Final Flashcards
What the formula to convert watts to amps?
Amps = Watts/(1.73 x Volts x PF)
PF = power factor
1 watt is how many BTUs?
1 watt = 3.41 BTUs
1 ton of AC is how many BTUs?
1 ton of AC = 12,000 BTUs
Formula for heat gain through a window in BTUs
BTU = (temp difference) x (U-value) x (SF of exterior surface area)
How do you request power for building from utility company?
Must write a “Load Letter” which summarized electrical demand.
Why do you have to ground?
So you don’t get shocked by stray currents
How do you ground?
Wires run to a grounding rod, which is embedded in the earth. Alternatively, you can attach to copper pipes or structure
What does GFCI stand for?
Ground Fault Current Intercepter
What does a GFCI outlet do?
A gfci outlet measures current and shuts off outlet if abnormal current flow occurs.
Where are GFCI outlets used?
Typically are used in any environment that might have water.
For an outlet that has three slots, what do each of them do?
one fin is the “hot” line, the other fin is a neutral, and one is a ground
How does a wires gauge relate to maximum current?
the larger the wire gauge, the higher the max current (amps) can be
What is electrical diversity?
the reduction in the calculated electrical load to account for non-simultaneous requirements
Why is AC used over DC?
It’s a cheaper method for transmitting large amount of wattage, low amps- high watts, power can be transformed between voltages as needed
What is three-phase power?
electricity flow that has three sine waves of current offset by 120 degrees so there is no point at which there is no power.
How can you tell if you have three phase power?
There will be three wires coming into the electrical panel
What phase of power do most residential homes have?
single-phase
What is a demand charge for electricity?
an additional fee for peak 15 min KW usage in any one month, used to pay for total capacity required by a power plant
What is load shedding?
A method for reducing the electrical demand lad,ad thus, the peak KW usage. Non critical devices are shut down when not in use. Tied to building management systems
List common wires systems and explain what they are
- BX - wires with armored cable
- greenfield - flexible armored cable (no wires)
- conduit - pipe to carry wires, used for security and grounding
- EMT - thin walled conduit
How are wires pulled through conduits or tubes?
Using wire fish tape
How many spares should be on a panel board?
about 25%
why does each floor have it’s own panel?
panels should be close to the loads, and there are voltage drops for long runs of wire.
What is a circuit breaker and where are they located?
a device on a circuit that shuts off the circuit if there is a surge in current to protect the devices connected. They are located within the electrical panels
are is the watt load balanced in the panel?
the watt load is balanced over the three phases of power as best as possible
what is a bus duct?
A duct to run wires to each floor of a building from the main distribution panel
what is daisy chaining?
having multiple outlets on a single circuit
Name three self-contained power systems
- generator
- UPS (uninterrupted power supply)
- Cogeneration
what is a generator?
a device that powers a building using some sort of fuel (oil or nat. gas) when main electric is lost. Takes 10-12 seconds to start
what is UPS (uninterrupted power supply)?
a battery system used to bridge any power loss, typically used in computer rooms, can only last for 10-20 minutes
what is cogeneration?
supplemental power generated from surplus heat
What are some methods to test the electrical systems?
test amperage, test voltage, test resistance (megger meter), test heat (thermal imaging)
what is the lighting unit of measurement?
foot-candles or flux
list 4 type of light bulbs
- incandescent - very inefficient
- Flourescent - more efficient, but causes ballast heat output
- LED
- metal halide - has color problems
list some methods to reduce energy usage for lighting
- occupancy sensors
- time clocks
- day light sensors
- use of more day light
- more efficient bulbs
name the NYC local law dealing with energy consumption benchmarking
LL 133
What does BTU stand for and what does it mean?
British thermal unit; a measurement that is used to describe heat gain/loss
What is the historical meaning of BTU?
the amount of heat required to raise one pound of water 1 deg F
list some sources of heat in a space
solar radiation, people, lighting, computers, equipment, conductive heat gains, air infiltration
what load is the AC designed for?
peak hour load
What’s the formula for solar load through a wall?
BTU = peak hour solar load x exposed surface area of wall
what’s the formula for BTU’s for temp difference through glass?
BTU = (temp difference) x U-value x area of glass
What is the U-value?
heat transfer coefficent; measure of heat loss through a building’s element (wall). High U = poor thermal performance. Low U = good thermal performance
how does the R value relate to the U value?
R-value = 1/(U-value)
What is NYC LL 32?
law implemented in 2020 to increase the thermal efficiency of buildings by 8% today and then 13% by 2030.
What is ASHRAE?
American Society of Heating, Refrigerating and Air Conditioning Engineers; prof. organization that sets HVAC standards
Is an HVAC system designed for the worst case scenario?
no, peak conditions only happen one or two times a year and would significantly increase the size/cost of a system if designed for it.
List six air conditioning system types
chilled water, condenser water, air cooled, ice storage, geothermal, co-generation
what is the second law of thermodynamics and how does it relate to AC systems?
2nd law states heat will flow from a hot surface to a cooler surface and this principle is used to cool refridgerant/coolant/water in an AC system
what is commonly used to remove heat from AC systems?
water
What is a PTAC system?
a packaged terminal air conditioning system
How does a home AC unit work?
air is cooled through evaporator, then refrigerant is compressed by compressor, then is cooled some in the condenser, then travels back to evaporator
How does a chilled water system work?
system has two loops: a chilled water loop and a condenser water loop. Chiller cools water, which cools building on chilled water loop. Heat from the chiller is taken away by the condenser loop and temps are reduced in the cooling tower
what is a direct expansion AC system?
evaporator is in direct contact with the air stream cooling coil (the evaporator)
how does a condenser water system with DX units work?
each floor has own DX unit to cool, condenser water runs through each unit and is cooled in a cooling tower
what are some benefits of a condenser water system with DX units?
less duct work, no operating engineer required, less penetrations, better control of space, easier to maintain, redundant equipment
why does condenser water that runs through a cooling tower have to be treated?
it is an open sytem and if untreated can cause legionnaires disease, clog pipes, corrode pipes, and evaporate
what type of maintenance is done to a cooling tower?
water chemically treated for corrosion inhibitors and biocides, water is tested 3 days per week, samples are taken to determine condition of pipes, systems are “bled” to revitalize water
what is ice cooling refrigeration?
ice is stored in tanks then warm is blown over to cool it
how does a geothermal system work?
compressor has a ground loop that can heat or cool refrigerant depending on if its a heating or cooling system
Why is a variable air volume system preferred over a constant volume system?
VAV is more energy efficient
How does a constant air volume system work?
air flows at a constant volume and the temperature is controlled by changing the temperature of the blown air
How does a variable air volume system work?
the blown air temperature is held constant and the room temps are adjusted by varying the airflow
how is airflow measured?
cubic feet per minute (CFM)
formula for calculating required airflow through duct?
CFM = BTU/[(Troom - Tduct)x1.08]
How is air returned in a building?
either through a return duct or the plenum space
how do you control temperature in a building?
a thermostat
Whats a variable frequency drive?
system that allows air flow to be adjusted to meet demand if lower than system capacity (i.e. reduce airflow to 15000 cfm from 20000 cfm)
how is the air delivered in an hvac system?
duct work
what things are considered when designing duct work?
cfm needed, velocity of airflow (for noise), size restrictions. insulation
Why do you need to insulate ducts?
keep temperature stable, eliminate condensation, reduce noise
what is air balancing?
a check to make sure the actual airflow is the same as the designed airflow
Why does a building need to be ventilated?
to replace oxygen, dilute CO2, dilute odors, dilute any chemicals in furniture or finishes
what can be done to reduce noise from an AC system (or any other system)?
use a concrete pad and spring isolators
what are some common heating systems?
boilers, warm air, heat pumps, solar cells, geothermal, co-generation
what are some ways to reduce HVAC size?
use diversity factor, do a thermal audit of building for bridging, reduce lighting loads, control hvac system with a bms, use outside air to max advantage, review building orientation (during design)
whats the typical reduction in efficiency of mechanical equipment after 1 year?
16%… needs maintenance
where was the midtown reservoir and what fed it?
located in today’s Bryant park and fed by water from Croton reservoir
what systems in a building need water?
domestic water line, sanitary lines, drainage, vent pipes, sprinkler, HVAC system, standpipe
how does a water tank work?
water is pumped up to tank, then gravity creates water pressure that feeds water to rest of building. made from cedar planks and steel hoops
what’s one common pollutant in water lines that causes problems?
Lead
what was the connection method for old cast iron pipes?
bell and spigot connection… oakum-hemp fibers expand when wet, lead used to seal joint
what replaced cast iron for waste pipes and what are the benefits?
ductile iron; made from recycled scrap iron and steel, oxide layer creates corrosion resistant product
what replaced the bell and spigot connection and how does it work?
no-hub connection; pipes connected by rubber sleeve and clamping device
how are pipes supported?
by support hangers through floor penetrations
what must you do for any floor penetration?
must be fire stopped
what are clean out plugs for?
to be able to remove any obstructions in the pipe, 1 per 50 ft
what is a sump pump?
a pump located below the grade of a waste line that can pump out waste at a higher elevation
what’s a wet column?
a column that has pipes located right next to it; used to reduce openings in rentable areas)
what’s a combined sewer?
building waste lines and street run-offs run to same combined sewer line
list some stats about the NYC sanitary system
14 wastewaster treatment plants, 150000 catch basins, 6000 miles of sewer
how is flow controlled in a combined sewer system?
inflatable dams
what’s a detention basin?
a device or tank that collects water that is released after peak run-off from a storm
what are valves used for?
to modulate flow, stop leaks or breaks in pipe, modulate pressure, restrict back-flow
list 4 types of valves and describe them
gate valve - can get stuck, but will not cause water hammer
globe valve - better for partial flow, less likely to get stuck
check valve - for flow in one direction
angle valve - space restriction and 90 deg flow
what is a vent stack?
a vent pipe that helps dilute gases, balances the air pressure in branches, and prevent siphoning
what is the general supply water pressure?
45 psi
how is water supplied to a building
delivered from a main through a back-flow valve, then pumped up to the floors
why is copper used for water supply?
it’s thinner than normal pipe, smooth, corrosive resistance, bio safe, easy to put together, does not melt
what are two considerations you must have for copper pipe?
cannot touch other types of metal, needs to be insulated
how is copper pipe connected?
brazing
What are some LEED rules for water?
potable water to be used more efficiently, recapture gray water for other uses, keep storm water on site, retain water through green roofs
what is a pipe trap?
a device that provides a water seal to prevent odors and gases from entering building
what is a trap primer?
a device that keeps water in a trap when evaporation occurs
What’s a FOG interceptor?
a device that captures fat, oil and grease in waste water before it enters sewer
what are some hot water systems?
hot water tanks, boilers, heat exchanger using steam, instant hot water heater
at what height building are sprinklers required?
100 ft
what is a siamese connection?
exterior building connection for fire department that is connected to other pipe in building
what do green, red, and yellow mean for a siamese connection?
(1) Green-Connects to building’s sprinkler system
(2) Red-Connects to building stand-pipe system
(3) Yellow-Connects to sprinkler and stand-pipe
what’s a stand-pipe?
a water pipe in building used for fire suppression
how does a sprinkler head work?
a link or bulb keeps the sprinkler sealed and if the link is melted, then the sprinkler head is open
what’s a victaulic fitting?
a pipe connection that is pressure rated
how are the sprinkler supply pipes supported?
kindorf and pipe-hangers
what are the 4 main types of sprinkler systems?
wet pipe, dry pipe, pre-action, chemical
how does a wet pipe sprinkler system work?
water is in system all the time and releases when link head melts
how does a dry pipe sprinkler system work?
pipe is empty and pressurized, when link melts negative pressure opens valve to deliver water
how does a pre-action sprinkler system work?
can be a wet or dry system, but also has a fire sensor that will send signal to valve and open it if activated. water will not flow unless links also melt
how does a chemical sprinkler system work?
same as pre-action system, but connected to tanks with chemical fire suppressant instead of water
what must a sprinkler system plan show?
location and size of water supply, location of sprinkler heads, hydraulic calcs, hazard category, riser diagram
what are the three hazard levels for fire?
light (offices) , ordinary (retail) , high (flammable storage)
list 4 fire extinguisher types
water - for solids
foam - for solids and flammable liquids
dry power - for everything expect cooking oils
CO2 - for cooking oils and electrical fires
what are some key factors when designing elevators?
waiting times, safe ride, leveling and landing, accel and deccel
what’s a hoistway?
space where the elevator actually travels
what is travel?
distance between the floors that an elevator has to travel
what’s a pit?
space below elevator at the bottom floor for maintenance and spacing
what’s a landing?
where you enter and exit the elevator
what’s an elevator opening?
where the shaft openings are for doors
what’s a safety plunger?
hydraulic stop as a secondary emergency stop
what’s an elevator machine room?
room for all mechanical equipment
what’s a rail for an elevator?
steel rails that guide elevator in shaft
what’s the maximum span for rails?
14 ft, helps decrease vibrations
what components are not allowed in elevator shafts or rooms?
no pipes, ducts or risers in machine rooms or hoistway unless for elevator
what are the code requirements for sprinklers in machine rooms?
machine rooms must have sprinklers, power must turn off before activation and typically uses preaction system
what happens to an elevator in an emergency?
all elevators drop to lobby and can only be operated by firefighters; typically tied to emergency power
What is a hydraulic elevator?
an elevator moved by a hydraulic rod that lifts and lowers the car
what are the pros of using a hydraulic elevator?
absence of cables, motors,counterweights, etc. makes hyhdraulic elevators less expensive than traction; no penthouse required for machine room; no load limit capacity; hoightway is typically smaller than a traction elevator hoistway
what are some cons of hydraulic elevator?
low speed; limited height (tops out around 65 ft); potential for oil leakage, greater operated expense
What are two types of hydraulic elevators and describe them?
holed - cylinder in located in hole in ground
hole-less - cylinders above ground on each side of elevator car
What’s a freight elevator?
an elevator with considerably larger carrying capacity to carry freight
Why do freight doors open vertically?
to protect the doors from being damaged
What is a traction elevator?
an elevator that is moved by a motor with cables on a sheave. load is balanced with counterweight
what kind of safety is on a traction elevator?
rail brakes, governor, buffer, redundancy with number of cables
what’s a typical elevator counterweight weight?
= to weight of empty car + 40% of rated live load
what are compensation cables for?
to balance the cable loads on each side of the elevator sheave
how many cables are required for traction elevator?
one, but more are added for redundancy or additional traction
what does a governor do?
limits the speed of an elevator
what are elevator guide rollers?
wheels to keep elevator car on rails
how does a governor work?
flyweight extends and catches a ratchet when speed is exceeded
what do door monitors do?
make sure elevator doors are closed before car moves
what’s the double door interface?
makes sure lobby doors and car doors open and close at the same time
what are the two types of traction elevator motors?
geared - which is an indirect drive and used for low speeds
gearless - direct drive, used for high speeds, has less maintenance
what does a counterweight do?
adds traction at the sheave, balances weight and reduced size of traction motor and thus electrical usage
what are some new technologies in elevators?
elimination of machine rooms; elimination of DC motor (can use ac); call buttons via floor, replace cables with lightweight carbon fiber belts; regenerative drive motors
what are some pros and cons of machine room less elevators?
compact, efficient, smooth, quick install
currently only allowed by variance in NY and NJ, no standard size
what’s the elevator install process?
- shafts for elevators have to be completed
- inserts installed for rails
- temp power provided
- water tight shaft area
what’s the relation between elevators and TCOs?
a TCO cannot be obtained until elevators are approved by DoB
what’s the industry benchmark for “average interval”?
Average Interval” is the average period of time, in seconds, between elevators leaving the main lobby.
and 30 seconds
what are some criteria you have to consider for interior construction?
appearance, durability, maintenance, acoustics, cost, fire/smoke, sustainability
what are some characteristics that make a product sustainable?
made of recycled material, lasts a long time, low carbon footprint, does not produce any chemicals
what does the Underwriters Laboratory (UL) do?
tests products that are considered sustainable
list factors to consider for durability and maintenance
level of wear and tear, how often maintenance is needed, cost of maintenance, useful life, access
what acoustical factors should you consider?
noise reduction coefficient rating, equipment to have isolators, privacy and noise reduction for offices/gyms/classrooms
list some cost considerations
first cost (material and install), maintenance, life, life cycle cost (NPV)
how do you calculate life cycle costs?
by calculating net present value of all of the cost components (initial cost, annual maintenance, service life, salvage value, replacement cost)
What is value engineering?
process for reducing the cost of a project by eliminating or reducing costs that will not impact the project
what are some ways value engineering can reduce costs?
replace design with cheaper materials, replace equipment with less maintenance or better service life pre-purchase items in high inflation environment,
list common interior items for VE consideration
- carpet
- hung ceiling vs hard ceiling
- glass partitions vs drywall
- paint vs vinyl wall finishing
- standard vs exotic light fixtures
- ceramic tile vs stone floors
- number of data outlets
- hollow vs solid doors
what fire/smoke factors must you consider?
- separation between various tenants (1 hr and 2 hr for assembly spaces and shaft walls)
- flame spread- materials must be tested for spread
- smoke density - materials must be tested for smoke spread
what is a material’s flame spread?
measure of a material’s ability to be fuel for a fire
what is a material’s smoke density?
the amount of smoke a material produces under fire conditions
why do floors have to be level?
tripping hazard and high points will wear quicker than rest of floor
what’s one type of floor leveling system?
pin form laying system
what is a carpet base or baseboard for?
protecting the walls and covering up flooring seams
what’s a computer raised floor and?
a raised floor used in computer rooms to increase air flow, hide wires, and ground for stray currents
whats a terrazzo floor?
a floor made from stone chips and epoxy that is ground smooth
list common types of ceilings
hung ceiling, hard ceiling, metal, wood
list common partition types
dry wall, wood, glass, wodd and glass
parts of an interior partition wall?
studs, top track and bottom track
what are studs spaced at c/c?
16 in
how are doors hung on a frame?
hinges
whats the difference between a lock/latch set?
a lock set has a lock in the door handle and a latch set has just a handle and separate lock
what is a door frame?
frame that structurally supports a door
list common types of wall finishes
paint, wall coverings, stone, special paint, wood paneling
list cable requirements
6E, if run in ceiling must be plenum rated, each jack requires cable, cable lengths have to be checked, runs must be managed
how are cable runs managed?
with o-rings, j-hooks, and cable trays
what does a plenum rated cable mean?
it’s teflon coated
what are some coordination considerations
structure, lights, ducts, pipes, sprinklers
what is required to occupy a space?
a TCO or CO
what’s the metabolic gain (in BTUs) per person per hour?
450 BTU/hr
