3E1X1 Air Force
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When using a halide leak detector, the bluish flame turning green indicates...
a refrigerant leak
On a manifold gauge assembly, the vacuum hose is 3/8 inch and the other hoses are 1/4 inch because larger sizes allow for...
fewer restrictions which makes it easier and quicker to pull a vacuum
Why should the manifold gauge assembly not be used when measuring a vacuum?
The gauge assembly reads inches of mercury and is not accurate when pulling deep vacuums
While taking a reading with an infrared thermometer, what happens as you get further from the object being measured?
The reading becomes more inaccurate
What part of the combustion analyzer gets placed into the stack?
The probe
What transfers flue gases from the boiler stack to the indicator unit?
A tube and hand bulb
The special slide-rule calculator and CO2 indicator are used to determine...
combustion efficiency and stack loss
What will occur if you choose more than one conductor to measure when using a clamp on meter?
Incorrect readings
A megohmmeter should never be used on a live circuit because...
if has its own power source and it will ruin the meter
A capacitance checker is used to test...
a capacitor
A photo tachometer is used to read the...
revolutions per minute (RPM) of a spinning motor shaft
When using the stroboscope, the frequency and reading is displayed for the technician when the object appears to be...
standing still and the rpm of the equipment matches
What pressure will be given if both tubes are connected to the inclined manometer?
Velocity pressure
Magnehelic pressure gauges were developed to...
overcome the disadvantages of the inclined and inclined vertical manometer
Why does the magnehelic gauge need more frequent calibration?
Because it is a mechanical instrument and is sensitive to physical abuse, dirt, dust, corrosive gases, and fluids
Why is the accuracy at the filters, louvers, and coils very rough?
Due to the uncertainty of the Ak (correction factor) area****
In order to be measured by the flow hood, how is all of the air forced to flow through the diffuser or grille?
A flow hood or capture box completely surrounds and covers a diffuser or grille
When are flow hoods especially practical?
In existing buildings where the manufacturers or Ak factors of the outlets are not known
If you need a tool that functions as a balancing flowmeter you should select...
a circuit tester
When pipe is needed for a high pressure application you should select...
extra strong pipe
Pipe should not be threaded when it is...
a wall thickness less than standard weight
When would flanges be installed?
Wherever it may be necessary to open the joint for service or replacement of components
What must be done before you apply pressure on the dies?
Be sure you have the oil running to help start the segments on the pipe
How are the die segments released?
Release lever
After you clean the threads of the fitting with a wire brush, what is the next step?
Apply a small amount of pipe joint compound to the male threads
After you screw the fitting hand tight on the pipe in a clockwise direction you immediately...
select a pipe wrench size
After you screw the coupling on the pipe hand-tight without using a vise, the next step is to?
select two wrenches
Aluminum tubing is mostly used in...
the manufacture of evaporators for domestic refrigerators
Stainless steel tubing is used
with milk-handling systems, ice cream manufacture, and in food processing
If you are required to make connections between steel pipe and copper pipe, which fitting would you choose?
An adapter
What is done immediately after the tubing has been cut with a tube cutter?
Use the tube reamer on the cutter to remove the burr inside the tube
The first step in cutting tubing with a hacksaw is to select which hacksaw blade
32 teeth per inch
After slipping the nut on the tubing the next step is to
insert the end of the tubing into the correct-sized hole in the flaring block
When fabricating a single flare, the next step after you tighten the block's clamp is to
place refrigerant oil on the flaring cone
The gate valve is not suitable for throttling flow because
the velocity of flow against the partly opened valve may cause vibration and damage
What does the mixing valve do when the leaving water temperature rises above set point?
It will throttle back the hot water and "open up" the cold water
What position should the service valve be in during normal operation?
Back seated
Cracking a service valve will
prevent a pressure rush
What type of cross connection exists if the spout on a sink faucet extends below the overflow rim?
Indirect
What hazard may cause a significant change in water quality?
Class II.
When should the air gap be used?
Whenever possible
To completely burn acetylene, it is not necessary to supply all 1½ parts of oxygen because
a portion of the oxygen is derived from the air surrounding the flame
When will the safety plugs in acetylene cylinders melt?
212 to 220 °F
Care must be taken to prevent propane/butane torch hose damage to
prevent a possible fire
What is the last step in operating the propane/butane torch?
Store the assembly in a safe and cool place
Oxygen valve threads are right handed to
keep you from confusing the oxygen connection with the acetylene connections
The gases from the oxygen and acetylene cylinders are mixed in the
mixing head
How can a regulator leak be detected?
A gradual pressure rise on the working pressure gauge after the cylinder or manifold valve is opened.
What could occur if copper is used to replace a brass hose splice?
Copper acetylene is formed which explodes violently
Each acetylene and oxygen cylinder valve is cracked to
blow out any dirt that may be lodged in the outlet nipple
What is the first step in disassembling an oxyacetylene outfit?
Be sure the gas supply is off
Using a torch wrench helps prevent
rounding of corners on connecting and union nuts
Soft metals are used for soldering because
they have low melting points
What is the next step after you think the metal is at the solder's melting point and you place the flame at the center of the fitting?
Touch the solder to the bottom of the joint
What is a cause for solder not staying on a joint?
The melting point and flow points are too close together.
Why should 95/5 solder never be used on the discharge line of a refrigerant system?
It will become weak and leak
How is energy used in the HVAC/R career field?
It is converted
Water sitting at a valve will be potential energy until
a technician opens the valve and allows the water to flow.*****
When the flow of heat is not reflected in a temperature change, what type of heat change is taking place?
Latent heat.
Molecules closest together when an object is
a solid
If pipes are warm and the air is cool, how will the air be warmed?
The transfer of heat to the cooler air
When a fan propels air across a hot or cold surface, what generally increases heat transfer?
An increase in velocity
When are static measurements taken on an air system?
While the fan is moving air
Velocities measured at different points in the same cross-section of a pipe or ducts are not the same because
molecules may slip against each other
If there is no fluid flow in the system, then TP = SP, or...
system pressure at any point is equal to the static pressure at that point
In a closed system with constant pressure, if the temperature increases the
volume will increase
Why is it impossible to superheat steam in the presence of boiling water?
All the added heat only evaporates more water until all the water has boiled to steam
What will the dry-bulb, wet-bulb, and dew point temperatures be when air is saturated?
They will all be the same
If the spray water is colder than the dew point of the entering air, the sprays will
dehumidify the air
When is solar loading averaged?
Throughout the day
What is the final step of heat load calculations?
Review and trust your work
What is the first step in determining equipment sizing?
Select the correct equipment
After selecting the correct equipment, the next step is to
order the unit
If equipment cannot keep up with the load, what could be assumed about the system?
It is undersized
What is the final step when finding mistakes with sizing?
Check current facility use
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