313D Review Exam (complete) Flashcards

Review Exams

1
Q

“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

A:Terminating the defrost cycle

‘X’ gets power when the thermostat reaches 55F, ending the defrost early

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2
Q

“Cylinder color code for r502 is?”
1. Pink
2. White
3. Purple
4. Green

A

3:Purple!

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3
Q

“Cylinder Color Code for R12 is?:
1. White
2. Green
3. Pink
4. Purple

A

1:White!

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4
Q

In a pure Resistive Circuit,
1. Voltage leads Current
2. Current leads Voltage
3. Current and Voltage are in phase

A

3:Current and Voltage are in phase.

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5
Q

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

A

3:Curret Leads Voltage by 90 deg

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6
Q

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.

A

2.Voltage leads Current,by 90 Deg.

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7
Q

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

A

Flooded Evaporator Coil

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8
Q

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

A

Higher head pressure, normal to higher suction pressure

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9
Q

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

A

High Superheat

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10
Q

Replacing an internally equalized txv with an externally equalized TXV will result in?
1. No change in superheat
2. Reduced superheat
3. Increased Superheat

A

No change in superheat!

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11
Q

Replacing an externally equalized TXV with an internally equalized TXV will result in?
1. No change in superheat
2. Reduced superheat
3. Increased superheat

A

Increased Superheat

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12
Q

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

A

Reduced Cooling capacity

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13
Q

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

A

No effect on capacity

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14
Q

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

A

High compression ratio

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15
Q

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

A

After the refrigerant has desuperheated

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16
Q

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

A

Semi Hermatic, Hermatic, Open drive

17
Q

What is a refrigerant blend?

A

Mixture of refrigerants that readily mix together

18
Q

What is an Azeotropic Refrigerant?

A

Two or more refrigerant mixed together that have the combined properties of a single refrigerant

19
Q

What is the problem when you arrive at a R410A and the System is really low on refrigerant.

A

Problem is Fractionation, what is left in the system is not pure 410A

20
Q

The Replacement refrigerant for R134A is?

A

Propane

21
Q

Cylinder Colour for R134A is

A

Light Blue

22
Q

Cylinder Colour for R404A is?

A

Orange

23
Q

Cylinder colour code for R410A is?

A

Pink

24
Q

Cylinder colour for R22?

A

Green

25
Q

If we have a long vertical liquid line rise, what is it important to make sure we have sufficient amount of?

A

Subcooled refrigerant

26
Q

What is the normal compression ratio for central AC?

A

3:1

27
Q

Compression Ratio is?

A

Absolute discharge pressure divided by absolute suction pressure

28
Q

The volumetric efficiency decreases with an increase of ?

A

Discharge Pressure

29
Q

If the maximum suction line temp is exceeded what result would it have on the compressor operation?

A

Compressor will eventually stop because of internal overload

30
Q

If the maximum discharge temp is exceeded what is the result?

A

Compressor oil will break down

31
Q

What is the maximum allowable temp of the compressor discharge line?

A

225

32
Q

To increase superheat on a TXV we turn the adjustment stem?

A

Clockwise

33
Q

To decrease the suction pressure we turn the AXV(AEV) stem?

A

Counter-Clockwise

34
Q

To increase suction pressure we turn the AEV(AXV) stem?

A

Clockwise

35
Q

During high heat loads the automatic expansion valve will____ the evaporator?

A

Starve

36
Q

During low heat loads the automatic expansion valve will____ the evaporator?

A

Flood

37
Q

An automatic expansion valve maintains a constant?

A

Suction pressure