Unit 10

Question 1

Scale that can be adjusted to zero with a full cylinder

Answer 1

electronic scale

Question 2

Typically used in conjunction with fixed bore metering devices if superheat measurements are shown. Charging curves that rely on subcooling are typically used on systems with a TXV

Answer 2

charging curves

Question 3

Temperature at which saturated vapor first starts to condense

Answer 3

dew point

Question 4

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

Answer 4

fractionation

Question 5

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

Answer 5

front seated

Question 6

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

Answer 6

graduated charging cylinder

Question 7

A service valve at the liquid receiver’s outlet in the refrigeration system

Answer 7

king valve

Question 8

Measured at the suction line before it enters the compressor

Answer 8

system superheat

Question 9

Accomplished by allowing vapor to move out of the vapor space of a refrigerant cylinder and into a refrigeration system

Answer 9

vapor refrigerant charging

Question 10

Used for performing standing pressure tests and for system evacuation or charging

Answer 10

midseated

Question 11

Normally accomplished in the liquid line

Answer 11

liquid refrigerant charging

Question 12

Normal operating position of the valve when system is running

Answer 12

back seated

Question 13

Adding refrigerant to a system

Answer 13

system charging

Question 14

May be accomplished using various scales. Bathroom scales should not be used

Answer 14

weighing refrigerant

Question 15

T/F
The correct way to charge a unit that is low on refrigerant is to recover the remaining charge, compare it to the data plate and then recharge the unit plus the amount that was missing to equal the total charge on the data plate

Answer 15

True

Question 16

T/F
System readings can be taken immediately after adding or recovering refrigerant

Answer 16

False

Question 17

T/F
Bubble point and dew point apply to pure refrigerants

Answer 17

False

Question 18

T/F
The further away from the compressor, the lower the temperature of the liquid line

Answer 18

True

Question 19

T/F
To calculate superheat, subtract the temperature at the exit of the evaporator from the internal temperature of the evaporator

Answer 19

False

Question 20

Front seating the king valve on the receiver prevents liquid refrigerant from reaching the metering device

Answer 20

True

Question 21

T/F
The electric plug on a charging cylinder is used to heat the refrigerant to keep the pressure from dropping when vapor is being removed from the cylinder

Answer 21

True

Question 22

T/F
Once system pressure is equal to the refrigerant cylinder pressure, charging is complete

Answer 22

False

Question 23

T/F
To charge a system with liquid refrigerant, always turn the cylinder upside down

Answer 23

False. If using a new cylinder, liquid comes from the bottom

Question 24

T/F
The further away from the evaporator, the lower the temperature of the suction line

Answer 24

False. It picks up superheat along the lines

Question 25

T/F
Fractionation happens only when the leak occurs as a vapor leak

Answer 25

True

Question 26

To start a system that uses a low-pressure control, _______________

Answer 26

D. (answers B&C)
Place a jumper wire across the low pressure contacts and/or use a screwdriver to close the low pressure control contacts

Question 27

Service valves that have their stems turned all the way clockwise into the valve are referred to as

Answer 27

front seated

Question 28

When large amounts of refrigerant are needed, adding the liquid through the ____________ is preferable to other methods because it saves time

Answer 28

king valve on the receiver

Question 29

The king valve has four positions. What are they?

Answer 29

Front seat, mid seat, back seat and cracked off the back

Question 30

Why must refrigerant be added to the suction side of the system when the system is running?

Answer 30

This is to top off charge according to spec. The high side pressure while in operation will not allow refrigerant to exit the cylinder. While in operation, the vacuum will suck refrigerant into the system

Question 31

How can liquid refrigerant be charged into the suction line without damaging the compressor

Answer 31

You may use a commercial liquid line restrictor. You can also crack the service valve off the back and throttle the manifold gauge no more than 10 psig

Question 32

Use supplied system charging chart to determine subcooling, more or less refrigerant, type of metering device given the scenario

Answer 32

Refer to charging chart plate example

Question 33

Be able to determine subcooling/superheat based on scenario given

Question 34

What is the formula for estimating condensing pressure for a high efficiency/micro channel condensing unit?

Answer 34

High- add 30 degrees F to the ambient temp to get internal temp of condenser and convert to psig.
Micro channel- add 15 degrees F to ambient to get internal and convert

Question 35

Noncondensables in a system can cause what types of problems in a system?

Answer 35

This will cause moisture which can result in acid and sludge. The system can also have higher pressures resulting in system inefficiency

Question 36

What does the gas ballast feature on a vacuum pump do?

Answer 36

It allow a measure of atmospheric pressure to balance when pulling vacuum. This extends the life of pump and oil

Question 37

T/F
When checking superheat on a unit that uses refrigerant blend, use the bubble point figures

Answer 37

False