Hvac Systems

Front 1

What is the most efficient of all fossil fuels?
a. electricity
b. steam
c. natural gas
d. propane

Back 1

c. natural gas

Front 2

what fossil fuel has a heating value of 1,050 BTU per cubic foot?
a. oil
b. propane
c. steam
d. natural gas

Back 2

d. natural gas

Front 3

what fossil fuel is a likely good choice for a remote area?
a. propane
b. oil
c. natural gas
d. solar

Back 3

a. propane

Front 4

the disadvantage to propane is
a. it smells
b. it requires more expensive equipment to burn it
c. it requires a storage tank
d. it only has a heating value of 2,500 BTU per cubic foot

Back 4

c. it requires a storage tank

Front 5

which of the following is not true of oil as an energy source?
a. widely used in some parts of the country
b. must be stored far away from where it is used.
c. equipment to burn it requires more maintenance than gas fired boilers.
d. it is produced in 6 grades: 1, 2, 4, 5 light, 5 heavy, 6

Back 5

b. must be stored far away from where it is used.

Front 6

The most common grade of oil used in residential & light commercial is
a. residential
b. 5 light
c. 3
d. 2

Back 6

d. 2

Front 7

What are the advantages of electricity as a fuel source?

Back 7

easy to install
low installation costs
simple to operate
simple to control
flexible zoning
doesn't require storage facilities
doesn't require flues or air supply

Front 8

Electricity has an equivalent heating value of:

Back 8

3413 BTU/KW

Front 9

What are the disadvantages of electricity as a fuel source?

Back 9

more expensive in most parts of the country compared with other fuels
utilities often charge more for peak use

Front 10

Steam as a fuel source would most likely not be available in:
a. a rural area
b. in an urban industrial area
c. near an electricity generating plant
d. in an urban city core

Back 10

a. a rural area

Front 11

a heat pump can provide

Back 11

heating in the winter and cooling in the summer

Front 12

the efficiency of heat pump that uses outdoor air decrease as the outdoor temperature approaches

Back 12

40 deg F.

Front 13

Below _______ a heat pump is not competitive with oil or gas.

Back 13

40 deg F.

Front 14

This is a diagram of:

Back 14

the compression refrigeration cycle

Front 15

A solar energy system can be added to a ____________ to increase its efficiency between 47F and 65F

Back 15

heat pump

electric resistance heating can be added to handle very cold or cloudy days

Front 16

what are the natural energy sources

Back 16

solar
photovoltaic
geothermal
wind
tidal

Front 17

of all the natural energy source options, which technology is the most developed

Back 17

solar

Front 18

what are the key things for selecting the fuel source for a project

Back 18

1. # of degree days at a buildings location &
2. the efficiency of the fuel

Front 19

what are the two most common pieces of heat generation equipment

Back 19

furnace & boiler

Front 20

check all of the following that are boiler fuels:
a. gas
b. oil
c. steam
d. electricity

Back 20

all of them

Front 21

name the three types of refrigeration

Back 21

compressive
absorption
evaporative

Front 22

The National Electrical Code is also known as NFPA ____?

Back 22

NFPA 70

Front 23

describe how absorption refrigeration works

Back 23

it produces chilled water & is accomplished by the loss of heat due to evaporation

Front 24

what is a scenario where absorptive refrigeration would work

Back 24

when you have waste heat readily available for input into the generator.

Front 25

describe evaporative cooling

Back 25

air is pulled through moist pads where it is cooled through evaporation & is circulated through the building by a large blower.

Front 26

advantages & disadvantages of evaporative cooling

Back 26

adv: simpler & more economic system compared to refrigeration cooling, works well when humidity levels are low, outside air can be cooled by as much as 30 deg.
dis-adv: required sufficient difference in humidity to work, increases humidity level indoors, efficiency decreases as outdoor humidity increases.

Front 27

1 ton of refrigeration =

Back 27

12,000 BTU

in general, the required capacity of a refrigeration machine can be determined by dividing the total heat gain in BTU/hr by 12,000

Front 28

HVAC systems are categorized by

Back 28

the medium used to heat or cool

Front 29

the 2 primary hvac systems to transport heat are

Back 29

air and water

electricity can also be used directly for heating
some systems use a combination of media

Front 30

what is a dx unit and what are its characteristics

Back 30

DX = direct expansion unit. Also known as an incremental unit.
characteristics: self contained, passes non-ducted air over evaporator and back into room, condenser uses outdoor air directly, usually placed on exterior wall, 1/3 to 2 ton units usually adequate for 1 room. Larger units can serve multiple rooms in one zone. can also have heating, can be through wall, through roof, or packaged.

Front 31

what is an all-air system and what are its characteristics

Back 31

all-air systems cool or heat spaces by air alone,
most basic system is constant volume.
single duct system (what we have in our house)
can be found in small commercial applications
has a central t-stat
simple, easy to operate,
can't be zoned
only can adjust dampers on each supply register

Front 32

for larger buildings there are 4 basic types of all air systems. name them.

Back 32

vav
high velocity, dual duct
constant volume with re-heat
multi-zone

Front 33

what is a good situation to use a VAV system

Back 33

used where temperature regulation is needed, humidity control is needed, and energy conservation is a concern.

Front 34

describe a VAV system

Back 34

air is heated or cooled in a central plant & distributed through single duct at constant temperature
at each zone a t-stat controls a damper that varies volume of air.
dampers introduce fresh air on return side for ventilation & when outside air doesn't need to be conditioned
limited ability to compensate for extremes in simultaneous heating & cooling demands
very efficient means of air conditioning large internal load dominated buildings.

Front 35

what is a good situation to use a high velocity dual duct system?

Back 35

used where more flexibility is required.

Front 36

describe a high velocity dual duct system

Back 36

uses 2 parallel ducts - 1 hot, 1 cold
the 2 ducts are joined at a mixing box
pros: can respond to varying requirement
because of high velocity the ducts can be smaller which saves space.
cons: inherently inefficient because hot & cold air are both supplied & previously heated or cooled air may have to be invertedly conditioned
because of higher velocity, larger fans are required
high velocity can cause noise problems
initial cost is high because of extra ductwork

Front 37

describe a constant volume w/re-heat system

Back 37

takes return air & fresh air and cools & dehumidifies the mixture, then distributes them through the building. At or near the spaces to be conditioned the air is reheated as required by the cooling load of the space.
reheating usually done with heated water, but can be elec.
if reheat is located near the space it is called a 'zone reheat system'
t-stats control valves in water supply line to regulate temperature

Front 38

describe pros and cons of constant volume w/re-heat system

Back 38

pros: humidity & temperature are carefully controlled, low supply temp means smaller duct sizes & fan hp.
cons: uses more energy than some systems because primary air volume must be cooled most of the time, then reheated.

Front 39

what is a good situation to use a constant volume w/re-heat system

Back 39

when humidity and temperature must be carefully controlled.

Front 40

list the characteristics of a multi-zone system

Back 40

supplies air to a central mixing unit where separate heating & cooling coils produce hot & cold air streams. mixed with dampers controlled by zone t-stats

Front 41

list the pros and cons of a multi-zone system

Back 41

pros: offers same advantage as dual duct systems in that simultaneous cooling & heating of different zones can be accommodated.
cons: duct spaces increases rapidly as zones are added.
usually only used for medium sized buildings where central mixing unit is located on each floor.

Front 42

describe all water systems

Back 42

uses a fan coil in each conditioned space connected to 1 or 2 water circuits
ventilation occurs through the wall where the fan coil is located
2, 3, or 4 pipe systems

Front 43

name the pros and cons of all water systems

Back 43

pros: efficiently transfer heat
easy to control
t-stat in each room w/fan coil
cons: humidity control not possible @ central unit

Front 44

describe 'air/water systems'

Back 44

rely on a central air system to profide humidity control & ventilation
majority of heating & cooling provided by fan coil units in each space
these systems are often used where return air can't be recirculated, such as hospitals & labs where 100% of return air is exhausted.

Front 45

name the two types of air/water systems

Back 45

1. induction system - air supplied @ high pressure & velocity to each induction unit where velocity & noise are attenuated before air passes over coils & is heated or cooled as required. can be 2 or 4 pipe system. t-stat regulates water flowing over coils.
2. fan coil w/supplementary air - uses fan coil for primary heating & cooling & has separate constant volume (tempered air supply for humidity control) and ventilation air.