Commercial Air Conditioning

The pressure in a duct system is measured in

"WC

The atmosphere exerts a pressure of _________ at standard atmospheric conditions

14.696 psi

A ___ degree F temperature difference from inside the duct to outside the duct is considered the maximum difference allowed before insulation is necessary

15

Flexible round duct comes in sizes up to about ______in. in diameter

20

If the equivalent lengt of a transition piece of ductwork is 10 feet and the main duct in series with it is 20 feet what is the length used to estimate the total frictional loss

30 feet

The __________ or fan provides the pressure difference to force the air into the duct system

Blower

Friction due to air rubbing the walls of the ductwork

Can not be eliminated

The reason for using a reducing extended plenum system is to

Maintain a more even pressure throughout the entire length of the trunk duct

Baseboard hot water heat is an example of _____________ heat

Natural draft

Duct systems can be

Plenum, reducing plenum, or perimeter loop

Canvas collars are generally made of

Rubber or other materials not canvas

One reason for using a reducing plenum system is to

Save materials and keep the duct pressure constant

Oversized duct systems can result in

Slowing of the air as it flows through duct and higher cost

Measuring velocity pressure in a duct indicates the

Speed at which the air is moving

Which of the following is typically measured with a water manometer

Static pressure in a duct system

The __________ of a section of sheet metal is directly related to its weight

Thickness

The forced-air system is different from natural-draft system, where the air passes naturally over the conditioning equipment

True

The duct pressure equals the

Velocity plus static pressure

An instrument used to measure the actual air velocity is the

Velometer

An air pressure measuring instrument

Water manometer