Building Systems, Materials, & Assemblies Flashcards
General comfort range
69-80 degrees with a stretch of 60-85 degrees
IMC andIBS requirements for heating systems
require any space for human occupancy to be provided with an active or passive space heating system capable of maintaining a min indoor temp of 68 degrees at a point of 3’ aff on the design heating day
Effective temp
a derived value that combines the effects of air temp, humidity, and air movement
Dry bulb temp
measured with standard thermometer
Wet bulb temp
measured with sling psychrometer, a thermometer with a moist cloth around the bulb; hygrometer systems have been taking the place of sling psychrometers
Relative humidity
the ratio of the percentage of moisture in the air to the maximum amount of moisture that the air can hold at a given temp without condensing; comfortable ranges between 30% and 65%; tolerable ranges between 20% and 70%
Windchill effect
a tolerable cold temp becomes unbearable when there is wind
Air movement speeds
50 ft/min - 200 ft/min is usually not annoying
Emissivity
a measure of an object’s ability to absorb and then radiate heat
Emittance
the ratio of the radiation given by an object or material to that emitted by a black body at the same temperature
Mean radiant temp
a weighted average of the various surface temps in a room and the angle of exposure of the occupant to these surfaces, as well as of any sunlight present
Operative temp
an average of the air temp of a space and the MRT of the space
Clo
the unit to quantify the effects of clothing; one clo is equal to the thermal insulation given by the typical business suit; 0.15 clo per pound of clothing
IMC requirements for ventilation
requires every occupied space to be provided with either natural or mechanical ventilation
Natural ventilation size
area to be opened to the outdoors equal to at least 4% of the floor area being ventilated; if through another room, the area must be equal to at least 8% of the interior space
Mechanical ventilation rate
rate of supply air brought into the room or space must be approx equal to the rate or return air, or exhaust air, carried out of it; positive pressure may be needed
Comfort carts
-Show the relationships among temp, humidity, and other comfort factors
-humidity limits of 30% to 65% are preferred to be used
Psychrometric chart
-A graphical representation of the complex interactions between heat, air, and moisture
-used to calculate how much heat and moisture needs to be added or removed by an HVAC system for comfort
Enthalpy
the total amount of both sensible and latent heat in the air-moisture mixture
Enthalpy line
used to determine the total amount of heat that must be either removed or added
Heat loss calculations
Helps determine the size of the heating system for the building
Thermal conductivity, k
the rate at which heat passes through 1 SF of a 1” thickness of the material when the temp differential is 1 degree
Conductance, C
Same as Thermal conductivity, but the thickness is other than 1”
Resistance, R
the number of hours needed for 1 Btu to pay through a material of a given thickness when the temp differential is 1 degree
R = k/C
A heat loss calculation; material values given in standard reference texts and ASHRAE Handbook of Fundamentals
Overall coefficient of heat transmission, U
the value used to calculate heat loss when a building assembly uses more than one material
U= 1/sum of R values
q=UA(temp difference)
total heat loss, q, when the entire area is made of one material
Calculating total heat loss of different assemblies
all assemblies and materials must first have their heat loss calculated and then added together
deltaT or temp difference
determined by subtracting the outdoor design temp from the desired indoor temp in the winter, usually 70 deg; outdoor design temp in ASHRAE or set by municipality
Vapor barrier is placed on which side of insulation
placed on the warm side of insulation
Thermal gradient
shows variance in temp through a cross section of a construction assembly to help locate the dew-point temp
Heat loss through infiltration calculation
qv = V(1.08)deltaT
V, volumetric flow rate of air infiltration
Design equivalent temperature difference (DETD)
takes into account the air temp differences, effects of the sun, thermal mass storage effects of materials, colors of finishes exposed to the sun, and daily temp range; values published in ASHRAE tables
design cooling load factor (DCLF)
takes into account type of glazing, type of interior shading, and outdoor design temp; multiplied by the area of glazing to determine the heat gain through glazing
Sensible heat
heat that causes a change in temp of a substance but not a change of state
Latent heat
heat that causes a change of state of a substance
Heat gain through infiltration calculation
Multiply the total area by an infiltration factor
If mechanical ventilation, calculation
the volume of air being introduced to the building is multiplied by the amount of heat that must be extracted both to cool and to remove excess humidity
Energy sources
Natural gas (propane)
Oil
Electricity
Steam
Heat pumps
Natural energy sources
Natural gas
-Most efficient; clean burning; and relatively low cost
-may not be readily available, especially in rural locations
-propane: a type of gas roar can be used in areas where natural gas is not available; delivered in pressurized tanks
Oil
-Usually widely available depending on region
-cost and availability depend on world and local market conditions
-stored in or near the building
-equipment for burning requires more maintenance
Electricity
-Easy and inexpensive to install
-simple to operate
-easy to control
-flexible in zoning
-cost for use is high compared to other fuels; sometimes more charged for peak use
-on-site photovoltaics can reduce the reliance on utility supplied electricity
-ideal for radiant heating
Steam
-Not basic
-used most often on campuses and in urban locations; available from a central plant; by-product of electricity
-not usually used for direct heating; piped into building and used to heat water and drive absorption type water chillers for ac
Heat pumps
-A device that reverses the natural flow of heat travel from warm to cool; absorbs heat from a cooler location and transfer to a warmer one using principles of refrigeration
-can heat in the winter and cool in the summer
-heating efficiency decreases as outdoor temp decreses
-more effective in milder temperate climates
-solar energy system or electrical resistance heating may be used supplementarily
Natural energy sources
-Solar, PV, geothermal, wind, and tidal
-solar readily available and cost efficient
-PV harder to justify cost
Degree days
rough measure of how much heating is needed for human comfort in a particular location over the course of a year; difference between base line indoor temp of 65 degrees and average outside temp for the day
Degree days are used to determine
how much fuel is needed; daily values for the year are added to get the total number of degree days for the year
Typical fuel efficiencies
-natural gas - 70-80%
-propane - 70-90%
-no.2 oil - 65-85%
-anthracite coal - 65-75%
-electricity - 95-100%
Most common fuel to heat converters
Furnaces and boilers
How furnaces work
furnace burns fuel inside a combustion chamber, air circulated around chamber by fan, cool air returning to chamber circulated and is heated for distribution; exhausts gases
Forced air furnace, upflow
the return air is supplied at the bottom of the unit and the heated air is delivered to the bonnet above the furnace where it is distributed through ductwork
Forced air furnace, downflow
opposite operation; used in cases where ductwork is located in a basement or crawl space and the furnace is located on the first floor
Forced air furnace, horizontal
designed to be used in areas where headroom is limited, like crawl spaces
How boilers work
uses fuel to create hot water or steam; fuel is gas, electricity, oil, or steam; tubes containing water to be heated are within the combustion chamber
If primary fuel source is electricity or steam
an exhaust flue is not needed
How compressive refrigeration works
Based on the transfer of heat during the liquefaction and evaporation of refrigerant; as refrigerant as a gas is compressed it liquefies and releases latent heat as it changes state; liquid expands and vaporizes back to gas, absorbs latent heat
Fundamental component of compressive refrigeration system, compressor
receives the refrigerant as a gas and compresses it, turning it into a liquid
Fundamental component of compressive refrigeration system, condenser
the liquid flows into here and its latent heat is released; usually located on outside of building
Fundamental component of compressive refrigeration system, evaporator
refrigerant enters here and draws heat from its surroundings (air or water) and expands, becoming gas again; leaves evaporator and reenters compressor to begin again
Absorption refrigeration
-most often done with steam, also with high temp water produces by solar collectors
-less efficient than compressive refrigerants
-most often used when waste heat is available for energy input to the generator part of the system
How Evaporative cooling works
Water dropped over pads or fin tubes through which outdoor air or water is circulated; water evaporated and heat is drawn from the air of water circulating; cooled air then distributed
only works in hot-arid climates ; can be more cost effective in these climates and simpler construction and operation
ton of refrigerant or ton of cooling
a unit to describe the capacity of a refrigeration system
HVAC System, Direct Expansion Systems
-Also known as incremental unit
-simplest type of HVAC
-self-contained; passes non ducted air over an evaporator which cools the air; air discharged into room
-ventilation comes from outside
-through-wall, roof mounted, or packaged
-⅓ to 2 ton capacity for individual rooms
-capacity over 2 ton serve several rooms in one zone
-add a heating oil and DX can heat too
HVAC System, All Air Systems
-Cools or heats using only condition air
-heat transferred via supply and return ducts
-most basic is constant volume single duct; single duct common in residential and small commercial; air heated or cooled in central furnace of air conditioner and distributed via ductwork at a constant volume; 1 central thermostat; simple but cannot be zoned
variable air volume systems VAV
heated or cooled as needed in central plan and distributed at a constant temp through a single duct; each zone has a thermostat controlling a sampler that varies volume of conditioned air entering; dampers at return allow variable amount of fresh air to be introduced for ventilation and cooling when outdoor temps mean the space doesn’t;t need to be mechanically conditioned; limited in a ability to compensate for extremes; very efficient
high-velocity dual-duct system
2 parallel ducts run to each space; one with hot air and one with cool air; both stream joined in mixing box in proportion to temp; thermostat control pneumatic valves in mixing box; zones can essentially be used; ducts can be smaller to save space; inefficient because both hot and cool are supplied at all times; larger fans, more energy; noisy; high initial cost for ducts
reheat (constant volume) system
return air and outdoor air mixed; cools and dehumidifies mixture; distributed at constant volume at low temp; air reheated as needed based on the cooling load at to neat the space; reheating with heated water, or sometimes with electricity;if reheating equipment is near space its terminal reheat system; if located in ductwork of an entire zone, unit is called a zone reheat system; thermostats control valves in the water supply line and regulate temp; sometime economizer cycle is used to allow outdoor air to be used for cooling when temps are low; humidity and temp can be carefully controlled and low supply temp equates to smaller ducts and lower fan horsepower; uses more energy
multizone system
supplies air to a central mixing unit where separate heating and cooling coils produce SPE rate hot and cold airstreams; mixed with dampers controlled by zone thermostats; offer same advantage as dual-duct systems in that simultaneous cooling and heating of different zones can be accommodated; disadvantage is duct space is larger when zones are added; usually only used for medium-sized buildings or where central mixing unit can be located on each floor
HVAC System, All Water Systems
-Uses a fan coil unit in each conditioned space; fan coils connected to one or two water circuits; ventilation provided with opening through the wall at the location of the fan coil unit, from interior zone air heating or by simple infiltration
-a supply pipe and return pipe
-efficient way to transfer heat
-easily controlled; thermostat in each room regulated how much water flows through the coils
-humidity control not possible at central unit
HVAC System, Air Water Systems
-Relies on a central air system to provide humidity control and ventilation air to conditioned spaces
-majority of heating and cooling is provided by fan coil units located in each space
-often used where return air cannot be recirculated because of the potential for contamination (hospitals and labs); 100% outside air is supplied and return air is exhausted to exterior
-induction system used to supply air throughout the building under high pressure and velocity to each induction unit, where velocity and noise are attenuated before the air passes over the coils and is heated or cooled as needed; water supply system delivers heated or chilled water to the coils through either a 2 or 4 pipe system; thermostatic control is provided to each unit or group of units by regulating the amount and temp of water flowing through coils
HVAC System, Electric System
-Common method uses a grid of wires in the ceiling to provide radiant heating
electric baseboard radiators
-provides a uniform, clean, inconspicuous form of heating that can be controlled with a separate thermostat in each room
-Ductwork and piping not needed
-not usually economical except where electricity is inexpensive
-mostly used for supplemental heating in localized radiant panels or where water or air systems may need a boost in temp
Selection of Systems, profile of the building
flexibility for tenants, multiple uses or variations in heating and cooling loads
Selection of Systems, building scale
central vs individual units
Selection of Systems, control needs
sleeping rooms or units and tenants need thermostatic control
Selection of Systems, fuels available
most often which fuel system is most readily and economically available
Selection of Systems, climatic zone
wide swings in temp, humidity
Selection of Systems, flexibility
change internally by tenants and added onto in future
Selection of Systems, integration with building systems
structure and height; coordination with disciplines
Selection of Systems, economics
initial costs, long term maintenance, cost of operating the system
Selection of Systems, HVAC systems for building types
-Direct expansion: residential - single family
-constant volume single duct: auditoriums/theaters, churches, hospitals, hotels/motels, laboratories, residential-single family, shopping centers
-variable air volume: auditoriums/theaters, churches, commercial-small, labs, libraries, office buildings, shopping centers
-dual duct, high velocity: hospitals, labs
-constant volume, terminal reheat: hospitals, labs
-multizone: auditoriums/theaters, churches, commercial-small, hospitals, libraries, office buildings
-all-water system: commercial-small, residential-single family
-all-water induction: hospitals, office buildings
-closed loop heat pumps: apartments, hotels/motels
-fan coil: apartments, hospitals, hotels/motels, office buildings, schools
-electric: commercial-small, residential-single family
Exhaust systems includes
Systems designed to handle hazardous and nonhazardous exhaust and systems needed for specific equipment operations and those intended to exhaust away from sources of contamination
Energy Conservation, Mechanical System Components
Reasonable to include energy-efficient mechanical systems in an overall strategy for energy conservation and sustainability
Energy Conservation, Economizer Cycle
-Uses outdoor air when it’s cooled enough to mix with recirculated indoor air
-reduces energy needed for refrigeration and useful when outdoor temp is ~60 degrees; as temps drop less outdoor air is used to reduce the need to heat it
-a mechanical substitute for a window
Energy Conservation, Dual Condenser Cooling
-Refrigeration equipment uses 2 condensers instead of one
-when heat is needed, the heat recovery condenser is used to send waste heat to fan coil units or other devices
-when heat is not needed, heat rejection condenser sends heat to the cooling towers
-multiple chiller sizes can be used instead of one large one to make use of the most efficient size
Energy Conservation, Gas Fired Absorption Cooling
-Do not rely on electricity and ozone-depleting refrigerants; usually powered by natural gas, a more economical fuel; if steam or high temp water is available it can be used
-not as efficient as electrically driven chillers; high initial costs reject more heat to cooling towers
-may be more efficient for larger buildings where electricity costs are high and low cost heat sources for steam or industrial processed are available
-equipment may also provide hot water for heating
Energy Conservation, Solar Powered Absorption Cooling
-Absorption chillers more efficient and sustainable if powered by hot water from solar collectors
-may be less expensive than running compressive chillers with electricity, even though efficiency of solar collectors is low; efficiency can be increased by using parabolic concentrating solar collectors to provide water at a higher temp
Energy Conservation, Solar Powered Desiccant Cooling
-Desiccants to dehumidify and cool air by means of evaporative cooling; a material, either liquid or solid, that absorbs water
-air passed over desiccant mounted to a wheel rotating in the airstream; it is cooled and dehumidified; thermal energy dries out desiccant to be used again
Energy Conservation, Direct Contact Water Heaters
-Passes hot gasses directly through water to heat it; natural gas burned to provide flue gases that transfer heat to the water; heat exchanger in combustion chamber reclaims heat lost
-water is considered safe for human consumption
-up to 99% efficient if inlet water is below 59 degrees
-lower emissions of carbon monoxide and nitrous oxide
-high-cost; best used where hot water is on continuous demand (food processing, laundries, and industrial purposes)
Energy Conservation, Recuperative Gas Boilers
-Also called fuel economizer or boiler economizer
-recovers the heat in the flue gases that would normally be discharged
-Designed to cool the flue gas enough to achieve condensation so both latent and sensible heat are recovered
-reclaimed heat used to preheat the cold water entering the boiler or to preheat combustion air
-efficiency at about 95%
-Some systems reduce carbon monoxide and nitrous oxide emissions
-flue gases cool when emitted, plastic vents can be used so easy installation
Energy Conservation, Displacement Ventilation
-An air distribution system in which supply air is dispensed at floor level and rises to return air grilles in the ceiling as it warms
-because at floor level does not have to be cooled as much, more energy efficient
-typically uses high percentage of outside air
-can be used with personal control and flexible underfloor wiring
-access and space in floor; only in new construction where floor to floor height can accommodate 12” or more for ductwork
-only for space next to an exterior wall to a depth of 16’
Energy Conservation, Water Loop Heat Pumps
-Uses a series of heat pumps for different zones; all connected to the same piping system of circulating water; water loop maintain between 60-90 degrees
-Some zones are in cooling mode and simultaneously some zones are in heating mode; no additional energy has to be added when they’re balanced
-automatic valves at the cooling tower and boiler direct water as needed
-very efficient when simultaneous need for heat and cooling in different parts of the building
Energy Conservation, Thermal Energy Storage
-Uses water, ice, or rock beds to store excess heat or coolness for use at a later time
-makes it possible to manage energy needs over climatic temp swings through the day or week and allows use of less expensive off-peak energy costs to cool
Heat Transfer, Energy Recovery Ventilators (or air-to-air heat exchangers)
-reclaim waste energy from the exhaust air stream and use it to condition incoming fresh air
-most efficient in very cold, hot, or humid climates where temp differential between indoor and outdoor is high; building with continuous occupancy such as hotels and hospitals
-3 conditions to meet:
—fresh air intake must be as far away from exhaust outlet as possible to avoid sucking exhaust in
—exhaust air that contains excessive moisture, grease, or other contaminants should be separated from the heat exchanger air
—in cold winter conditions, a defroster in the device may be needed to prevent the condensate in the exhaust air from freezing
I-MC allows up to 10% of recirculated air to allow the used of energy recovery ventilators
-prohibited in hazardous exhaust systems; dust, stock, and refuse systems that convey explosive or flammable vapors; smoke control systems; commercial kitchen exhaust systems; clothes dryer exhaust systems
3 common devices to facilitate air-to-air heat exchange
—flat-plate heat recovery units: 2 ducts separated by a thin wall, one for exhaust one for inlet; can only exchange sensible heat; no humidity control
—energy transfer wheels, or enthalpy heat exchangers: transfer heat between 2 airstreams through a heat exchanger wheel; air passes through small holes in wheel that are impregnated with lithium chloride or something that absorbs moisture and transfers it to the other airstream
—heat pipe: a self-contained device that transfers sensible heat energy from hot exhaust air to cool outdoor air; the hot air passes over the heat pipe and vaporizes a refrigerant in the pipe that then moves to a section of the pipe exposed to cool incoming air; the refrigerant condenses and released heat to the incoming air, warming it; incoming and outgoing pipes must be adjacent
Heat Transfer, Water-to Water Heat Exchangers (or runaround coils)
-use water or other liquid transfer medium to exchange heat
-incoming and exhaust airstreams do not have to be adjacent
-hot exhaust air passed over coils of heat transfer fluid; fluid pumped into coils that cool incoming air passes over; winter
-cooled indoor air exhausted is used to reduce the temp of hot incoming air; summer
-common in large buildings
-eliminate the possibility incoming air can be contaminated with exhaust air
-efficiency 50-70%
Heat Transfer, Extract-Air Windows
-Uses a double-panel insulated glass unit over which another pane of glass is placed on the inside of the building
-air drawn up between interior pane and the main window unit and extracted into return air system
-warms glass in winter and cools in summer; eliminates the need for separate perimeter heating system
Heat Transfer, Ground-Coupled Heat Exchangers
-Heat or cool outside air by circulating it though pipes buried in the ground
-suitable for low-rise buildings
-long runs of pipes for efficient operation
-The energy saved by using the system must outweigh the energy needed to run the fans
-Ground-source heat pump: an alternate that takes advantage of geothermal energy
Heat Transfer, Chilled Beams
-A ceiling mounted unit that uses water to provide cooling and heating
-2 types
-multiservice chilled beam system: combines an active chilled beam system with other building services such as lighting, sprinklers, data cabling, and building management system sensors
-high initial cost
-offer significant energy savings over radiation do all-air and all-water HVAC; lower maintenance; compact; quieter
passive chilled beam system
relies on natural convection; provides only cooling; usually above a suspended ceiling; air cooled by contact with piping attached to fins and sinks back down; seerate ventilation ducts required but they can be smaller; the water temp must be a little higher than the rooms dew point to avoid condensation, therefor the central chillers can be smaller; humidity of ventilation must be done through separate equipment
Active chilled beam system
integrated with ventilation system and can heat and cool; fresh air drawn in and heated or cooled and then forced out; can handle temp control and humidity at same time
Heat Transfer, Variable Refrigerant Floor (VRF) Systems
-uses a single compressor and condenser unit located outdoors, connected to multiple evaporators located in different zones
-refrigerant supplied at each zone instead of the chilled and heated water used in typical all-water systems; each evaporator individually controlled; the amount of refrigerant supplied to each zone varies
-power consumption is reduced
-can also use heat pump tech or heat recovery to allow simultaneous heating and cooling in different zones; reduces life-cycle energy costs
-Ideal for offices, hotels, schools, multifamily residential, and Andy building with varying loads and zones; Reno work because small size of piping and compressor and evaporators; not for large open volumes
-quicker installation; quiet; flexibility in location of equipment, reduced piping, central control, monitor energy use as part of building management system
Heat Transfer, Building Automation Systems (BAS)
-a computer-based system used to monitor and control building systems
-systems controlled will vary depending on the complexity of the building and the needs of the owner; typically include HVAC, energy management, lighting, life safety, and security; may also include vertical transportation, communications, material handling, and landscape irrigation
-reduces energy costs, allows for monitoring of large complex buildings, reduces the number of personnel needed to supervise a large building, improves occupant comfort, provides detailed documentation of the performance of the subsystems
-BAS informs building systems manager if problem arises
Heat Transfer, BAS, Energy Management System (EMS)
detects environmental conditions both inside and outside the building, monitors the status of all equipment (including temp, humidity, and flow rates), and optimizes the control of the equipment (including start and stop times and operation adjustments)
Ampere
amp; A; the unit flow of electrons in a conductor equal to 6.241 x 10^18 electrons passing a given section in 1 sec
Energy
the product of power and time, also called work
Impedance
the resistance in an alternating current (AC) circuit, measured in ohms
Ohm
the unit of resistance in an electrical conduit
Power factor
the phase difference between the voltage and current in an alternating current circuit
Reactance
part of the electrical resistance in an alternating current circuit, caused by inductance and capacitance
Volt
v; unit of electromotive force or potential difference. 1 V is the amount of force or potential difference that will cause a current of 1 A to flow through a conductor whose resistance is 1 ohm
Watt
W; unit of electrical power
Basic electrical circuit
consists of a conductor, the actual flow of electrons (current), an electric potential difference to cause the electrons to move (voltage), and some type of resistance to the flow of electrons; the circuit can be interrupted with a switch
Ohm’s law for DC circuits
the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance: I=V/R
Power
the rate at which work is done or the rate at which energy is used; in electric circuits expressed as watts
DC Power
Watt is the amount of power in a circuit when V is one volt and I is one amp; P=VI
PIE
power (P) equals current (I) times electromotive force (E)(another term for voltage)
AC voltage
represented as sine wave; amplitude of waves is the voltage and distance between peaks is one cycle; frequency measured in hertz or cycles per second; frequency is 60Hz in America
the power factor can be a significant factor in calculating power in an AC circuit
Circuits with only restrictive loads
have a power factor of 1
Ohm’s law for AC circuits
I=V/Z
calculation for power in AC circuits
P=VI(pf)
Units of how energy is measured
in watt-hours (W-hr) but more commonly measured in thousands of watt-hours or kilowatt-hours (kW-hr)
To calculate energy used in a system
Multiply power by times E=Pt
2 basic types of electric circuits
—series circuit: loads (zig zag lines in diagrams) are placed in the circuit one after another; the current, I, remains constant but the voltage potential changes or drops across each load; not used in building construction
—parallel circuit: loads are placed between the same 2 points; voltage remains the same but the current is different across each load; adding up the individual currents results in a total current that is applied to the circuit as a whole
Conductor
Basic material of an electrical system
most common conductors are copper and aluminum; aluminum has to be larger but is lighter and lower installation cost in larger sizes; aluminum limited to primary circuits with careful installation
Cable
single insulated conductor, no.6 AWG or larger, or several conductors assembled into a single unit
Wire
8 American Wire Gauge and smaller
Ampacity
current carrying capacity of a conductor; depends on conductor size, the type of insulation around it, and the surrounding temp
Conduit
supports and protects wiring, serves as a system ground, and protects surrounding construction from fire if the wire overheats or shorts; usually needed in commercial or a large residential for individual conductors
How many 90 degree bends are allowed between pull boxes?
No more than 4
Underfloor raceway, underfloor ducts
steel raceways cast into concrete floor at regular intervals (4, 5, or 6 ft); feeder ducts run perpendicular and carry power and signal wiring from the main electrical closet to each distribution duct; preset inserts placed along distribution ducts at close intervals and tapped where an outlet connection is needed
Underfloor raceway, cellular metal floors
part of the structural floor; cells are closer together; alternating cells used for power, telephone, and signal cabling; cellular floors also have reset locations that can be easily tapped to install electrical outlets, telephone jacks, and computer outlets
AC, alternating current
most common for of electrical energy in buildings
DC, direct current
used for some types of elevator motors and low-voltage applications such as signal systems, controls, and similar equipment
Providing Electrical service
provided to property line; owner installed and pays for wiring, metering, transformers, and distribution beyond that point
overhead service at smaller projects connects a service cable to a weatherhead mounted at least 12’ above the ground
sometimes for larger commercial buildings its more cost effective to pay for a higher voltage for the transformer to step down rather than pay a higher charge for lower voltages
120/240 V , single phase, three-wire system
most common for residences and very small buildings
120/208 V , three phase, four-wire system
most common in larger buildings; allows for variety of electrical loads
277/480 V, three phase, four-wire system
also used in larger buildings; same as 120/208 V except voltage is higher; system can use smaller feeders, smaller conduit, and smaller switchgear; 277 V fluorescent lighting used; step-down transformers used where 120 V service is needed
2400/4160 V, three phase, four-wire system
used in very large commercial buildings and factories
Transformer
-Used to change alternating current voltages either up or down
-owner supplied the transformer unless its a residence or small building, in which case the utility company usually supplies step-down transformers to serve a small group of houses
-Rated on their capacity in units of kilovolt-empires (kVa); described by their type, phase, voltage, method of cooling, insulation, and noise level
-for cooling transformers are wither dry, oil-filled, or silicone filled
-transformers on outside wall and vented to outside
Watt-hour meter
most commons; registers the use of power over time in kilowatt-hours
Load factor
the ratio of the power used to the max power demand; low load factor is inefficient
Load control
a method used to avoid peak electricity use
Max interval demand
the average amount of energy used in a a certain time period such as 15 min or 30 min
most utility companies make charges based on this
Switchgear
-central electrical distribution center
-needed by large buildings
-switchgear consists of switches, circuit breakers, and cables or bus ducts that distribute power to other parts of the building; transformer and metering often included; equipment usually housed in separate room which may be required to have fire rated walls and doors and panic hardware
-power coming through meter and transformer split into separate circuits, each with a master switch and circuit breaker to protect the circuit from overload or short circuits; switchgear distributes power to substations
Power supplied is not always steady and regulated
individual power surge and voltage variation problems can be solved with specific pieces of equipment such as voltage regulators, surge suppressors, and filters
Power conditioning units can be used where?
in larger computer rooms or for sensitive electronic equipment
Harmonic current
voltage or current at a frequency that is a multiple of the fundamental frequency; a problem for many buildings containing computers and other electronic equipment; produced by electrical loads that are nonlinear which includes almost any load other than simple resistive loads such as incandescent lights, heaters, and motors; problems can include overheating of the neutral conductor wiring, nuisance tripping of circuit breakers, overheated transformers, and telephone interference ; solved by over sizing the neutral conductor and adding passive harmonic filters or active line conditioning that introduces the line voltage and adds and equal but out-of-phase voltage to cancel the harmonics
Secondary Distribution
-Power from main switch board distributed to individual panel boards where further split into individual branch circuits used for power, lighting, motors, and other needs
-involves the lower voltages of 120 V, 240 V, and 277 V
Each circuit is protected with what?
circuit breakers in panel board; rated for the amperage the circuit is expected to carry ranging from 15 A and 20 A for general lighting and power circuits to 100 A or more for main disconnect switches or large loads
Protection for electric circuits, grounding
provides a path for a fault; ground wire and neutral wire grounded at the building service entrance to either a grounding electrode buried in the earth or in the foundation or to a buried cold water pipe; all new construction grounded with a separate wire in addition to the hot and neutral wiring of each circuit
Protection for electric circuits, ground fault circuit interrupters (GFCIs)
devices that can detect current leaks; if detected the device disconnects the power to the circuit or appliance; can be part of a circuit breaker or installed as an outlet; required in bathrooms, garages, accessory buildings at or below grade, crawl spaces, unfinished basements, countertop receptacles in kitchens, laundry and utility rooms, and boathouses as well as outdoors and within 6’ of the outside edge of a wet bar (all in dwellings)
Protection for electric circuits, arc-fault circuit interrupter (AFCIs)
helps protect against the effects pf arc faults by recognizing characteristics that are unique to arching and by de-energizing the circuit when an arc fault is detected; sometimes required in bedroom branch circuits that serve both receptacles and lighting; NEC requires them on 15 A and 20 A branch circuits that supply outlets in family rooms, dining rooms, living rooms, libraries, dens, sunrooms, recreation rooms, closets, hallways, and similar rooms
Hardwired
electrical devices that are connected to the building circuits in junction boxes rather than plugged in
Split-wired receptacle
one outlet is always energized and the other is controlled from a wall switch
Receptacle mounting heights
typically mounted 12-18” aff; min 15” aff for forward and side reach accessibility
Most residential convenience outlet circuits are what amperage?
15 A but at least 2 20 A appliance circuits must be provided for kitchen, pantry, breakfast room, and dining room
Outlets in kitchens
not more than 24” from any point on the wall above the countertop; outlets GFCI
Two-way switch
when one switch controls a device; switch needs 2 conductors to function
Low-voltage switching
individual switches are operated on a 24 V circuit and control relays that provide the 120 V switching; more costly to install; the device can be controlled from several positions, a central control station can be set up to monitor the entire system and override control, control devices such as timers and energy management systems can be wired to override local control, and are a less expensive option when a large installation needs flexibility of control
Power line carrier system (PLC)
uses the power lines to carry control signals; no additional wiring needed
Switching required by model and energy conservation codes
individual switches rather than one switch to control all devices
Dimmers are not effective at reducing power consumption
Instead, use automatic lighting controls like a time-of-day controller
Lighting typical in commercial settings
fluorescent lights are on 277 V circuits and incandescent lights are on 120 V circuits
Emergency power supply
Required for electrical systems that relate or the safety of occupants or community needs; exit lighting, alarms, elevators, telephones, fire pumps, and medical equipment if it should have life threatening implications
What water needs to be treated for
-PH level: a measure of the relative acidity or alkalinity of water, based on scale or 0-14 with pH of 7 as neutral; below 7 is acidic, above is alkaline; rain is naturally slightly acidic
-hard water caused by calcium and magnesium salts; can cause clogged pipes and corrosion of boilers and inhibits cleaning action of detergent
-turbidity caused by suspended material in the water such as silt, clay, and organic material; not hazardous but unpleasant and treated by filtration
-color problems and odor problems cause by organic matter, inorganic salts, or dissolved gases; odor corrected with filtration through activated charcoal; color corrected though fine filtration or chlorination
-biological contamination caused by bacteria, viruses, protozoa
Pretreatment
Removes suspended matter and large particles
sedimentation uses gravity and still water and clean water on top is piped out to a secondary filtration system; can happen with or without coagulation and flocculation
Coagulation
the process of getting particles to stick together by adding alum or other chemicals
Flocculation
the step after coagulation, the mix of water and alum sent to still water, where the particles and alum form a loosely aggregated mass called floc and are heavy enough for sedimentation to take place
Filtration, slow sand filtration
allows water to seep through a bed of fine sand about 3-4’ deep; biological slime forms on sand and traps small particles and degrades organic matter; don’t require coagulation and flocculation
excellent to filter out Giardia and particulates but now for water with high turbidity
Filtration, direct
passes water under pressure through a filter medium; includes coagulation and filtration and maybe flocculation
good for elimination Giardia and most viruses
Filtration, packaged
same as direct except all elements are placed in a single unit for direct hookup to water supply
Filtration, diatomaceous earth
uses a thin layer of dia earth ⅛ - ⅕” thick placed on a septum or filter element
good for removing cysts, algae, and asbestos but not as good at removing bacteria and turbidity
Filtration, membrane
forces water at high pressure through a thin membrane that removed particles 0.2 something and larger as well as Giardia, other bacteria, some viruses, and microorganisms
Filtration, cartridge
uses self-contained units places along the water supply line to filter out particles 0.2 and larger; cartridges must be replaces when fouled but useful at faucets
Demineralization
Removed dissolved solids and the chemicals that cause hard water
Demineralization, ion exchange
used in water softeners to treat hard water and remove cadmium, chromium silver, radium, and other chemicals. Hard water piped into softener which contains zeolite; calcium or magnesium ions exchanged for sodium ions; softened must be recharged periodically; water must be pretreated
Demineralization, reverse osmosis (RO)
removes contaminants by using semipermeable membrane that allows only water to pass through and not dissolved ions; useful for removing inorganic chemicals, bacteria, and suspended particles; unit cleaned by forcing clear water through membrane which leaves contaminants in brine that must be disposed of
Demineralization, electrodialysis
places charged membranes at the inflow stream of water to attract counter ions can remove barium, cadmium, selenium, fluoride, and nitrates; expensive to buy and operate and require high water pressure and a source of direct current power
Disinfection
Destroys microorganisms that can cause humans diseases
Disinfection, chlorination
most common and kills organizations by introducing chlorine into the water stream
Disinfection, chloramine
similar to chlorination but a weaker disinfectant; add ammonia to water that contains chlorine; a secondary disinfectant to prevent bacterial regrowth in a distribution system
Disinfection, ozonation
disinfects water through the use of ozone; used as a primary disinfectant and requires secondary disinfectant for water supplies; used for treating cooling tower water to prevent Legionella pneumophila, scale, and algae
Disinfection, ultraviolet light (UV)
destroys a cell’s ability to reproduce and effective against bacteria and viruses; not effective against Giardia Or Cryptosporidium and not useful for water that contains high levels of turbidity, suspended solids, or soluble organic matter; used with a secondary disinfectant to prevent regrowth
Disinfection, nanofiltration
uses filter membranes capable or trapping particles as small as one nanometer; removes bacteria, viruses, pesticides, and organic materials; water must be forced through at high pressure
Distillation
water is boiled and then vapors are condensed to remove solids, bacteria, salts, and other material; used to treat seawater often
Aeration or oxidation
used to improve the taste and color of water; aids in the removal of iron and manganese by oxidizing them so they can be more easily removed by filtration; simple process through which as much of the water as possible is exposed to air through the use of sprays, fountains, or waterfalls; drinking water aerated in an enclosed space or tank
Depth of a well
ranges from less than 25’ (shallow well) to several hundred feet; talk to locals to take a guess at depth
Yield of a well
is the number of gallons per minute it provides; 5-10 GMP is the min required for private residence; if too low a large storage tank may need to be provided
Suction pumps
only for water tables less than 25’
Deep-well pumps
for 25-100’
Turbine pumps
used for high capacity systems with deep wells
Submersible pumps
one of the most common for moderate to deep walls serving private residences or small buildings
Pressure tanks
used to maintain a constant water pressure for use in the building to compensate for brief peak use demand that exceeds the capacity of the pump
Water mains should be adjacent to the property, but if not
the owner is often required to extend the line to the site at their own cost
All solar heating systems have what
some type of solar collector, a storage tank, associated piping to move fluids, and a backup heater
Direct system or open-loop system
water used in the building is the same after that is heated in the collar collectors; simple and highly efficient but subject to freezing; must use a draining system
indirect system or closed-loop system
a separate fluid for collection heat is transferred to the domestic hot water; easier to protect from freezing because the fluid can contain antifreeze and can operate at lower pressure; but needs a heat exchanger so loses efficiency; can be circulated actively or passively
Solar heating system, batch systems
heats water directly in a black-painted tank inside a glazed box; passive system; simple; subject to freezing and night heat loss
Solar heating systems, thermosiphon system
relies on the natural movement of heated water to circulate the water in a passive, open-loop system; simple but storage tanks must be located above the collectors and piping must be kept simple to minimize pipe friction; a variation uses a closed-loop system with antifreeze to combat freezing
Solar heating system, closed-loop active system
one of most common systems for residential and commercial; separate, nonfreezing fluid is circulated by pumps through eh collar collectors and into a heat exchanger where the domestic hot water is heater; differential controller senses when temp of the collector is lower than the stored water and turns the pumps off; flexible and provides control but suffers from some loss in efficiency because of need for heat exchanger
Solar heating system, drain-down system
a direct, active system that solves the problem of freezing by automatically draining the water form the collector when the outside temps are near freezing; water water so best fro climates with mild winters where draining is not frequent
Solar heating system, drain-back systems
indirect active system that uses water as the heat collector fluid; heated water pumped to a heat exchanger where a coil of domestic hot water is heated; when controller sense temp too low it turns off the pump and the collector water drains back into the solar storage tank
Solar heating system, phase change system
hot water systems can also take advantage of phase change materials as the collector fluid; phase change materials store large amounts of latent and sensible heat
Long span structures
Generally over 60’ in length
One-way systems
linear members span in one direction and resist loads primarily by beam action, or bending; primary members bridge the long distance and a series of secondary members span between the primary one
Two-way systems
distribute loads to supports in both directions and involve complex, 3D methods of revisiting loads
Steel girders
-Rolled steel members; used if loads are not excessive; 44” depth is largest available size to span 72’; if more moment-carrying capacity needed cover plates can be welded to top and bottom of flanges
-if longer spans are required they have to be made from individual components: most common is plate girder which is sheet steel as webs and steel bar or angles as flanges; efficient
-plate girders used as roof beams can be angled toward the middle
-plate girders usually 8’ deep or more; can be used to transfer load of one column to 2 others; stiffeners are likely required
Rigid frames
-The vertical and horizontal members and joints resist loads primarily by flexure and in which moments are transferred from beams to columns; looks like the outline of a house, 2 vertical lines connected by a gable type pitch
-if fixed connections between columns and foundation and between the 2 halves it is an indeterminate structure
-if pinned connections at the same points as above it is determinate and does not develop secondary stresses caused by temp differences
-used for industrial facilities, warehouses, manufacturing plants, and other instances where a simple rectangular open space is required
-primarily made of steel but sometimes glulam
Trusses
-Straight members that form a number of triangles, with the connections arranged so that the stresses in the members are either in compression or tension.
-efficient to span long distances cuz rely on compression and tension, not bending, and high strength to weight ratio
-relatively light, mech equip friendly, can be partially prefab, efficient use of material, probably made as deep and large to span any distance
-number of connections increases fab and erection time
-spaced 10-40’ OC with purlins spanning between and bearing on panel points (where web members intersect the top chord); decking spans between purlins
Open web steel joists and joist girders
-Prefab truss members using hot-rolled or cold-formed steel members
-3 major groups: K-series (spans up to 60’), LH-series (direct support of floors and roof decks) , and DLH-series (direct support of roof decks) (both these are long span)
-LH-series (long span joists)
—18-48” depth, span up to 96’
-DLH series (deep long span joists)
—52-72” depth, span up to 144’; depths increase in 2-4” increments
-underslung or square ends
-made with camber, the rise in the beam to compensate for deflection
-very flexible; can bear on steel beams, masonry walls, concrete walls, and joists girders
-lightweight, goes up quick and easy
-Joist girders serve as primary structure that support evenly spaced open-web joists; available in 20-120” depth and span 100’; made with steel angle sections
Vierendeel trusses
-Composed of a series of rigid rectangular frames; no triangle members so not a true truss; members must resist bending and tension and compression
-used when diagonal members are not wanted and sometimes occupies entire story height
-must be designed with bigger members and joints must resist moments; therefore often have triangular brackets
Glued-laminated beams
Much larger span than normal wood members but seldom exceeds 60’ long span
Prestressed Concrete
-Has a member that has had an internal stress applied before it is subjected to service loads; stressed by stressing high-strength steel strands in a form into which concrete is formed; when concrete cures the external stress is removed and is transferred to the concrete; helps also reduce cracking and deflection and can span longer spans with smaller sections that with reinforced cast-in-place construction
-3 most common long span sections:
—Single tees: 4, 6, or 8’ w with 8-12” thick web and 1-4’ d with spans up to 120’
—double tees: 8-10’ w with 2” flange thickness and 8-32” d; spans 60-80’; 2” thick concrete topping to cover the joints; function both as structure and decking; inexpensive to produce; quick erection; used as either horizontal or vertical members; space between can be used for mech and elec runs
—AASHTO: generally limited to highway bridges but similar rectangular beams can be precast to span long distances with lengths up to 120’
Post-tensioned concrete
-Concrete member cast with hollow sleeves embedded in it to allow a chamber for high-strength steel cables called tendons; after concrete cured tension is applied to the tendons by hydraulic jacks
-can be used in floor slabs, beams, or other sections to increase the load-carrying capacity of the member
Arches
-Depends on compression to resist loads
-internal forces makes the arch want to spread, the tendency to spread is called thrust and is inversely proportional to the rise or height of the arch: as rise increases thrust decreases
-typical range is 50-240’ for wood, 50-500’ for steel, 40-320’ for concrete
-typical depth-to-span ratios are 1:40 for wood and up to 1:100 for steel
-can be fixed or hinged; if hinged at supports it can moved slightly under loads caused by temp, soil settlement, and winds without developing high bending stresses
-arches primary structure with secondary members spanning in between to support the roofing system
Design and selection for consideration for one-way systems
-function
-cost and economy
-shipping
—Max length is 60’ for truck shipment and 80’ for railroad shipment
—max height is 14’ for truck shipment
—site limitations may also be a problem
-acoustics
—Barrel vaults, domes, and polygonal shapes can increase the noise level or produce undesirable echoes
-assembly and erection
-fire protection
—Cost and difficulty of installing fire protection covering may offset the initial cost or an otherwise efficient material
—steel vulnerable to high temps
—IBC allows A and E occupancies to be without fire protection is the roof is more than 25’ above the floor
Large span structures, two-way systems
-Distribute loads in 2 or more directions and consist of members that are all primary
-structurally more efficient than one way systems
-Most efficient if the shape is a square so loads are equally distributed
-if rectangular more load is carried in the short dimension than the long dimension, if the proportion is 2:1 nearly all load is carried in the short dimension
-offers redundancy so the failure of one connection will not cause the others to fail too
-more complicated to design and build
-nearly all of them can only be used for roof structures due to their shape, space frames are exceptions; applies only to long span systems
Space frames
-3D structural system that transfers loads through a network of members attached to each other at nodal connection points
-Very efficient because of the large number of members and they resist loads primarily in compression or tension
-redundancy is featured
-have a top chord grid and a bottom chord grid connected with diagonal bracing; the 2 grids can be identical and run in the same direction or run in different directions while still forming a regular pattern; grids can be square or triangular
-simplest form is a 2-way truss system; trusses span 2 direction and are interconnected to form a grid on square openings; diagonal members are vertical and in the plane of each truss
-more common version is the offset grid; top and bottom grids consist of identical squares but the bottom one is offset by ½ grid; connected with skewed diagonal members
-most economical depth-to-module ratio is about 0.707; the larger the size the fewer connections the less it costs
-cantilevers of 15-30% of the span are possible and desirable since less chord material is used
Domes
-One of the most efficient structural systems because the shape helps resist loads placed on it primarily through compression and tension (and shear is it’s a thin-shell structure )
-3 basic variations: frame dome, geodesic dome, and thin-shell dome
-The compression and expansion of the meridians of the domes is held in check by the hoops of the dome
Geodesic domes
-Like space frames formed in the shape of a phere
-grid is based on circle arcs and is composed of spherical polyhedrons formed of equilateral triangles
-extremely strong and still and lightweight; enclose the greatest volume with the least surface area
-can easily span 400’ or more
Thin-shell structures
-A class of form-resistant structures whose strength is a result of their ability to support loads through compression, tension, and shear in the plane of the shell because off their basic shape
-the other form resistant structure is membranes which can only support loads through tension
-most common single curved shell is the barrel vault; end frames can be added to transfer the load to the ground
-lamella roof: a structure formed by 2 intersecting grids of parallel skewed arches covering a rectangular area; very efficient
-doubly curved shells: synclastic shells (those with curves on the same side of the surface) and anticlastic shells (those with tha main curves on the opposite sides of the structure) (hyperbolic paraboloid)
-very rigid and efficient; every part of it is resisting compression, tension, and shear
Membrane structures
-Can only resist loads in tension
-must be anchored between elements that can be places in compression like the poles of a tent
-very efficient in material use; they move and change shape in response to varying loads and flutter in the wind; can restless the membrane with enticlastic shapes to counteract these problems
Air-supported structures
-Another form of the membrane structure; also called pneumatic roof
-Still only supports loads through tension but the membrane is held in place by air pressure rather than cables and compression members
-inflate the membrane
Folded plates
-Thin slabs bent to increase the load-carrying capacity
-stronger than simple horizontal flat plates because instead of having a structural depth just the thickness of the slab, the structural depth is as deep as the fold of the plate; the span is mess, only the distance from one edge of the slab to the other
-can span up to 100’ in longitudinal direction and 25-35’ between outer folds of each plate assembly
-most commonly built of concrete but can also be plywood, steel or aluminum
-Short stiffening slab usually places at both edge boundaries to compensate for the additional stress
Suspension structures
-Only resist loads by tension; the material is utilized to the fullest unit stress capability
-the amount of tensile force is inversely related to the sag of the cable; the greater the sag the less the tension on the cable; as sag increases the tensile force and amount of able cross-sectional area required decreases but the length of the cable increases
-ideal proportion is that the sage is ½ the span so that cable is at a 45 deg angle
-optimal sag for parabolic cable is 3/10 of the span
-Optimal sag for catenary curve is ⅓ of the span
-unstable in the wind and with concentrated loads or other types of changing loads
Design and selection considerations for two-way systems
-function
-cost and economy
-shipping
—less of a problem because most assembly is done on site
-acoustics
-assembly and erection
—higher erection costs due to more labor components
Preliminary sizing of structural systems
-most common method is calculate the depth-to-span ratio
-ratios for floor systems can be reduced by 15% when calculating the structural systems for roofs
Transmittance or coefficient of transmittance
the ratio of the total transmitted light to the total incident light
—clear glass has 85% transmittance
—frosted glass has 70-85% transmittance
Translucent
a material that allows the transmittance of light but not of a clear image
reflectance or reflectance coefficient
the ratio of the total reflected light to the total incident light
Candlepower
the unit of luminous intensity approximately equal to the horizontal light output from an ordinary wax candle. Called the candela
Illuminance
the density of luminous flux incident on a surface, expressed in lumens per unit area; one lumen uniformly incident on 1 SF of area produces an illuminance of 1 foot-candle (fc)
Lumen
(lm) the unit of luminous flux equal in a unit solid angle of 1 steradian from a uniform point source of 1 candlepower; on a unit sphere (1’ radius) an area of 1 SF will subtend an angle of 1 steradian; area is 4pi, a source of 1 candlepower produces 12.57 lm
Luminance
the luminous flux per unit of projected (apparent) area and unit solid angle leaving a surface, either reflected or transmitted; the SI unit is the candela over square meter (cd/m2) also called the nit; in US the unit is the footlambert (fL) where 1 fL is 1/pi candlepower per SF; it takes into account the reflectance and transmittance properties of materials and the directions in which they are viewed
Luminous intensity
the solid angular flux density in a given direction measured in candlepower or candelas
Light levels
target age range is 25-65; if 50% are older than 65 the illuminance is doubled; if 50% are younger than 25 the illuminance is halved
visual comfort probability (VCP)
used to evaluate the problem of direct glare; the percentage of normal observers who may be expected to experience visual comfort in a particular environment with a particular lighting situation
Critical zone for direct glare
in the area above 45deg angle from the light source
Reflected glare
occurs when a light source is reflected from a viewed surface into the eye
Veiling reflection
if the glare interferes with the viewing task
Contrast
-The difference in illumination level between a given point and nearby points
-brightness ratios should usually be limited to 3:1 between the task and adjacent surroundings; 5:1 between the task and more remote darker surfaces; 1:10 between the task and more remote lighter surfaces
Uniformity
Affects a person’s perception of a space as being comfortable and pleasant; complete uniformity is usually not desirable except for detail oriented tasks
4 primary types of light sources besides daylight
-incandescent lamps
-fluorescent lamps
-high-intensity discharge (HID) lamps
-light-emitting diodes
Efficacy
the ratio of luminous flux emitted to the total power input to the source and is measured in lumens per watt; measures energy efficiency of a light source
Incandescent lamps
-inexpensive, compact, easy to dim, repeatedly started, warm color rendition; light can be controlled with reflectors and lenses
-low efficacy, short lamp life, high heat output; undesirable for large energy efficient installations
tungsten halogen lamp
pretty much the same make up but there is some halogen I mixed with the inert gas; longer bulb life, low lumen depreciation over the life of the bulb, more uniform color; bulb is made from quartz and is smaller than standard; can explode so usually double walled or shielded
reflector lamps (R lamps) and parabolic aluminized reflector lamps (PAR lamps)
contain reflective coating built into the lamp; increases efficacy and allows more precise beam control; available in flood (wide) and narrow (spot) beam dispersal patterns; PAR made with heavier glass and outdoor suitable
Elliptical reflector lamps (ER lamps)
improved version of R lamps; more efficient throw of light by focusing the light beam at a point slightly in front of the lamp before it spreads out; the spread is slightly smaller than R lamp; used for down lights with deep baffles or small openings
low-voltage miniature reflector lamps (MR lamps)
small tungsten-halogen lamps that are available in a variety of wattages and beam spreads; consistent high output and 2000-3000 hr lamp life; usually whiter
Fluorescent Lamps
-Contain a mixture of an inert gas and low-pressure mercury vapor; mercury arc is formed to create ultraviolet light which strikes the phosphor-coated bulb to fluoresce and produce visible light
-high efficacy, low initial cost, long life, available in many color temps, dimmable though expensive
-larger than incandescent, more difficult to control precisely, more suitable for general illumination
-compact fluorescent lamp (CFL) are smaller and brighter; Dow lights with reflector designs can replace incandescent downlights
-fluorescent lamps are produced in tubular shapes
Fluorescent, reheat lamp
don’t carry a current unless in operation and will not begin luminescing until the cathode has reached operating temp; supplanted by rapid-start types
Fluorescent, rapid-start lamp
maintain a constant low current in the cathode that allows them to start within about 2 seconds
Fluorescent, instant-start lamp
maintain a constant voltage high enough to start the arc in the tube directly without preheating the cathode
High-Intensity Discharge Lamps
-Include mercury vapor, metal halide, and high- and low-pressure sodium
-HID lights need time to restart after shut-off; must cool first then warm up
-3 types of outer bulbs:
—clear bulbs: used when optical control is required
—phosphor-coated bulbs: used for better color renditions
—diffuse bulbs: specified in recessed downlights installed in low ceilings
mercury vapor lamp
electric arc passed through high-pressure mercury vapor which produces both ultraviolet light and visible light in mostly blue-green; phosphors can be applied to inside of lamp to produce more yellow or red light; moderately high efficacy
metal halide lamp
similar to mercury but a combo of metal halides have been added to the arc tube; provide best combo of features for many purposes: color rendering index between 60-90, high efficacy, relatively long life; color temp shifts over its life; have outer bulb
ceramic metal halide lamp (CMH lamp)
uses ceramic arc tube instead of quartz tube so lamp can burn at higher temp, improved color rendition and light control; better efficacy than old version; higher initial cost, difficult to dim, need a ballast; useful in high ceilings and retail for point source control and color rendition
high pressure sodium lamp (HPS lamp)
electric arc passed through hot sodium vapor; arc tube made of special ceramic material; high efficacy makes them one of the most efficient lamps available; extremely long life; very yellow light but color correction is available
low pressure sodium lamps (LPS lamp)
even higher efficacy but a deep yellow color; best for street lighting or where color rendition is not important
Light Emitting Diodes (LEDs)
-A semiconductor device that uses solid-state electronics to create light; basic unit is the LED package combined with other packaged into a lamp and them into a LED luminaire; solid state lighting that includes organic light-emitting diodes and polymer light-emitting diodes
-brightness, long life, lack of heat production, low power consumption; 50000-100000 hours; can be directly controlled by a digital interface; many colors
-low efficacy, high cost
