Sheet Metal Finals

Air that enters a structure from leaks around windows and doors is described as

infiltration air

An example of a natural draft system is

hot water baseboard heat.

All of the following are desirable charteristics of a forced air system EXCEPT

equipment cycling is noticeable by the occupants of the structure.

The pressures in a duct system are measured in which units

Inches of water column (IWC)

At standard conditions, atmospheric pressure can support a column of water that is approximately how high?

3.4 ft

The pressure that represents the force pushing outward against the walls of the duct system is referred to as the

static pressure

Which of the following is an accurate expression that relates the three duct system pressures?

Velocity Pressure = Total Pressure - Static Pressure

What instrument is used to measure duct system pressures

manometer.

An anemometer is used to directly measure

speed of air flowing through a duct.

Which of the following sets of instruments are most similar to each other?

anemometer and velometer

Squirrel-cage type blowers are used in conjunction with duct systems because they

are able to overcome the pressures that are present in the duct system.

Which of the following is true regarding the amperage draw of a blower motor being used to move air through a duct system?

motor amperage will go up if the door on the blower compartment is removed.

The type of blower assembly that utilizes both motor shaft and blower shaft bearings is the

belt drive blower assembly.

The type of blower assembly that utilizes only motor shaft bearings is the

direct drive blower assembly.

Which of the following blower assemblies is used in conjunction with changeable or adjustable pulleys that can vary the blower speed?

belt drive blower assembly.

Which of the following is false regarding a duct system that is oversized?

increased noise levels

Which of the following is a benefit of the reducing plenum air distribution system?

The velocity of the air is maintained throughout the system

Which of the following air distribution systems is commonly installed in a poured slab floor?

Perimeter loop system

Rectangular metal duct sections are commonly joined together with

slips and drives

Galvanized sheet metal is treated/ coated with which substance to slow the corrosion process?

zinc

Sheet metal duct sections are often fabricated with cross-breaks to

make the duct more rigid.

Flexible duct

is ideally used for very short, direct runs.

The duct branch system is connected to the main trunk with a

takeoff fitting

A streamlined takeoff fitting is designed with

a throat that is larger than the runout duct it is connected to.

Branch balancing dampers are ideally located

as close to the supply register location as possible.

Volume balancing dampers are ideally located

as close as possible to the air handler/ furnace in the main supply air trunks.

which of the following statements is accurate with regards to simple system zoning?

Zone dampers are automatically operated based on space temperature.

If an air conditioning system has three independent zones, how many space thermostats will the system have?

3

Which of the following are challenges that have to be addressed when a single speed blower motor is used on a zoned air conditioning system?

Reduced airflow, increased noise, evaporator coil freeze-ups.

Ducts are insulated to

prevent duct sweating and decrease the heat transfer rate between the air in and around the duct.

Supply air registers should be positioned and configured so that

the supply air is directed onto the walls of the room.

Duct systems must be properly sized and designed to reduce and overcome the effects of

friction within the duct system.

If there seems to be reduced airflow at all supply register locations, which of the following is the most likely problem with the system?

The system air filter is dirty.

If a gas fired furnace is constantly tripping on a high limit safety control, which of the following is likely NOT the cause for this condition?

Improperly balanced air distribution system

The failure to provide adequate airflow to all areas of a structure may cause areas that are too hot and areas that are too cold.

True

What type of connector is used to connect the lower supply air plenum to the main supply air trunk?

canvas

What type of connector is used to connect the lower return air duct to the main return air trunk?

canvas

What type of instrument can be used to verify airflow in a branch run?

magnehelic

Supply air registers are located

perimeter of home

Return air grills are located

interior of home