Unit 37

The pressure in a duct system is measured in ____.

• psig

• psia

• in. Hg

• in. WC

The ____ provides the pressure difference needed to force the air into the duct system, through the heat-transfer surfaces in the conditioning equipment, through the grilles and registers, and into the room.

• blower

• forcer

• compressor

• condenser

The atmosphere exerts a pressure of ____ at standard atmospheric conditions.

• 12.696 psi

• 14.696 psi

• 16.696 psi

• 18.696 psi

A(n) ____ can be connected to measure the velocity pressure of the air moving in a duct.

• ammeter

• manometer

• pyrometer

• speedometer

An instrument that is commonly used on air distribution systems is the anemometer, or ____.

• velometer

• manometer

• pyrometer

• ammeter

Airflow pressure in ductwork is measured in inches of ____.

• mercury pressure

• water column

• air pressure

• mercury column

The simple way to check for airflow is to see if you can feel the airflow at a distance of about ____ from each register.

• 2 to 3 ft

• 3 to 5 ft

• 5 to 8 ft

• 8 to 10 ft

The reason for using a reducing plenum system is to ____.

• reduce maintenance costs

• reduce the operating cost of the system

• provide easier means of fastening the takeoff fittings

• maintain a constant pressure throughout the length of the trunk duct

One reason for using an extended plenum system is to ____.

• save materials

• reduce the velocity of the air as the air reaches the last takeoffs on the extended plenum

• prolong the main plenum closer to the farthest supply register

• keep the noise level low

A(n) ____ºF temperature difference from the inside to the outside of the duct is considered the maximum difference allowable before insulation is necessary.

• 10

• 15

• 18

• 20