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3rd Year Refrig Sait 2019 > Dom Class > Flashcards

Dom Class Flashcards

1
Q

Vibersorbers installed…

A
  • Parallel to crankshaft,
  • highest probability of leak location
  • Not used on hermetic compressors
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2
Q

Receiver charge

A

Must hold 90% of charge at 90F

Minimum 10% full at any time

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3
Q

Winter charge

A

Additional charge for receivers due to low ambient condition

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4
Q

Heat pump filter driers

A

Special non directional

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5
Q

Filter drier Sight glass location

A

Immediately after filter drier to indicate full column of liquid. Especially when evap is at higher elevation than condensor

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6
Q

LLSV always after filter drier, why?

A

Keeps filter drier on high side, prevents impurities from escaping during pump down

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7
Q

Txv outlet position

A

Always up

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8
Q

What type of txv is needed to eliminate the need for a CPR

A

Pressure limiting txv

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9
Q

Where to discharge air on pull through evaporator

A

Towards opening to prevent air infiltration

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10
Q

Another name for push through evaporator and location

A 
Low velocity, center of room
HIGH HUMIDITY (flowers)
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11
Q

Suction line solenoids, location, application and purpose

A

After EPR, large case with critical set points, used to avoid excessive pressure drops

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12
Q

Accumulator location and and sizing

A

Close as possible to inlet. Sized based on tonnage of system

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13
Q

When should you insulate Accumulators

A

Outdoors only, intent is to boil off remaining liquid refrigerant, insulated indoor could prevent this

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14
Q

CPR location

A

Close as possible to compressor after accumulator

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15
Q

Max temp before damage to compressor occurs

A

135F

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16
Q

Head pressure control methods (3)

A

Fan cycling
Fan speed control
Condensor flooding

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17
Q

Fan cycling monitors what and is most used on what system

A

Monitors discharge pressure or temperature

Most used on cap tube system

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18
Q

Two types of fan speed controls

A

VFD and ECM motors

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19
Q

Insulation thickness for freezer

A

3/4 or greater

Dom test said 5/8

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20
Q

Insulation thickness for cooler

A

1/2 inch or greater

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21
Q

High temp ac insulation thickness

A

3/8” or greater

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22
Q

Copeland unloading

A 
Suction port is
C OPE(n)lan D(energized)
Unloading 
Copeland uses discharge as closing force
Copelan(D)
Carlyle uses electromagnet to close valves
Carlyl(E)
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23
Q

Suction lift unloading

A

Coil energized, oil pressure lifts lever, loads compressor cylinder
Uses oil pump

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24
Q

Ideal evap Temperature Difference

A

8-10F

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25
Q

Importance of proper evap TD

A

Too high = frost build up

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26
Q

Easiest method of defrost

A

Manual defrost

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27
Q

Types of defrost methods (5 types)

A

Manual frost removal
Manual defrost
Off cycle defrost
Timed shut down

SUPPLEMENTARY DEFROST
Water defrost
Brine spray defrost
Electric defrost
Vapor defrost
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28
Q

Temperature operated defrost setting

A

35F cut it, 22F cut out

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29
Q

Accumulator sizing during hot gas bypass conventional flow (3 pipe system)

A

1.5 times system

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30
Q

3 pipe HGBP with re evaporator

Suction line Solenoid position and purpose during normal operation

A

Open to prevent excessive pressure drop

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31
Q

Max temp difference across 4 way valve

A

5F

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32
Q

Purpose of DPRV

A

Maintain pressure difference to ensure flow of refrigerant

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33
Q

Fin spacing colder vs warmer evap

A

Wider in colder

Closer on warmer

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34
Q

Manual frost removal equipment status

A

Running

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35
Q

Cooler application evap fan run time

A

24hrs

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36
Q

Another name for EPR

A

ORI

Open on rise of inlet

37
Q

Hot gas bypass line connects at where

A

Between txv and evap

38
Q

Grocery rack check valve location in relation to LLSV and purpose

A

Parallel, to send liquid back to liquid receiver during defrost cycle

39
Q

Ammonia chemical make up and refrigerant designation

A

R-717
B2
NH4

40
Q

Water refrigerant designation

A

R-718

41
Q

Propane refrigerant designation

A

R-290

A3

42
Q

R404a classification

A

A1

43
Q

Pressure test duration and oxygen content

A

2 hour minimum, no more than 20%

44
Q

Pressure relief valve rates by

A

Psi dry air

45
Q

Above 400 lbs A1 (ammonia) or 200 lbs of all other refrigerants at 15 psi requires what

A

Relief to atmosphere (ammonia)

46
Q 
Restricted air flow causes what to the following
Suction pressure
Super heat
Subcooling
Compressor amperage
A

Decreased Suction pressure
Decreased Super heat
Decreased Subcooling
Decreased Compressor amperage

47
Q

What happens to system if defrost cycle times out but doesn’t reach temperature

A

Defrost continues until DTS set point is reached then Pushes pin to end Defrost cycle

48
Q

Define floodback

A

Liquid fed to compressor DURING cooling operation

49
Q

Define flooded start

A

Liquid foaming on top of oil at start

50
Q

Define slugging

A

Liquid in evap forced in to compressor at start (snot rocket)

51
Q

Which ice contains impurities

A

Flake ice, used on foods

52
Q

Purpose of harvest clutch

A

To detect when ice has fully separated from evap, NOT TO PUSH IT OFF

53
Q

Water inlet pressure on ice machine

A

20-80 psi

54
Q

50-75% of ice machine problems are what

A

Water related (dirty, pressure, drainage)

55
Q

Ice machine condensor water temp

A

95-105F

56
Q

Ice daily production formula

A

(1440 minutes/ cycle time) x weight of ice = daily production

57
Q

How much ammonia is deadly in 10x10x10 room

A

1 tablespoon

58
Q

Ammonia system capacity required for one skating rink

A

100 tons of cooling

59
Q

3 best refrigerants in order

A

Water
Ammonia
Co2

60
Q

All ammonia system requires what component

A

Oil separator
Oil cannot be reused
Once it leaves separator it does not return

61
Q

Other names for tell tale

A

Oil pot and drop leg

Where oil collects at bottom of system

62
Q

Water required to neutralize ammonia

A

10:1

63
Q

Purpose of surge drum

A

To eliminate carry over of liquid ammonia to compressor. Suction line sloped 1/2” per 10 ft

64
Q

Ammonia fire line requirements

A

Vent 25’ away from openings to building

Fire fighter valve located outdoors in red box 7’ above ground

65
Q

Screw compressor max pressure

A

350 psi

66
Q

Screw compressor parts

A

Male lobe, female flute

67
Q

Screw compressor application

A

Air, gas, refrigerant, and natural gas processing

68
Q

Ammonia recip compressor cooling

A

External

69
Q

Ammonia oil cooled to what temp

A

120F

140F (bill)

70
Q

Screw compressor unloading capability

A

Down to 10% capacity

71
Q

Screw compressor compression ratio

A

2:1 to 20:1

72
Q

Most efficient /least efficient ammonia evaporator

A

Liquid overfead/ DX coil

73
Q

Screw compressor unloading force

A

Hydraulic, oil pump

74
Q

TLV/TWA definition and application

A

Threshold limit value/ time weighted average

Refrigerant exposure effects during normal average work week

75
Q

Pressure limiting vs pressure relief

A

Stop operation vs disposal of excess pressures

76
Q

Occupational classification minimum distance to prevent grouping togeather

A

20ft

77
Q

Safety group
A-B
1-3

A

Toxicity lowest to highest

Flammability lowest to highest

78
Q

Stairwells

A

NO INSTALLATIONS EVER

79
Q

Max size soft copper

A

1 3/8”

80
Q

Permanently installed pressure guage rating

A

1.2 times design pressure (not operating pressure)

81
Q

4 major location requirements of refrigeration equipment

A

1) permanent installed stair or ladder
2) sufficient clearance
3) 10 ft back from all edges (6 ft in ???)
4) if mobile equipment required, always on site and ready

82
Q

Maximum amount of refrigerant in storage

A

300 lbs

83
Q

Easy repair on compressor

A

Oil change and valve plate

84
Q

Maximum compressor discharge temp

A

300F

85
Q

Txv power element = ____ force

A

Opening
Severed bulb = closed shut
Pinched line = wide open or one setting (acts like hand expansion valve)

86
Q

“Nominal” super heat settings

A 
Ac = 15F
Cooler = 10F
Freezer = 5F
87
Q

Nominal Condensing temp

A

30F above ambient

88
Q

Oil breakdown temp

A

350F

89
Q

Oil no longer lubricates at what temp

A

300-320

3rd Year Refrig Sait 2019 (5 decks)

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