The pressure in a duct system is measured in:
psig
psia
" Hg
" WC
The __________ or fan provides the pressure difference 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
Measuring velocity pressure in a duct indicates the __________.
volume of air through a duct
speed at which the air is moving
pressure against the sides of the duct
weight of the air moving through the duct
An air pressure measuring instrument __________
water velometer
water manometer
air manometer
air velometer
Why we use a reducing plenum system is to __________.
save materials
keep the noise level low
keep the duct pressures constant
both a and c
A(n) _________ degree F temperature difference from inside the duct to outside the duct is considered the maximum difference allowed before insulation is necessary.
15
18
20
22
If the equivalent length 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?
10 feet
30 feet
60 feet
20 feet
What is an air conditioning systems capacity in tons if the supply air is moving through a 12" x 24" main duct at a velocity of 400 feet per minute.
1 ton
3 tons
2 tons
2.5 tons
If you were to use a vane anemometer to check air flow what velocity pressure would you use if your traverse readings were: 475, 500, 500, 450, 500, 525, 550, 500, 450, 500, 525, 475
500 ft./min.
513 ft./min.
500" w.c.
487 ft./min.
One psi is equivalent to:
Atmospheric pressure
34 ft. w.c.
27.7" w.c.
14.7" w.c.
The main reason for using a reducing extended plenum system is to __________.
save metal by using a smaller duct
reduce the operating cost of the system
provide easier means of fastening the take off fittings
maintain a more even pressure throughout the entire length of the trunk duct
The forced-air system is different from a natural-draft system.
The duct pressure equals the velocity pressure plus static pressure.
Adjusting the tension on the belt will alter the rate at which air is moving through the system, but does not affect the amperage draw of the motor.
Canvas collars are generally made of canvas rather than other materials such as rubber.
Oversized duct systems cost more to fabricate and install and will also result in the slowing of the air as it flows through the duct.
The device used to put trunk duct or extended plenum sections together is called a drive clip.
Friction due to air rubbing the walls of the ductwork can be eliminated.
The main drawback of the extended plenum system is that the velocity of the air is lower as the air reaches the last takeoffs on the extended plenum.
