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Refrigeration 3rd Yr > Finals Review > Flashcards

Finals Review Flashcards

1
Q

Superheat Calculation

A

Suction line temp - SST

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2
Q

Subcooling Calculation

A

SDT - Liquid Line Temp

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3
Q

Evaporator Superheat - Where to take temp?

A

Outlet of the evaporator

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4
Q

System Superheat - Where to take the temp?

A

4-6” from inlet of compressor

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5
Q

Condenser Subcooling - Where to take the temp?

A

Measured at the outlet of the condenser

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6
Q

System Subcooling - Where to take the temp?

A

Inlet of the TXV (Metering Device)

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7
Q

Evaporator T.D

A

SST - Return Air

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8
Q

Evaporator Delta T

A

Return Air - Supply Air

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9
Q

Condenser Temperature Rise

A

Air Entering Condenser - Air Leaving Condenser

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10
Q

Condenser Split

A

Entering Air - SDT

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11
Q

Compressor Vibration Absorbers are used

A

Semi-Hermetics

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12
Q

Receivers can’t be lower than __% full

A

10%

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13
Q

Components that can not be used on capillary tube systems

A

Receiver

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14
Q

Filter Drier: Activated Alumina

A

High Acid, moderate moisture (Compressor Burnout)

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15
Q

Filter Drier: Molecular Sieve

A

Low Acid, High Moisture

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16
Q

Filter Drier: Silica Gel

A

High Moisture

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17
Q

Acceptable temp drop across a Filter Drier

A

2 F

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18
Q

Direct Acting Solenoid Valve

A

Used in low flow/ pressure differential across valve

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19
Q

Pilot Operated Solenoid Valve

A

Uses system pressure to keep open & close

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20
Q

Most efficient type of Evaporator

A

Liquid Overfeed

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21
Q

Least Efficient type of Evaporator

A

DX Coil

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22
Q

On multi-evaporator systems, which would require an EPR valve

A

All but the coldest

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23
Q

When is a suction line solenoid valve used?

A

-To protect against undershoot
-Systems with long runs/evaps
-Re-Evaporator Systems

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24
Q

How to size a Accumulator

A

Capacity + Tonnage

25
What does a CPR protect against?
High load situations = High current draw due to High Suction Pressure
26
High Pressure safety cut out temperature?
130 F
27
Insulation Wall Thickness for different applications
HVAC/ Residential = 3/8" Coolers = 1/2" Freezers = 3/4"
28
Why use an unloader?
Keep Suction pressure up, T.D. up means less frost build-up
29
Suction-Cut off Unloader
cuts gas from entering the cylinder on the suction side
30
Hydraulic unloaders use what pressure to unload?
Oil Pressure
31
A de-energized oil port solenoid in a hydraulic unloader means the compressor is loaded or unloaded
unloaded
32
Purpose of a Lock-out Relay
Requires the triggering of a safety to be manually reset.
33
Lock-out Relays have 1 set of NO or NC contacts
NC
34
This defrost initiation requires a time clock and is most reliable
Time Initiated
35
this defrost initiation tracks compressor run time and is used in residential applications
Run Time initiated
36
This defrost initiation initiates when required and is MOST energy efficient
On-Demand
37
Defrost initiation that's only used on off-cycle defrost applications
Pressure/ Temperature Initiated
38
Most common type of defrost termination
Temperature Terminated
39
4 Main types of defrosts
1. Supplemental Heat Defrost 2. Natural Defrost 3. Frost Removal 4. Manuel Shutdown
40
Recovery Time
The period right after refrigeration starts following a defrost.
41
Most common method of defosting in blast freezers/coolers
Hot Gas Defrost
42
On hot gas defrost the condenser fan motor is energized/de-energized?
de-energized: Tt keep head pressure up
43
Type of vapour defrost that runs out of heat quickly into the defrost cycle
3 pipe conventional flow
44
What is conventional flow mean
Refrigerant flows in the same direction during cooling and defrosting
45
Cons of 3 pipe conventional flow
1. 3rd pipes expensive 2. Damages pipe due to thermal shock
46
3 pipe conventional flow with re-evaporator has a SLSV. Is it open or closed during the main evaporators cooling cycle?
Energized to prevent excessive pressure drop
47
Reversing Cycle Defrost requires what other component?
Reversing Valve
48
Is the Reversing Cycle a conventional flow system
Nah mate
49
2 Pipe Reverse Flow requires what special valves
1. Defrost Pressure Regulating Valve 2. 3 way solenoid Valve
50
Defrost Pressure Regulating Valve is energized/de-energized during a defrost call?
De-Energized to create the pressure differential
51
On a Natural Defrost Off Cycle Pressure Operated, every time the LPC contacts open, the system is in a...
Defrost
52
most common combination of defrost initiation/termination for commercial freezer application?
Time in - Temp Out
53
When measuring a compressor discharge temperature. How much higher is it expected to be 6" away
50-75 F
54
A perfect storm of moisture, heat and acidity can cause...
Copper Plating
55
Higher discharge or Lower suction will more greatly affect the compression ratio?
Lower Suction
56
How will floodback on a suction cooled compressor present itself?
Damage to the crankshaft will get progressively less as per oil flow
57
Floodback on an air-cooled compressor will present itself as?
Damage at the cylinder
58
What condition will cause erratic damage inside the compressor
Flooded Start
59
Cap tues can not handle more than __% overcharge
10%

Refrigeration 3rd Yr (2 decks)

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