Evaporator Feed Controls Flashcards
Electronic expansion devices are able to operate near 0F ?
Yes, and they do not have a sensing bulb
If the capillary tube is plugged in the first 6 inches it’s most likely to have what?
Drier desiccant, dirt or copper filings
When pressures are equal in AEV ?
Spring pressure = evaporator pressure or p1=p2
Z charge temperature range is?
0F to -40F
Vapour in the liquid line will dramatically reduce the capacity of TXV?
Yes it’s true
A TXV is said to be balanced when P1=P2+P3. Bulb pressure (opening)= evaporator pressure (SSP)(closing)+ spring force (superheat)(closing)
True
Sizing a capillary tube is done by?
Using inside diameter and length.
An undercharge cap tube system would have symptoms of ?
Low suction pressure
Low discharge pressure
Low amp draw
High superheat
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?
True
Captube metering devices are most often used with which compressors?
RSIR
A thermostatic expansion valve type C is good for what evaporator temperature range?
50 to -10F
A TXV with a liquid charge power element has ?
Ability to prevent bulb charge migration
The main function for any metering device is to
Provide a pressure drop
Why would an undercharged high side float possibly starve the evaporator ?
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)
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?
To extend the bubble point in a cap tube and also add system superheat.
A TXV with an X charge is good for what temperature range?
-40 to -100F
Cap tube systems are typically used with which component ?
Accumulator
The AEV spring set to maintains a saturated suction pressure and the valve opens and closes on ?
Evaporator pressure
The first symptom of an overcharged high side float is?
Overfilled evaporator and possible flood back to compressor
An externally charged TXV must be used when 2 criteria is met?
A distributer is used and pressure drop across the evaporator is greater then 2F
The AEV would most likely be used in ?
Constant load applications , like a slurpy machine
What are advantages of a cap tube system ?
They are cheep and no moving parts.
What are TXV rated by?
Tons
An externally equalized TXV does it equalize quickly in the off cycle?
No
If the spring in a TXV lost tension over time, what would you expect your superheat value to be?
Less superheat
Purpose of a high side float ?
Open a valve or energize a solenoid valve when the level of liquid in the condenser reaches its high level.
What is the minimum and maximum length of cap tube?
6 ft to 18 ft
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 ?
Over feed
An overcharged low side float system will experience which symptoms?
High discharge pressure.
