Evaporator Feed Controls

Question 1

Electronic expansion devices are able to operate near 0F ?

Answer 1

Yes, and they do not have a sensing bulb

Question 2

If the capillary tube is plugged in the first 6 inches it’s most likely to have what?

Answer 2

Drier desiccant, dirt or copper filings

Question 3

When pressures are equal in AEV ?

Answer 3

Spring pressure = evaporator pressure or p1=p2

Question 4

Z charge temperature range is?

Answer 4

0F to -40F

Question 5

Vapour in the liquid line will dramatically reduce the capacity of TXV?

Answer 5

Yes it’s true

Question 6

A TXV is said to be balanced when P1=P2+P3. Bulb pressure (opening)= evaporator pressure (SSP)(closing)+ spring force (superheat)(closing)

Answer 6

True

Question 7

Sizing a capillary tube is done by?

Answer 7

Using inside diameter and length.

Question 8

An undercharge cap tube system would have symptoms of ?

Answer 8

Low suction pressure
Low discharge pressure
Low amp draw
High superheat

Question 9

Low side float is found on the low side of the system, opens on a low level of the chiller and is used with flooded evaporators?

Answer 9

True

Question 10

Captube metering devices are most often used with which compressors?

Answer 10

RSIR

Question 11

A thermostatic expansion valve type C is good for what evaporator temperature range?

Answer 11

50 to -10F

Question 12

A TXV with a liquid charge power element has ?

Answer 12

Ability to prevent bulb charge migration

Question 13

The main function for any metering device is to

Answer 13

Provide a pressure drop

Question 14

Why would an undercharged high side float possibly starve the evaporator ?

Answer 14

Not enough refrigerant in the system to fill the condenser to the high level which opens the valve or solenoid to allow liquid to enter the chiller. ( evaporator)

Question 15

Why would in some captube systems the cap tube is brazed to the suction line and covered with armour flex insulation? What is the purpose of this?

Answer 15

To extend the bubble point in a cap tube and also add system superheat.

Question 16

A TXV with an X charge is good for what temperature range?

Answer 16

-40 to -100F

Question 17

Cap tube systems are typically used with which component ?

Answer 17

Accumulator

Question 18

The AEV spring set to maintains a saturated suction pressure and the valve opens and closes on ?

Answer 18

Evaporator pressure

Question 19

The first symptom of an overcharged high side float is?

Answer 19

Overfilled evaporator and possible flood back to compressor

Question 20

An externally charged TXV must be used when 2 criteria is met?

Answer 20

A distributer is used and pressure drop across the evaporator is greater then 2F

Question 21

The AEV would most likely be used in ?

Answer 21

Constant load applications , like a slurpy machine

Question 22

What are advantages of a cap tube system ?

Answer 22

They are cheep and no moving parts.

Question 23

What are TXV rated by?

Answer 23

Tons

Question 24

An externally equalized TXV does it equalize quickly in the off cycle?

Answer 24

No

Question 25

If the spring in a TXV lost tension over time, what would you expect your superheat value to be?

Answer 25

Less superheat

Question 26

Purpose of a high side float ?

Answer 26

Open a valve or energize a solenoid valve when the level of liquid in the condenser reaches its high level.

Question 27

What is the minimum and maximum length of cap tube?

Answer 27

6 ft to 18 ft

Question 28

If the bulb of a TXV is not tightly strapped and insulated to the suction line and the box temp is warmer then suction line, the valve will tend to ?

Answer 28

Over feed

Question 29

An overcharged low side float system will experience which symptoms?

Answer 29

High discharge pressure.