LTE 105 MidTerm Review

What percentage of moisture and particles must be removed from reclaimed refrigerants?

100%

Calculate the tare weight of a cylinder if its total weight is 590 lb and the weight of refrigerant in the cylinder is 450 lb

140 lb

What is the sueprheat of a system if the refrigerant temperature in the suction line is 58 degrees F, its pressure in the evaporator is 60 psig, and its temperature in the evaporator is 34 degrees F

24 degrees F

A gauge should not be exposed to pressure greater than__ of its full-scale range for more than a few minutes

75%

What is the maximum amount of refrigerant that a recovery cylinder should contain?

80% water capacity by weight

All refrigerant cylinders should be secured with __ whey they are being transported

A Chain

Halogens cause the torch of a flame to turn__ when they are brought into contact with heated copper

Green

Because they cannot be mixed with mineral oils, __ refrigerants use synthetic oils for lubrication

HFC

According to the ASHRAE classification for refrigerants, the classification for the least toxic and least flammable refrigerant is

A1

A vapor refrigerant is superheated if its temperature is__ the refrigerant's boiling point

Above

Low-pressure refrigerant has the potential to __ heat

Absorb

If the valve system is turned counterclockwise as far as possible, the service vale is in the __ position

Back Seated

Due to their high ozone depletion potential, __ refrigerants were targeted first for phase out by the Montreal Protocol

CFC

During push-pull liquid recovery, vapor refrigerant is pulled from the __

Compressor

A suction service valve connects to the suction line and directly onto the

Compressor at its inlet

To determine a system's subcooling value, the liquid line temperature should be subtracted from the __ temperaturew

Condenser

Subcooling refers to the amount of __ removed from a refrigerant after is has condensed

Sensible Heat

A pressure-temperature curve shows that pressure and temperature are __ in a refrigeration system

Directly Related

All refrigeration systems must have accumulators to operate safely

FAlse

Disposable cylinders are designed to be used for refrigerant recovery

FAlse

To release refrigerant dissolved in compressor oil, an oxyacetylene torch should be used to heat the compressor

FAlse

A decrease in temperature can cause the pressure in a cylinder to increase

False

A gauge that reads absolute pressure should be adjusted depending on the elevation.

False

A liquid line filter drier is installed int he low side of the system

False

A reciprocating compressor uses one or more pistons that move in only one direction

False

A superheated vapor contains some refrigerant in liquid form

False

Active recovery uses an HVACR system's compressor to pump refrigerant into a recovery cylinder

False

CArbon dioxide is classified as an organic refrigegrant(600 series)

False

Cylinder color-coding is a requirement for manufacturers, so technicians do not need to check labels.

False

Electronic leak detectors can only be used to detect CFC's

False

HCFC's have an ODP rating of 0

False

HFC's were the first type of refrigerant to be produced

False

Longer vacuum pump service lines are more effective at pulling a vacuum than shorter service lines

False

Refrigerant in the form of low-pressure vapor has the highest capacity to absorb heat

False

Refrigerant is reclaimed on the job site

False

Refrigeration systems that use capillary tubes as refrigerant metering devices must have a liquid receiver in order to work properly

False

Service Valves are front seated for normal system operation

False

Service technicians can safely use formulas and tables to mix their own azeotropic refrigerant blends

False

Suction lines are generally smaller in diameter than liquid lines

False

The amount of refrigerant that a cylinder can safely hold is 90% of the volume of water that it can hold

False

The refrigerant charge in a system with a fixed orifice metering device should be checked by subcooling

False

The refrigerant temperature in the evaporator is the same as the evaporator temperature when the unit is running

False

Two-part epoxy resins must be heated in order to harden

False

PAssive recovery is generally used on larger systems

Fasle

Both valves need to be closed on a gauge manifold in order to evacuate a system.

Flase

The instantaneous evaporation of liquid refrigerant when it enters the evaporator is called the __

Flash Gas

The separation of the individual refrigerants in a zeotropic blend during phase change is known as __

Fractionation

Two-part epoxy resin kits usually include one tube filled with epoxy and another tube filled with a _

Hardener

Which of the following is not a type of metering device used to control the flow of refrigerant

Hermetic float

Heat is rejected out of a refrigeration system on the __ side of the system

High

Which type of gauge is designed to read pressure values on a single continuous scale and be used on the high side of a system?

High-pressure gauge

During normal operation, refrigerant pumped int o a condenser is in the form of

High-pressure vapor

If the entire refrigerant charge has leaked out of a system, then a __ should be used to pressurize the system to test for leaks

Inert gas

If a refrigerant belongs to the 700 series in the refrigerant numbering system, then it is

Inorganic

A suction line should be __ to prevent moisture in the air from condensing on the cold tubing

Insulated

Many recover cylinders use a __ as a safety device to turn off the recovery machine when the cylinder is 80% full

Liquid level switch

A compressor is designed to draw in __ refrigerant from the evaporator

Low-pressure Vapor

When charging a system with refrigerant, the technician should put the low- and high-side service valves in __

Mid-position

Drawing an extremely low pressure in a refrigeration system is necessary to remove__ from the system

Moisture

How many times can an expendable refrigerant be used?

Once

Pressure that is greater than atmospheric pressure is referred to as __ pressure

Positive

The lowest temperature at which a lubricant will flow is called the

Pour Paint

The process of pumping a systems entire refrigerant charge in tot he liquid receiver is called __

Pump-down

Which zeotropic refrigerant blend is used as a replacement for R-22 in air-conditioning applications, but operates at a higher temperature and pressure?

R-410A

Refrigerant_ is the process of removing refrigerant from a system and storing it in a cylinder

Recovery

Which type of refrigerant cylinder is gray on the bottom and yellow on the top

Recovery

A bourdon tube __ as pressure inside it increases

Straightens

If heat is added to a saturated vapor and raises the vapor's temperature above its boiling point, the heat is referred to as

Superheat

The fins on an evaporator increase the __ of the evaporator tubing, allowing increase heat transfer from the air to the tubing

Surface area

When a refrigeration unit is off, the temperature of the condenser is __ the temperature of the refrigerant.

The Same as

Which evacuation method involves charging a system with nitrogen to absorb moisture?

Triple evacuation

A higher coefficient of performance means that a refrigerant produces its refrigeration effect more efficiently

True

A refrigerant blend containing an HCFC and CFC is considered a CFC

True

A refrigeration system reaches operational balance when the number of vapor molecules that condense into liquid equals the number of vapor molecules that the compressor pumps in to the condenser

True

A small amount of oil circulating throughout a refrigeration system is generally considered acceptable

True

A system should have low-pressure flowing nitrogen within before a leak is fixed by brazing

True

Each time a recovery-recycling machine is used, the filter-drier should be changed

True

Fluids that are used to boil and absorb heat are called refrigerants

True

In a zeotropic refrigerant blend, the refrigerant wit the the lowest boiling point boils first

True

Push-pull liquid recovery should not be used in systems with less than 5 lb of refrigerant charge

True

R-134A has been used a is a replacement refrigerant for systems that use R-12

True

R-22 and R-123 are classified as HCFC refrigerants

True

Recovery cylinders are often equipped with two valves: one for vapor and one for liquid

True

Refrigerant must be recovered from a leaking system before repairs can be performed

True

The liquid receiver service valve ( king valve) should be front seated in order to perform a pump-down

True

The pressure of a perfect vacuum is 29.92 in . Hg

True

VApor recovery must be used in combination with liquid recovery to recover a systems entire refrigerant charge

True

Zeotropic refrigerant blends should be charged as a liquid

True

Vacuum pump oil turns __ when it is contaminated by water

White and Foamy

The cylinder color code for R-134a is

sky blue