Chapter 10

Question 1

Temperature at which saturated vapor first starts to condense.

Answer 1

Dew point

Question 2

Used for system pump down trapping refrigerant in the receiver enabling the technician to service the low-pressure side.

Answer 2

Front seated

Question 3

Adding refrigerant to a system.

Answer 3

System charging

Question 4

A service valve at the liquid receiver’s outlet.

Answer 4

King valve

Question 5

Measured at the suction line before it enters the compressor.

Answer 5

System superheat

Question 6

Can be accomplished using an electronic scale that can be adjusted to zero with a full cylinder.

Answer 6

Weighing refrigerant

Question 7

Temperature at which bubbles begin to appear in a saturated liquid. Used to calculate subcooling on a system that operates with a blend.

Answer 7

Bubble point

Question 8

Normal operating position of the valve when system is running.

Answer 8

Back seated

Question 9

When some of the blend condenses or evaporates before the rest of the blend does.

Answer 9

Fractionation

Question 10

Normally accomplished in the liquid line.

Answer 10

Liquid refrigerant charging

Question 11

When a refrigerant blend has different temperatures when it evaporates and
condenses at a single given pressure.

Answer 11

Temperature glide

Question 12

Used to add refrigerant to smaller air conditioning and refrigeration systems such as
domestic refrigerators and window or through wall air conditioners.

Answer 12

Graduated charging cylinder

Question 13

Valve position used when charging or recovering refrigerant from a system.

Answer 13

Mid seated

Question 14

Programmable device that will stop the charging process once the desired amount of
refrigerant has been charged.

Answer 14

Electric charging scale

Question 15

When charging a system with a low pressure control and the control keeps shutting the compressor off, you should

a. warm the refrigerant cylinder
b. bypass the pressure control until there is sufficient pressure to keep the compressor running.
c. let the system stand for 2 hours for the pressure control to self-adjust.
d. Come back the next day.

Answer 15

b. bypass the pressure control until there is sufficient pressure to keep the compressor running.

Question 16

Refrigerant in vapor form is normally charged into a system through the

a. liquid line
b. receiver
c. hot gas line
d. suction line

Answer 16

d. Suction line

Question 17

When throttling in liquid refrigerant through the suction line, do not exceed ______ psig above the suction pressure to prevent liquid refrigerant from entering the compressor.

Answer 17

10 psig

Question 18

List four items/tools required to check a system’s subcooling or superheat for the correct charge.

Answer 18

Thermometer, pressure gauges, curve chart, PT chart.

Question 19

Bubble point is used to calculate subcooling of a blend refrigerant.
T/F

Answer 19

True

Question 20

R-401A at a pressure of 85.3 psig has a vapor temperature of 75.08°F and a liquid
temperature of 67.79°F. It has a temperature glide of 7.29°F.
T/F

Answer 20

True

Question 21

R-134a at a pressure of 89.3 psig has a vapor temperature of 81.7°F and a liquid
temperature of 81.7°F. It does not have a temperature glide.
T/F

Answer 21

True

Question 22

The condensing temperature of a refrigerant blend is the average of the liquid and
vapor temperatures added together and then divided by two.
T/F

Answer 22

True

Question 23

A system using R-407C has a discharge pressure of 125 psig and the liquid line temperature at the exit of the condenser measures 90°F. The subcooling for this system is 10°
T/F

Answer 23

True

Question 24

Always let the system run for at least 15 minutes after recovering or adding refrigerant to a system before recalculating superheat.
T/F

Answer 24

True

Question 25

A bathroom scale can be used to weigh a refrigerant charge into a system. T/F

Answer 25

False

Question 26

When working with blended refrigerants, the refrigerant must leave the cylinder as a liquid to prevent fractionation. T/F

Answer 26

True

Question 27

Concentrated heat from a torch can be used to heat a refrigerant cylinder to increase the pressure within the cylinder. T/F

Answer 27

False

Question 28

If the lower portion of the compressor casing becomes cold and frosty when throttling liquid refrigerant into the suction line, stop adding liquid refrigerant. T/F

Answer 28

True

Question 29

A unit with high super heat would indicate a ____ evaporator coil

Answer 29

Clogged or starved

Question 30

Charging by liquid through the suction line could overload the compressor from refrigerant vapors that are too dense. What tool would you use to monitor how hard the compressor is working?

Answer 30

Clamp multimeter

Question 31

A charging cylinder is loaded with 4 lb 4 oz of refrigerant. 28oz of refrigerant is charged into a system. How much refrigerant remains in the charging cylinder? Give your answer in pounds and ounces.

Answer 31

2 lb and 8 oz

Question 32

To front seat a valve, turn it right or left?

Answer 32

Right

Question 33

You are adding liquid to the suction line. As a safety precaution to prevent liquid from entering the compressor, you would place the suction service valve in the______ position.

Answer 33

Cracked off the back

Question 34

Refrigerant cylinder pressure is 150 psig. Discharge pressure of the system is 350 psig. Refrigerant must be charged into the system through the______ line until the pressure in the cylinder reaches____ psig.

Answer 34

Suction , 150 psig

Question 35

When using a tub of warm water to increase pressure in the cylinder, the water temperature should not exceed____ F°

Answer 35

90°

Question 36

Dewpoint is the temperature at which saturated vapor first starts to____.

Answer 36

Condense