313D Review Exam (complete) Flashcards
“The X terminal on a defrost time clock is used for?”
A:Termintating the Defrost cycle
B:Energizing the defrost heater
C:De-energizing the condensing unit
D:Energizing the Evap Fan
A:Terminating the defrost cycle
‘X’ gets power when the thermostat reaches 55F, ending the defrost early
“Cylinder color code for r502 is?”
1. Pink
2. White
3. Purple
4. Green
3:Purple!
“Cylinder Color Code for R12 is?:
1. White
2. Green
3. Pink
4. Purple
1:White!
In a pure Resistive Circuit,
1. Voltage leads Current
2. Current leads Voltage
3. Current and Voltage are in phase
3:Current and Voltage are in phase.
In a pure Capacitive circuit
1. Voltage Leads Current by 90 Deg
2. Current and Voltage are in Phase
3. Current Leads Voltage by 90 Deg
3:Curret Leads Voltage by 90 deg
In a purely inductive circuit;
1. Current and Voltage are in phase
2. Voltage leads Current, by 90 Deg.
3. Current leads Voltage, by 90 Deg.
2.Voltage leads Current,by 90 Deg.
What would be the result be if you installed an externally equalized txv but did not hook up the external equalized but did not hook up the external equalized line?
1. Flooded evaporator coil
2. Starved evaporator coil
3. No effect on system capacity
4. Equalized line does not need to be hooked up
Flooded Evaporator Coil
If there was Nitrogen left in a system due to poor installation practice, what effect will this have on operating pressure?
1. Normal Operating Pressure
2. Lower Head Pressure, slightly higher suction pressure
3. Lower head pressure, slighlty lower suction pressure
4. Higher head pressure, normal to higher suction pressure
Higher head pressure, normal to higher suction pressure
A shortage of refrigerant in a system will result in?
1. High Superheat
2. Low Superheat
3. Decrease in discharge temperature
4. Increase in subcooling
High Superheat
Replacing an internally equalized txv with an externally equalized TXV will result in?
1. No change in superheat
2. Reduced superheat
3. Increased Superheat
No change in superheat!
Replacing an externally equalized TXV with an internally equalized TXV will result in?
1. No change in superheat
2. Reduced superheat
3. Increased superheat
Increased Superheat
When replacing an externally equalized TXV with an Internally equalized TXV, what will the effect on the cooling capacity be?
1. No effect on capacity
2. Reduced cooling capacity
3. Increased cooling capacity
Reduced Cooling capacity
When replacing an Internally equalized TXV with an Externally equalized TXV, what will the effect on the cooling capacity be?
1. No effect on capacity
2. Reduced cooling capacity
3. Increased cooling capacity
No effect on capacity
A dirty condenser coil will result in?
1. High compression ratio
2. Normal compression ratio
3. Low compression ratio
4. No effect on compression ratio
High compression ratio
When does liquid start to form in the condenser?
1. After the subcooling has been removed
2. After all the refrigerant gains sufficient superheat
3. After the refrigerant has gained enough subcooling
4. After the refrigerant has desuperheated
After the refrigerant has desuperheated
Three compressor types, physcal enclosures
1. Semi Hermatic, Hermatic, Open drive
2. Front Incline Enclouse, hermatic open drive, backwards incline enclosure
3. Semi Hermatic, Hermatic, Backwards incline enclosure
4. Semi open drive, Open drive, hermatic
Semi Hermatic, Hermatic, Open drive
What is a refrigerant blend?
Mixture of refrigerants that readily mix together
What is an Azeotropic Refrigerant?
Two or more refrigerant mixed together that have the combined properties of a single refrigerant
What is the problem when you arrive at a R410A and the System is really low on refrigerant.
Problem is Fractionation, what is left in the system is not pure 410A
The Replacement refrigerant for R134A is?
Propane
Cylinder Colour for R134A is
Light Blue
Cylinder Colour for R404A is?
Orange
Cylinder colour code for R410A is?
Pink
Cylinder colour for R22?
Green
If we have a long vertical liquid line rise, what is it important to make sure we have sufficient amount of?
Subcooled refrigerant
What is the normal compression ratio for central AC?
3:1
Compression Ratio is?
Absolute discharge pressure divided by absolute suction pressure
The volumetric efficiency decreases with an increase of ?
Discharge Pressure
If the maximum suction line temp is exceeded what result would it have on the compressor operation?
Compressor will eventually stop because of internal overload
If the maximum discharge temp is exceeded what is the result?
Compressor oil will break down
What is the maximum allowable temp of the compressor discharge line?
225
To increase superheat on a TXV we turn the adjustment stem?
Clockwise
To decrease the suction pressure we turn the AXV(AEV) stem?
Counter-Clockwise
To increase suction pressure we turn the AEV(AXV) stem?
Clockwise
During high heat loads the automatic expansion valve will____ the evaporator?
Starve
During low heat loads the automatic expansion valve will____ the evaporator?
Flood
An automatic expansion valve maintains a constant?
Suction pressure
