Exam 1 - HVAC Flashcards
What is the instrument that measures sound?
Decibel Meter
In order to produce a signal and be heard, a sound must be ____ dB above the current sound power level.
10 dB
“The solution to pollution is ____.”
Dilution
Odors are usually treated by adding _____ _____ into a space.
Outside Air
The most difficult odor to remove from HVAC systems is _______.
Tobacco Smoke
“____________” is a result of shutting down ventilation and preventing fresh outside air from entering a space.
Sick Building Sydnrome
VOC stands for _____.
Volatile Organic Compounds
Sick Building Syndrome affects occupants in which ways?
Occupants experience headaches, nausea, or respiratory problems attributed to stressful factors in the working environment.
Most people will report that they are comfortable in an interior building space with __ - ___ degree air temp, at a relative humidity of about ____%.
- 68 to 75 degrees Fahrenheit
- 50%
About how many times does “peak design load” occur in an HVAC system per year?
1 time. The rest of the year is at part-load, or “shoulder load”.
What is the “Comfort Region”, in regards to psychometrics?
The Comfort Region is the transparent area on a psychometric chart which illustrates what the average person would consider “comfortable”. This can be taken to court to save your ass!
Define IAQ
Indoor Air Quality relates to the air experienced by the occupants of the building.
Required CFM for a smoking room.
60 CFM
This standard sets the minimum requirements for HVAC filter systems.
ASHRAE Standard 52
Construction sites range from ____ dB to _____ dB
80 dB to 90 dB
What are the components of “comfort”?
- Scents/Odors
- Temperature/Moisture
- Air Quality
- Noise/Sound
- Light
- Air Flow/Velocity
- Activity Level
At rest metabolic rate
300 Btu/h or 100 watts per person
This component of a cooling system compresses the refrigerant in its gaseous state.
Compressor
Condenses refrigerant gas to liquid.
Condenser
A device that causes a large pressure drop as the liquid refrigerant flows through it.
Expansion Device
Where cooling happens. Converts refrigerant to gas at a much colder temperature and a lower pressure.
Evaporator Coil or Evaporator
The maximum (or worst) design conditions.
“At Design”
A rule of thumb for calculating the design load for a cooling system.
1.0 cfm/sqft
Q = ?
cfm = ?
Delta T = ?
Q = Btu/h
cfm = Cubic Feet Per Minute of Air
Delta T = Temperature difference that is driving the load
Estimate the design cooling load for a 60,000 sqft office building. The supplied air is at 55 degrees and the return air is at 80 degrees.
- Q = 1.1 x cfm x Delta T
- cfm = 60,000 x 1.0 cfm/sqft = 60,000 cfm
- Delta T = 80 - 55 = 25 degrees
- Q = 1.1 x 60,000 x 25 = 1,650,000 Btu/hr
1 ton of cooling is equal to a cooling rate of _____ Btu/hr
12,000 Btu/hr
12,000 BTUh/ton means that a 6 ton unit would have a cooling capacity of ______ BTU.
72,000 BTU
Convert 72,000 Btu/hr to Tons
(72,000 Btu/hr) x (1 ton/12,000 Btu/hr) = 6 Tons
Rule-of-thumb for cooling load and sqft of space
500 sqft/ton
Rule-of-thumb for cooling load and sqft of space for a residential space
1000 sqft/ton (provided that R-30 is in the roof and R-19 is in the walls.
At Design Temperatures
Supply Air = 55 degrees
Return Air = 80 degrees
Energy transfer through fluid motion, in both gasses and liquids.
Convection
Ex. Heat “waves” shimmering off of hot pavement
Energy transfer because of a material’s property
Conduction
Ex. Touching a hot iron or stove
Energy transfer through electromagnetic waves (Magic lol)
Radiation
Ex. Standing near a campfire
The most visible (bright or white) component of an infrared image attributes mostly to the ______ load of the photographed area.
Cooling Load
The function of Low-E Glass
Low-E glass does not re-emit the heat it absorbs.
This instrument can measure the Wet Bulb Global Temperature.
Heat Stress Meter
The higher the WGBT, the more frequently workers should take a rest.
True or False?
True, baby boy
What causes condensation?
Any surface with a temperature cooler than the dew point of the surrounding air will cause condensation to occur on that surface.
Therefore, HVAC systems “dehumidify” an area by operating a heat exchanger surface below the dewpoint of the surrounding air.
The movement of energy through the removal of or addition of moisture in the air.
“Latent Heat Transfer”
The cooling of the air, with no removal or addition of moisture in the air conditioning process.
“Sensible Cooling”
Relative humidity still changes during this process.
Ex. Chilled beam system
Cooling of the air through the EVAPORATION of water
Evaporative cooling
Ex. Humans and their nasty, sticky, sweat. MMMMM so GoOoOOD
Why insulate chilled water piping?
To prevent condensation
Define enthalpy
Enthalpy is how much energy is in the air. Temperature and moisture are included.
This refrigerant replaced R-22
R-410a
Typical car refrigerant
R-134a
Estimated temperature entering an expansion valve
105 degrees Fahrenheit
Estimated temperature leaving an expansion valve
45 degrees Fahrenheit
The “killer” of electrical components
Heat
SEER
Seasonal Energy Efficient Ration
A rating for cooling units
Ice on an evaporator coil would be a symptom of ______.
Low refrigerant
Wet Bulb Temperature measures _____, whereas Dry Bulb Temperature measures ______.
- Humidity
- Regular temperature
The 0th Law of Thermodynamics
“There is no temperature change without the exchange of energy.”
A WBGT of 82 or greater would not be good for high activity levels.
True or false
True
The curve on the Psychometric Chart is known as the _________.
Saturation Line
Characteristics of Low-E Glass
- Prevents heat/light transfer
2. Non-reflective
A net-zero building, in theory, would ______.
Use as much energy as it creates
There are ____ branch circuits on a line diagram
0
A line diagram represents ______.
The distribution on power throughout a building
IPD
Integrated Project Delivery
This type of contract requires that every party signs, a split contingency between all parties, and a joint sharing of risks and rewards.
IPD
Just-In-Time delivery is a characteristic of CPM
True or False
False.
Just-In-Time delivery is an element of LPS
CPM vs LPS
CPM
- Detailed planning
- High resource utilization
- Schedule is forced onto people
LPS
- Plan incrementally
- Daily adjustments
- Journey men know duration of activities
- Daily Huddles
- Trust
- JIT Delivery
The number of skilled laborers is in a(n) ______.
Decline
This affects self-perform the most.
The two acronyms addressing methods of labor risk management are _____ and ______.
- TIMMES (Resources)
- DOWNTIME (Waste)
An example of modular construction could be _____.
The recently built Chinese hospital.
Data centers.
