HVAC System Flashcards
(50 cards)
1
Q
HVAC?
A
heating ventilation air conditioning
2
Q
what are hvac designed for
A
- thermal conditions
- adequate amount of outdoor air
3
Q
what does a hvac system consist of
A
- controls
- min of one fan to move air
- provision for introducing outdoor air
- filter
- coil for heat and cooling air
- distribution system
4
Q
why is the location of air intakes important
A
- because of the potential to permit contaminates from the area
- usually 1/3 up building
- usually found next to loading docks or on roofs near exhausts
5
Q
what is the mixing plenum
A
- it is where return and outdoor air mix
- since rain and snow can be sucked in there should be floor drain
- if drain is connected to sewer line must have water trap
5
Q
what is a outdoor air damper?
A
opens and closes to control air volume passing through inlet
6
Q
what do air filters do?
A
they deliver clean air
6
Q
what do the coils in the hvac system do
A
either cool or heat air coming in
7
Q
what is the purpose of cooling coils
A
- cool air
- dehumidify air as water condenses
8
Q
what is purpose of heating coils
A
- heat the air
- provide thermal comfort
9
Q
where must coils be?
A
- accessible
- clean
- have sufficient capacity to give thermal comfort
- located centrally throughout building
10
Q
what are condensate drain pans for?
A
- collect moisture under cooling coils
- must be properly sloped towards the drain line
- should be kept clean
11
Q
what is the supply air fans
A
the driving force to distribute air into building
12
Q
A
13
Q
return-air fan, what do, what is?
A
- draws air out of building and deliver it to air-handling unit and exhausted outside
- relationship to air supply is important as resulting pressure can introduce air into air-handling unit
14
Q
boiler?
A
- generates heated water for thermal conditioning and hot-water needs
- fossil fuels or electric
- generate combustion products that may become indoor contaminants
15
Q
chilllers
A
- provide chilled water to meet cooling loads
- required for thermal comfortable conditions
16
Q
hvac system produce what?
A
- heating
- cooling
- heat transfer fluids
- control delivery to a space to maintain stable condition
17
Q
heating and cooling produced by what
A
- refrigeration devices
- furnaces
- boilers
18
Q
movement of heat transfer fluids are preformed by what?
A
- ductwork
- grillers
- diffusers for air
- pumps
- piping system for water
19
Q
name a heating and cooling control device
A
space thermostat
20
Q
heating and cooling system, explain them
A
- very temp of air supply with a constant flow
- vary flow of air supply with constant temp
- vary flow and temp of air supply
21
Q
what is a zone?
A
- one area that is controlled by a single thermostat
22
Q
single zone system
A
house with furnace controlled by a single thermostat
23
two zone system
house with two furnaces each controlled by a separate thermostat
24
two types of hvac controls, which is better
- manual
- automatic
- automatic controls system more precisely and reliably for comfort, safety, and efficiency
25
the control systmes control?
- temp sensor
- pressure sensor
- flow rate sensor
- humidity sensor
- speed sensor
- time with clock sensor
26
what are basic control devices?
- sensor
- controllers
- actuators
27
sensors?
- measure and monitor variables
- signals are input into controller
28
controller?
- provide decision for function of control system
- determines if signal is sent or not
29
actuators?
provides physical control of equipment by valves or dampers
30
thermostats?
sense and respond to temp
- signals sensors and controller
31
humidistats?
sense and respond to humidity
- either relative or absolute
32
constant temp variable volume?
- used for zone control
- simple residential system, maintains the temp set on thermostat
- turns of when the temp is achieved
33
single zone constant air volume
- simple system used in commercial building
- fans run constantly and provide ventilation
- air is supplied at a constant rate, to achieve the desired temp
34
cooling coil uses what to cool?
- refrigerant
- cold water
35
how does heat get produced by hvac system?
- furnace and space heater heat air
- fuels burnt to heat water or produce steam to heat air
- electric heat up coil to heat air
- boilers heat by hot water or steam
36
air-handling system components
- fan sections,
- cooling section
- heating section
- humidification section
- filter section
- air mixing section
- discharge air plenum
- other components
37
what is contaminates are in outdoor air?
- gas, liquid, solid particles
- bacteria
- viruses
38
fans in hvac system
moves air in the system either ventilate heat or cool
- all have rotating impeller blades, increases kinetic energy of air
- increase of energy is converted into pressure
39
ductwork includes
- supply duct
- return duct
- outside air
- relief air
- exhaust air ducts
40
ducts made from what material?
- galvanized steel
- aluminum
- stainless steel
41
what shapes can ducts be?
- rectangular
- round or flat oval
42
how does insulation in a duct work?
- applied to interior of duct (rectangle)
- applied external as fiberglass or blanket (round)
- external more expensive
- for thermal and acoustic
43
rectangular duct used for what?
- used for low-velocity applications
44
round or flat oval used for what?
- medium high velocity
45
what do air devices do?
supply and remove air from building
46
name air devices?
- diffusers
- grilles
- registers
47
what are diffusers for?
- to get rid of any drafts areas creating hot or cold spots
- it controls air quantity and direction
48
what is the coanda effect?
- allows air to fall gradually and mix with room air ver large area
- without this the chilled air will fall straight to the ground creating a cold spot
- this is called dumping creating uncomfortable draft
