HVAC Midterm 1

A system in cooling mode should provide at least ______ cfm of air per person

15

A rectangular duct with a ______ aspect ratio can hold the max amount of air using the min amount of material

1:1

Air with 75% relative humidty contains _______ of the moisture it is capable of holding

3/4

Degree day calculations are based on a temperature of _____

65 deg F

Duct air velocities above _____ fpm can cause excessive noise

700

A standard that includes equipment and system requirements and minimum ventilation rates that result in acceptable indoor air quality is ____

ASHRAE Standard 62

A fire damper rated for a 2-hour to 4-hour hold is classified as Class _______

B

Which of the following is a valid safety precaution of servicing a rooftop unit?

Before working on equipment, secure hinged panels in the open position; extend the top of the ladder 3' above the edge of the roof; use a rop to lift equipment, tools, and refrigerant cylinder to the roof

If a chiller system could only use one compressor but needed to provide 2000 tons of cooling capacity; which type of compressor is most likely to be used?

Centrifugal

The ACCA developed Manual ______ to be used to design both the supply and return ducts of a building

D

To being fresh air into a building's conditioned space and minimize how much it might affect indoor temperature, use a _________

HRV or ERV

Which of the following is a trait of a packaged outdoor air-conditioning unit?

The supply and return ducts pass through the exterior wall of the building

Central humidifiers are typically supplied with water from _______

a building's tapped water lines

Which of the following best explains the differences between a double-effect adsorption system and single-effect adsorption system?

a double-effect absorption system has both a primary and secondary generator

Common installation locations for UV lights for germicidal protection include:

above the evap coil, inside the evap coil, and in the return air duct

In an absorption system, a substance that soaks up the refrigerant returning from the evaporator is called the __________.

absorbant

Which of the following is the process in which a substance attracts and combines with another substance to form a uniform solution?

absorption

Which of the following is the process in which a solid attracts and holds a substance on its outer surface?

adsorption

Being a measure of ventilation rate, ___________ refers to the replacing of the entire volume of air in one hour

air changes per hour (ACH)

According to ASHRAE, the process to treating air so as to control simultaneously temperature, humidity, cleanliness, and distribution is called _______

air conditioning

Which of the following instruments is used to measure air velocity?

anemometer

The ratio of a duct's wide side to its narrow side is called the _______

aspect ratio

Ultraviolet lights are used to reduce __________

bacteria, mold spores, viruses, and other microorganisms

A _____ damper is used in round ducts

butterfly

Humidifying an entire building's conditioned space, central humidifiers are categorized by the following installation types of humidifiers:

bypass, plenum-mounted, and under-duct

A ____ filter is often used in refrigerators bc of its ability to reduce odors

carbon

The secondary refrigerant used in a chiller system _____

circulates through the conditioned space to provide cooling

The conditions that are normally maintained in an indoor space are referred to as its __________

climate

Using waste heat from one process to power another process is referred to as __________.

cogeneration

When an absorption system is operating, high pressure is maintained in the ___________.

condenser and generator

The purpose of a cooling tower connected to an HVAC system is to _______

cool condenser water

A chiller system uses a loop of _____ to provide cooling to a conditioned space

cool water

For servicing ammonia absorption systems, it is important that the gauge manifold, valves, lines, and fittings used should never be made of ____________.

copper

A water and lithium bromide solution should not be exposed to air to prevent the solution from becoming ____________.

corrosive

A large RTU is most frequently conveyed to a rooftop using a ____

crane

To prevent oil canning when a blower starts and stops, _____ any large panel of sheet metal ductwork

cross-break

Reciprocating compressors are capable of capacity control through __________

cylinder unloading

When a humidifier adds moisture to air already heated by a furnace, the temperature of the air __________.

dec. somewhat

When air temp reaches 100% relative humidity, it is at its ____ point

dew

Starting at sea level and rising higher in altitude through the troposphere, atm pressure ___

drops

A rooftop unit can provide "free cooling" if it is equipped with an

economizer

Fresh air is delivered into a home-s interior by ____

energy recovery ventilators, heat recovery ventilators, humidifiers

High humidity outdoors can prevent rooftop unit's free cooling operation when the system has ________ control

enthalpy

Roof misting and roof ponds are examples of __________ cooling systems.

evaporative

Moisture from air passing through a dehumidifier condenses on its ___________.

evaporator

When an absorption heat pump is in heating mode, ____________.

evaporator acts like a condenser

For a building to maintain positive pressure with various fuel-burning appliances operating, a ____ should be used

fan or blower

Before condensation spills out of a dehumidifier, its ____________ shuts off the compressor, stopping the production and accumulation of moisture.

float switch

Which of the following is a gaseous pollutant?

fumes

In an absorption system, refrigeration is boiled out of the refrigerant-absorber solution in the _____________.

generator

When humidity is too high in a building, the following events may occur:

growth of mold, bacteria, and fungus; formation of condensation on cold surfaces; swelling of hygroscopic materials

While compression systems use mechanical energy to power refrigeration, absorption systems use __________ energy to do the same.

heat

Positive pressure (higher than atmospheric pressure) can be maintained in a building to _____________

help keep out airborne dirt, dust, and pollen

The operation of a pressure water valve is in reaction to ____________

high-pressure water

Wet roof cooling is most effective in ___________.

hot and dry

A traditional electromechanical humidistat senses humidity using a ____________.

hygroscopic element

Basin heaters are used to prevent ________

ice formation in the cooling tower sump

The Beaufort scale _____

indicates levels of wind velocity

The air flowing into a fan is called an _______ fan

induced

A rooftop unit may provide heat for the indoor climate using the following methods:

integrated gas-fired furnace, oil-fire furnace, or electric resistance heating elements

In a commercial HVAC system, if the thermostat's switch controls a liquid line solenoid valve, which control usually cycles off the compressor?

low side pressure control

Which of the following is a general guidelines for duct design?

make duct runs as short as practical, install the blower in a central location, never install a duct in the end of a plenum

Installing long-radius elbows in ducts _______

minimizes airflow turbulence

A humidistat is a control device that responds to changes in conditioned space humidity by doing the following tasks:

modulate dampers and air mixers, turn on or off a dehumidifier; turn on or off a humidifier

VRF in split commercial air-conditioning systems can effectively match cooling capacity by _______

modulating the flow of refrigerant

A hygrometer is an instrument that measures ______

moisture in the air

Which of the following may be used for a heat source in absorption chillers?

natural gas, steam, and electricity

The following humidifiers are categorized as atomizing:

nozzle-type, impeller-type, and piezoelectric (ultrasonic)

Which of the following are true when an absorption system changes from cooling to heating mode?

one or more valves change position; cool water is passed through the coil in the evaporator; the generator produces heat; water sent to the conditioned space is warmed

Which device is used to prevent spilling of condensate from a ductless split system's indoor unit?

overflow switch

Earth's atmosphere contains about 23% _________

oxygen

Fumes and volatile organic compounds are released from ________

paints, adhesives, and synthetic building materials

Two common types of disposable filters are _____

pleated media filter and fiberglass panel filters

A ________ is a substance that is in some way a detriment to comfort, health, and a desirable environment.

pollutant

The most accurate of the techniques for measuring air filter performance is the ____

prefilter

All of the following water valves provide variable water flow control:

pressure water valves and thermostatic water valves

A pneumatic control system uses ________ for device actuation

pressurized air

Carbon monoxide is ____

produces by the incomplete combustion of fuel

The science of studying the thermodynamic properties of air and water vapor is called _______

psychrometry

UV lamps should be cleaned ____

quarterly

Diminishing air quality of indoor air is due to ___________

reduced infiltration of outdoor air and vapors released from new building materials

The ratio of the moisture content in the air compared to the maximum amount of moisture that the air can hold at its current temperature is called _____________.

relative humidity

Air expands to fill a greater space as _____

relative humidity increases, pressure drops, or temp rises

The purpose of a purge unit is to ___________

remove non-condensables from the system

a _________ installed between the base rail of a rooftop unit and the top edge of the roof curb prevent water from leaking through the opening

resilient gasket

Which shape of ducts provide the least resistance of airflow?

round

Which type of duct is more efficient, round or square?

round

Negative pressure in a building ________

should be avoided, bc it reduces the efficiency of exhaust fans and of fuel-fire appliances, also tends to bring in outside contaminants

When radiant heat strikes a surface that is colder than the radiating body, ______

some of the radiant heat is absorbed into the colder surface

Which of the following statements regarding an indirect-fired absorption system is true?

steam, hot water, or hot gas is produced away from the system and delivered through pipes

When a solution in an absorption system is saturated with refrigerant, it is a(n)____________ solution.

strong

A compression chiller economizer improves system efficiency by __________

subcooling high-side refrigerant before entering the evaporator

Indoor air conditions can also be affected by ___________

sun loads, heat sinks, and heat and humidity migration.

Which type of anemometer is entirely mechanical?

swinging-vane anemometer

Return air inlets should be replaced ________

the maximum distance from the supply duct outlets

Which of the following is true of sheet metal ducts?

used for warm air distribution, usually coated with zinc, and expand and contract as they heat and cool

An ERV is ____

used when humidity control is important

Using their own heat source (electric heaters), ____________ humidifiers add moisture to air by creating steam.

vaporizing

Changing the air in a building is called _________

ventilation

In a residential absorption chiller, the __________ is installed in the air handler plenum.

water type cooling coil