CDC 3E151 - HVAC/R JOURNEYMAN VOLUME 1

(001) When using a halide leak detector, the bluish flame turning green indicates

a refrigerant leak

(001) 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

(001) 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

(002) While taking a reading with an infrared thermometer, what happens as you get further from the object being measured?

The reading becomes more inaccurate

(003) What part of the combustion analyzer gets placed into the stack?

The probe

(003) What transfers flue gases from the boiler stack to the indicator unit?

A tube and hand bulb

(003) The special slide-rule calculator and CO2 indicator are used to determine

combustion efficiency and stack loss

(004) What will occur if you choose more than one conductor to measure when using a clamp on meter?

Incorrect readings

(004) A megohmmeter should never be used on a live circuit because

it has its own power source and it will ruin the meter

(004) A capacitance checker is used to test

a capacitor

(005) A photo tachometer is used to read the

revolutions per minute (RPM) of a spinning motor shaft

(005) When using a 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

(005) What pressure will be given if both tubes are connected to the inclined manometer?

Velocity pressure

(005) Magnehelic pressure gauges were developed to

overcome the disadvantages of the inclined and the inclined vertical manometers

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

(005) Why is the accuracy at filters, louvers, and coils very rough?

Due to the uncertainty of the Ak ( correction factor) area

(005) 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

(005) When are flow hoods especially practical?

In existing buildings where the manufacturers or Ak factors of the outlets are not known

(005) If you need a tool that functions as a balancing flowmeter you should select

a circuit tester

(006) When pipe is needed for a high pressure application you should select

extra strong pipe

(006) Pipe should not be threaded when it is

a wall thickness less than standard weight

(006) When would flanges be installed?

Wherever it may be necessary to open the joint for service or replacement of components

(007) 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

(007) How are the die segments released?

Release lever

(008)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

(008) After you screw the fitting hand tight on the pipe hand-tight on the pipe in a clockwise direction you immediately

select a pipe wrench size

(008) After you screw the coupling on the pipe hand-tight without using a vise, the next step is to?

select two wrenches

(009) Aluminum tubing is mostly used in

the manufacture of evaporators for domestic refrigerators

(009) Stainless steel tubing is used

with milk-handling systems, ice cream manufacture, and in food processing

(009) If you are required to make connections between steel pipe and copper pipe, which fitting would you choose?

An adapter

(010) 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

(010) The first step in cutting tubing with a hacksaw is to select which hacksaw blade

32 teeth per inch

(011) 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

(011) When fabricating a single flare, the next step after you tighten the block's clamp is to

place refrigerant oil on the flaring cone

(012) The gate valve is not suitable for throttling flow because

the velocity of flow against the partly opened valve may cause vibration and damage

(013) 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

(013) What position should the service valve be in during normal operation?

Back seated

(013) Cracking a service valve will

prevent a pressure rush

(014) What type of cross connection exists if the spout on a sink faucet extends below the overflow rim?

Indirect

(014) What hazard may cause a significant change in water quality?

Class 2

(015) When should the air gap be used?

Whenever possible

(016) To completely burn acetylene, it is not necessary to supply all 1 1/2 parts of oxygen because

a portion of the oxygen is derived from the air surrounding the flame

(016) When will the safety plugs in acetylene cylinders melt?

212 to 220 F

(016) Care must be taken to prevent propane/butane torch hose damage to

prevent a possible fire

(016) What is the last step in operating the propane/butane torch?

Store the assembly in a safe and cool place

(017) Oxygen valve threads are right handed to

keep you from confusing the oxygen connection with the acetylene connections

(017) The gases from the oxygen and acetylene cylinders are mixed in the

mixing head

(017) How can a regulator leak be detected?

A gradual pressure rise on the working pressure gauge after the cylinder or manifold valve is opened

(017) What could occur if copper is used to replace a brass hose splice?

Copper acetylene is formed which explodes violently

(018) Each acetylene and oxygen cylinder valve is cracked to

blow out any dirt that may be lodged in the outlet nipple

(018) What is the first step in disassembling an oxyacetylene outfit?

Be sure the gas supply is off

(018) Using a torch wrench helps prevent

rounding of corners on connecting and union nuts

(019) Soft metals are used for soldering because

they have low melting points

(019) 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

(019) What is a cause for solder not staying on a joint?

The melting point and flow points are too close together

(019) Why should 95/5 solder never be used on the discharge line of a refrigerant system?

It will become weak and leak

(020) How is energy used in the HVAC/R career field?

It is converted

(020) Water sitting at a valve will be potential energy until

a technician opens the valve and allows the water to flow

(020) When the flow of heat is not reflected in a temperature change, what type of heat change is taking place?

Latent heat

(020) Molecules closest together when an object is

a solid

(020) If pipes are warm and the air is cool, how will the air be warmed?

The transfer of heat to the cooler air

(020) When a fan propels air across a hot or cold surface, what generally increases heat transfer?

An increase in velocity

(021) When are static measurements taken on an air system?

While the fan is moving air

(021) 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

(021) 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

(022) In a closed system with constant pressure, if the temperature increases the

volume will increase

(022) 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

(023) What will the dry-bulb, wet-bulb, and dew point temperatures be when air is saturated?

They will all be the same

(023) If the spray water is colder than the dew point of the entering air, the sprays will

dehumidify the air

(024) When is solar loading averaged?

Throughout the day

(025) What is the final step of heat load calculations?

Review and trust your work

(026) What is the first step in determining equipment sizing?

Select the correct equipment

(026) After selecting the correct equipment, the next step is to

order the unit

(027) If equipment cannot keep up with the load, what could be assumed about the system?

It is undersized

(027) What is the final step when finding mistakes with sizing?

Check current facility use