Final Review

Question 1

Cap tube/fixed bore metering device what do you charge with?

Answer 1

Superheat

Question 2

TXV metering device, charges with ?

Answer 2

Subcool

Question 3

What’re two ways you can bring in fresh air in? Which one is mechanical?

Answer 3

Ventilation + infiltration
Ventilation is mechanical

Question 4

Comfort cooling will it cause the evaporating to ice up if it has too much airflow? Or low airflow?

Answer 4

Low airflow due to too much heat picked up.

Question 5

Two main type of control ?

Answer 5

Pressure & Tempature

Question 6

CFM required per ton?

Answer 6

400 CFM

Question 7

Summertime indoor temp?

Answer 7

75/50

Question 8

Air at 95F how much do you add based on refrigerant?

Answer 8

R-22 +30
R410A +10-15

Question 9

What would be the condition of refrigerant going into the txv valve?

Answer 9

100% liquid in
75% liquid out

Question 10

Comfort cooling boils refrigerant around 40F what is the tempature difference ?

Answer 10

20F

Question 11

What is Low superheat?

Answer 11

Overcharge

Question 12

What is high superheat ?

Answer 12

Undercharge

Question 13

High subcool is what ?

Answer 13

Overcharge

Question 14

Low subcool is what ?

Answer 14

Undercharge

Question 15

How are two 24v transformer wired?

Answer 15

In parallel and in phase

Question 16

How are two 24v transformer wired?

Answer 16

In parallel and in phase

Question 17

Whats the desired normal subcool for medium tempature?

Answer 17

10-15

Question 18

Desired normal superheat for medium tempature?

Answer 18

8-12

Question 19

Dry bulb + Wet bulb equals what ?

Answer 19

Relative Humidity

Question 20

Whats the AMP draw of 75amps and 24 volts?

Answer 20

75VA divide by 24v = 3.124

Question 21

What causes lower than expected head pressure ?

Answer 21

Undercharge, not low subcool or Amp draw

Question 22

What can you use to control head pressure?

Answer 22

VFD
Fan cycling switch
2 stage compressor

Question 23

What 3 trades includes installation?

Answer 23

Mechanical, electrical, sheet metal

Question 24

Low ambient temp? What tempature are you trying to simulate?

Answer 24

95F

Question 25

If txv you check subcool first then right before or after the setpoint what should you check?

Answer 25

Superheat 8-12

Question 26

Amperage on a compressor and reading higher?

Answer 26

Overcharge, plugged up coils, high head pressure

Question 27

What line do you check when checking for superheat?

Answer 27

Suction line

Question 28

What line do you check when checking for subcool?

Answer 28

Liquid line cutlet of condenser

Question 29

Commercial what device to use?

Answer 29

Low pressure control

Question 30

75VA and 40 boiling point whats the differential?

Answer 30

20 degree delta T

Question 31

In a residential split AC system running… ?

Answer 31

Compressor condenser fan evap fan

Question 32

Is it possible to use low pressure control to replace thermostat?

Answer 32

Yes, let it cycle on pressure

Question 33

2 reasons to insulate suction line?

Answer 33

1. To prevent too much superheat to be picked up 2. Prevent condensate from dripping

Question 34

Freezer with defrost, how do we initiate defrost?

Answer 34

Brought into defrost by time, but can also come out from pressure

Question 35

What type of refrigerator is more efficent?

Answer 35

Chest freezer is more efficient, cold likes to flow down

Question 36

Charges on general appliances are they considered critical charge?

Answer 36

Yes

Question 37

When in normal operation, what is the position of the valve?

Answer 37

Backseat

Question 38

When pulling a vacuum whats the position of the king valve?

Answer 38

Midseat

Question 39

Whats the position of the king valve when its shut off?

Answer 39

Front seat

Question 40

Two reasons to go into a pump down?

Answer 40

Service Low side Protect compressor on startup