HVAC Flashcards
What does HVAC stand for?
Heating
Ventilation
Air Conditioning
(Also the company on the thermostat)
What type of heat is the dry bulb temperature?
Sensible Heat
(Does not include humidity/moisture)
What type of heat is the wet bulb temperature?
Latent Heat
(Factors the effects of water in the air into sensible heat - effects relative humidity)
Define condensation
Condensation the evaporation of water vaper to a liquid (on a cold surface)
The more humidity the more condensation
What is the difference between air-conditioning and conditioned air?
Air-conditioning is cold air
Conditioned air is the action of mechanically manipulating air or our inside environment
What is IAQ
Internal Air Quality?
What is the equivalent to “one ton of cooling?”
12,000 BTUs
What is ASHRAE?
The American Society of Heating Refrigerating and Air conditioning Engineers?
Name the 6 HVAC goals
- Control (DB) temperature
- Provide fresh air (I.e bring in fresh outdoor air to mix with return air - why?)
- Provide circulating air
- Exhaust odors irritants
- Provide clean air (i.e. filter the air)
- Raise or lower humidity
What area is the most difficult to make occupants comfortable?
Meeting Spaces
- Better to keep it cold so people are awake
What are the 6 things to consider in terms of thermal comfort influences
- Room air temperature
- Room air movement
- Relative humidity of room air or “wet bulb” temperature
- Activity level in the room
- Clothing worn by room occupants
- Temperature of the room surfaces
What must you always consider for gym rooms in terms of room comfortability?
Always dehumidify
Describe Supply, Return and Exhaust in terms of room conditioning
Supply: New conditioned air into a space
Return: Returning back air or reconditioning (reheated/cooled)
Exhaust: Expel from the building
What are the differences between Centralized and Decentralized systems
Decentralized:
-(Single Source equipment) itself provides heating/cooling
-Not linked into anything
-Greater capacity
Centralized:
-Central source for both heating and cooling then it is distributed throughout
- One unit
- Half inside, half outside
What is a heat pump?
An apparatus or heating or cooling by transferring heat by mechanical means
- Very efficient and even more so at lower tempest
- Does use electricity
Describe what a Packaged Terminal Air conditioning Unit is
Also know as “through the wall units”
Most commonly used design as a heat pump to deliver both heating and cooling by reversing the flow of refrigerant
What is another name for a decentralized “packaged unit”?
Dx Unit or Direct expansion unit
What are the five components of a Centralized cooling and heating system?
Air Handling Unit/AHU, Fan Coil, Chiller, Boiler, Cooling Tower
What are the three medium types of centralized systems?
- Forced Air: residential
- Steam: heating only (radiators) and rare for use in hospitality(NYC,Toronto, Boston)
- Water Distribution (Secondary risers) for heating and cooling
Define Ductwork
Supply and return air ducts (typically metallic)
Explain the fan coil choice between a 2 pipe vs 4 pipe
2 pipe: Is cheaper but more limited, either only heating or only cooling, during the different seasons it has a more difficult transition between heat/cool
(Have the option to install supplemental electric heat)
4 pipe: Higher installation costs but also more flexibility during transitional periods
When you have a fan coil unit do you need ductwork?
No, a fan coil unit can be for heating, cooling or both
What are Dampers used for?
Blocks the airflow (The shudders on a Fan-coil unit)
In a Refrigeration or Vapor Compression Cycle, What does the evaporator do compared to the condenser?
The Evaporator removes heat (Makes the air colder)
The Condenser rejects heat (Sends hot air out)
Name the Four Components of Refrigeration
- Expansion value (control flow of refrigerant)
- Evaporator (liquid to vapor - super cools)
- Compressor (vapor compressed to hot, hight pressure gas)
- Condenser (vapor to liquid, hot gas cooled- condenses into liquid state_
Describe the Technicals of the Expansion Valve in the Vapor compression Cycle
The expansion value helps regulate and control the flow of the refrigerant into the evaporator
Describe the technicals of the Evaporator in the Vapor compression Cycle
Refrigerant expands and evaporates filling the space.
Refrigerant then gets very cold
Refrigerant absorb heat from space (air or water)
The refrigerant gets warmer and returns to the compressor
Describe the technicals of the Compressor in the Vapor compression Cycle
Refrigerant gas is compressed into a hot, high-pressure gas ~125F
Describe the technicals of the Condenser in the Vapor compression Cycle
Compressed gas is cooled in condenser by water or an air fan
As it cools it condenses to a liquid state
Refrigerant is now warm, high pressure liquid (~110F)
Describe it CFC: Chlorofluorocarbons (Freon)
An old type of refrigerant
Also referred to as R-11 and R-12
Very bad for Ozone :( (100% damaging chemicals)
Montreal accords. Can no longer be produced. Phased out of usage in new equipment (still being used)
Describe it HCFCs: Hyrdrochlorofluorocarbons
An old type of refrigerant
Also called R-22
Not great for Ozone (5% damaging chemicals)
Has been phased out since 2020
Describe it HFCs: Hydrofluorocarbons
No ozone impact refrigerant :)
