and less lumens going out), short life, high heat
Fluorescent lamp
a mixture of inert gas and low pressure mercury vapor. Requires a ballast which produces noise. Class A lights are quietest, Class F are loudest
Pro: high efficiency, low cost, long life, variable colors, dimmable
Con: CRI of 65-85
Metal Halide
High color temp (cooler looking), CRI of 85
Long lamp life
Used in stadiums, warehouses, car washes, etc
high pressure Sodium Lamp
CRI of 20
Often in street lighting
Long lamp life, very efficient
Light Emitting Diode (LED)
Pro - high CRI (85), produce minimal heat, low energy cost, long life span, very efficient
Con - have a hard time shedding heat, fade as they die
strategies to use daylight
Occupancy sensor
Zoning of lights - lights closest to window on one sensor, mostly off, next row in 50% on, etc
Demand response - shed lighting laid during peak energy usage times
Lamp Lumen Depreciation (LLD)
over time lamps produce less light, so you overlight at beginning, knowing that the lamps will degrade, number from 0-1, if you lose 10% of LLD you have an LLD of .9
Footcandles
the unit of illlumination, equal to the number of lumens falling on each SF of a surface
= lumens / area in sf
normal interior levels are 10-100
wet pipe sprinkler
most common, the sprinkler piping is constantly filled with water. When the temperature at the ceiling gets hot enough the glass bulb or fusible link in a sprinkler will break. Since the system is already filled with water, water is free to flow out of that sprinkler head
dry pipe sprinkler
filled with pressurized air or nitrogen instead of water to prevent frozen and burst sprinkler pipes in areas with colder temperatures, best for unconditioned space in a cold climate
pre-action sprinkler
a dry sprinkler system, water is not contained in the pipes but is held back by a pre-action valve. A voice command will then say sprinkler are about to go off in 30 second, giving the opportunity to cancel the sprinklers
deluge sprinkler
for high hazard area, when triggered, all the sprinkler heads in a zone will spray
fire extinguisher type A
water based, used for paper or wood
fire extinguisher type B
foam based, used for chemical fires
fire extinguisher type C
foam based, used for electrical
fire extinguisher type D
foam based,used for combustible metals
hydraulic elevator
powered by hydraulic jack, which are fluid-driven pistons that travel inside of a cylinder
pro: low initial cost, low maintenance cost
con: high energy demand, hydraulic fluid is an environmental hazard, slow, limited travel distance
traction elevator
utilize steel ropes or belts on a pulley system
pro: more efficient, last longer, require less maintenance, faster, smoother ride, longer travel distance
con: high initial cost, medium maintenance cost
geared elevator
traction, max rise of 150’, 5-15 stops, 500 fpm
has more torque, so often used in freight elevators
gearless elevator
traction, max rise of 2000’, 15-60 stops, 2400 fpm
machine roomless elevator
either traction or hydraulic
mac height 250’ max
500 fpm (traction), 150 fpm (hydraulic)
pro: requires less space, energy efficient, similar cost to general traction
con: difficult to implement, restricted by code, no destination dispatch system, not suitable for freight
shaft requirement for hoistway
required to have a vent that is 3.5% of hoistway or 3 sf, whichever is bigger
escalator
Slope: 30-35
Speed: 100 to 125 fpm
Clearance: 7ft req.
Capacity: 1.25 people per tread
Max rise: 20-40 ft, 60ft if supported in the middle
pipe “schedule” naming
Pipe sizes are named by wall thickness, have same diameter (ex. Schedule 40 pipe has thinner walls than schedule 80)
