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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
Q

What does a CPR protect against?

A

High load situations = High current draw due to High Suction Pressure

26
Q

High Pressure safety cut out temperature?

A

130 F

27
Q

Insulation Wall Thickness for different applications

A

HVAC/ Residential = 3/8”
Coolers = 1/2”
Freezers = 3/4”

28
Q

Why use an unloader?

A

Keep Suction pressure up, T.D. up means less frost build-up

29
Q

Suction-Cut off Unloader

A

cuts gas from entering the cylinder on the suction side

30
Q

Hydraulic unloaders use what pressure to unload?

A

Oil Pressure

31
Q

A de-energized oil port solenoid in a hydraulic unloader means the compressor is loaded or unloaded

A

unloaded

32
Q

Purpose of a Lock-out Relay

A

Requires the triggering of a safety to be manually reset.

33
Q

Lock-out Relays have 1 set of NO or NC contacts

A

NC

34
Q

This defrost initiation requires a time clock and is most reliable

A

Time Initiated

35
Q

this defrost initiation tracks compressor run time and is used in residential applications

A

Run Time initiated

36
Q

This defrost initiation initiates when required and is MOST energy efficient

A

On-Demand

37
Q

Defrost initiation that’s only used on off-cycle defrost applications

A

Pressure/ Temperature Initiated

38
Q

Most common type of defrost termination

A

Temperature Terminated

39
Q

4 Main types of defrosts

A
  1. Supplemental Heat Defrost
  2. Natural Defrost
  3. Frost Removal
  4. Manuel Shutdown
40
Q

Recovery Time

A

The period right after refrigeration starts following a defrost.

41
Q

Most common method of defosting in blast freezers/coolers

A

Hot Gas Defrost

42
Q

On hot gas defrost the condenser fan motor is energized/de-energized?

A

de-energized: Tt keep head pressure up

43
Q

Type of vapour defrost that runs out of heat quickly into the defrost cycle

A

3 pipe conventional flow

44
Q

What is conventional flow mean

A

Refrigerant flows in the same direction during cooling and defrosting

45
Q

Cons of 3 pipe conventional flow

A
  1. 3rd pipes expensive
  2. Damages pipe due to thermal shock
46
Q

3 pipe conventional flow with re-evaporator has a SLSV. Is it open or closed during the main evaporators cooling cycle?

A

Energized to prevent excessive pressure drop

47
Q

Reversing Cycle Defrost requires what other component?

A

Reversing Valve

48
Q

Is the Reversing Cycle a conventional flow system

A

Nah mate

49
Q

2 Pipe Reverse Flow requires what special valves

A
  1. Defrost Pressure Regulating Valve
  2. 3 way solenoid Valve
50
Q

Defrost Pressure Regulating Valve is energized/de-energized during a defrost call?

A

De-Energized to create the pressure differential

51
Q

On a Natural Defrost Off Cycle Pressure Operated, every time the LPC contacts open, the system is in a…

A

Defrost

52
Q

most common combination of defrost initiation/termination for commercial freezer application?

A

Time in - Temp Out

53
Q

When measuring a compressor discharge temperature. How much higher is it expected to be 6” away

A

50-75 F

54
Q

A perfect storm of moisture, heat and acidity can cause…

A

Copper Plating

55
Q

Higher discharge or Lower suction will more greatly affect the compression ratio?

A

Lower Suction

56
Q

How will floodback on a suction cooled compressor present itself?

A

Damage to the crankshaft will get progressively less as per oil flow

57
Q

Floodback on an air-cooled compressor will present itself as?

A

Damage at the cylinder

58
Q

What condition will cause erratic damage inside the compressor

A

Flooded Start

59
Q

Cap tues can not handle more than __% overcharge

A

10%

Refrigeration 3rd Yr (2 decks)

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