CH 29

Fresh air intakes are especially important in newer construction or in buildings that have been extensively insulated and weatherproofed.

True

Heat is released when water vapor condenses.

True

Ideally, return air ducts would be located both near the floor and the ceiling.

True

Locating an air handler in a central location minimizes the lengths of the longest supply and return ducts.

True

Proper functioning of a heating or cooling system depends on the duct sizes and damper settings.

True

Radial flow fans may be directly driven by the fan motor or driven by a belt and pulley system.

True

Registers that pass from unconditioned spaces into conditioned spaces can be sealed to the drywall or subfloor to reduce heat leakage.

True

Return duct inlets should be located at the farthest distance from the supply duct outlets.

True

The space between a false ceiling and a real ceiling may be used as a return air plenum.

True

When installing a damper, it is helpful to draw a line on the end of the shaft that extends out of the duct to show damper position.

True

When moving cooled air as opposed to moving warmed air, a 30% to 50% airflow increase is usually used.

True

When sensible heat is removed from air, there is a decrease in dry-bulb temperature.

True

The deflectors in registers are stationary and immovable, maintaining a set direction of airflow.

False

The overall size of a supply outlet determines a fixture's capacity.

False

Air circulation depends on the velocity of the air moving through the supply outlets.

True

Fabric joints can be used to absorb noise caused by the expansion and contraction movements of metal ducts.

True

A multiple-blade damper is used primarily in round ducts to control airflow.

False

An intermittent forced air system provides a more constant temperature in rooms than a continuous blower system.

False

As its temperature drops or its pressure rises, air expands to fill a greater space.

False

As relative humidity decreases, each pound of air will occupy a greater space.

False

Cold air holds more moisture than warm air.

False

Ducts should be installed in the end of a plenum for balanced airflow.

False

In a VAV system, the opening and closing of dampers is based on a room's air pressure.

False

The human comfort level for summer is about ____ and 50% rh.

75°F (24°C) db

Which of the following statements about air ducts is true?

Air ducts may be made of galvanized sheet metal.

Which of the following statements about airflow in duct systems is false?

Airflow compression will be reduced through the use of additional 90° elbows.

Which of the following statements about damper controls is false?

All automatic dampers open and close based on the pressure of the conditioned air.

If the rooms in a building are tightly sealed, the ____.

All of the above.

Increasing the static pressure against which a fan must operate increases the amount of airflow delivered by the fan.

False

Residential duct sizing and damper settings must prevent air from traveling too slowly to prevent noise in the system.

False

Which of the following statements about duct systems is false?

Ducts in concrete are made by drilling airways with large drill bits and hole saws.

A butterfly damper is used primarily in square or rectangular ducts to restrict or completely shut off airflow to a room or zone.

False

A decrease of dry-bulb temperature occurs when sensible heat is added into air.

False

Airflow compression will be reduced through the use of additional 90° elbows.

Install ducts off the sides of a plenum, not off the end. Locate the air handler in a central location. Keep duct runs as short as practical. Correct! All of the above.

Which of the following statements about an evaporative cooling system is false?

It decreases the rh level of the air while raising its db temperature.

If there is more return air than supply air in a room, the room will have a ____ pressure.

Negative

Which of the following statements about air distribution systems is false?

Negative pressure in a building decreases the infiltration at windows and doors.

Which of the following statements about fire dampers is false?

Static systems require fire dampers at locations in which fan pressure will be on during a fire.

A cubic foot of air warmed by a standard heating system will change room temperature more than a cubic foot of air cooled by a standard cooling system.

True

Which of the following statements about duct systems installed in concrete is false?

Upflow furnaces are used with this type of installation

Fans used in air distribution systems ____.

are usually axial flow or radial flow

The heat released when moisture condenses out of the air is ____ heat.

l

Air delivered to a room from a supply duct is called ____.

primary air

Diffusers in air distribution systems ____.

spread the air leaving the duct more uniformly than registers

Heat recovery ventilators (HRVs) ____.

use a fan to bring in fresh air from the outside

Automatic fire dampers should be installed in all ____ ducts in commercial and industrial buildings.

vertical