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Unit 22 > Unit 22 Quiz > Flashcards

Unit 22 Quiz Flashcards

1
Q

Coil of tubing packed into a shell and then closed and welded.

A

Shell and coil

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2
Q

Water in the inner tube removes heat from the refrigerant in the outer tube.

A

Tube-within-a-tube coil

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3
Q

System where water is used over and over such as chilled water or cooling tower system.

A

Recirculated water system

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4
Q

A water cooling tower that has a fan on the side of the tower that pushes air through the tower as opposed to an induced draft tower.

A

Forced draft tower

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5
Q

Rejects heat absorbed into the system from the evaporator.

A

Condenser

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6
Q

Water used once and then wasted down the drain.

A

Waste water system

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7
Q

Turns a condenser fan on and off to maintain a correct pressure within the system.

A

Fan cycling

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8
Q

Most expensive condenser but can be cleaned mechanically with brushes. Straight copper tubes fastened into an end sheet within a steel shell.

A

Shell and tube

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9
Q

Located at the inlet or outlet to condenser. Used to control head pressure.

A

Air damper

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10
Q

Removing heat from the superheated hot refrigerant gas down to the condensing temperature.

A

Desuperheating

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11
Q

One half used for winter operation and both halves used for summer operation.

A

Condenser splitting

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12
Q

What state is the refrigerant in when it leaves the condenser?

A

High pressure high temp liquid

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13
Q

Where is the evaporative condenser located?

A

Inside the cooling tower

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14
Q

What is the purpose of condenser flooding?

A

To keep pressure up inside the condenser
so that the correct amount of refrigerant
Reaches the metering device.

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15
Q

What are five ways to control head pressure?

A
  1. Dampers
  2. Condenser flooding
  3. VFD
    4.Condenser splitting
  4. Fan cycling controls
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16
Q

A high efficiency condenser coil operating with an ambient temperature of 95 F will condense refrigerant at what temperature?

A

95F + 15F = 110F

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17
Q

A cooling tower can be constructed with different types of fill material used to help cool the water. What are three types of fill material that can be used?

A

Redwood, Fiberglass, Plastic

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18
Q

Condensers can be air cooled or water cooled. What are three condenser configurations for a water cooled condenser?

A

Shell in tube, shell in coil, tube in tube

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19
Q

A water pressure regulating valve for a water-cooled condenser works like a thermal expansion valve (TXV). As head pressure increases, the water valve will ______ water flow through the condenser to keep the head pressure correct.

A

Increase

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20
Q

How is mineral buildup in the evaporative condenser controlled without using chemicals?

A

Blow down

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21
Q

Water boxes refer to _______.

A

The end caps of the shell and tube condenser

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22
Q

Water used to cool condensers can either be _______ or __________.

A

Wasted, recycled

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23
Q

Where is the ORI valve placed in the system and what does it do?

A
  1. Outlet of condenser/inlet of receiver
  2. Regulates pressures in the condenser
  3. Opens to relieve pressure when the set point is exceeded
24
Q

The outdoor condensing unit that uses R-410A refrigerant should have a subcooling value of 10 degrees. The high side manifold gauge reads 317 psig. You place a thermocouple at the exit of the condenser to measure the temperature. What temperature would indicate the unit is properly charged with the correct amount of refrigerant?

A

100F -10F =90F

25
Q

True or false: The ORD valve can be adjusted.

A

False

26
Q

True or false: As the ORI valve throttles down, the ORD valve will open to keep the receiver at the proper pressure to supply liquid refrigerant to the metering device.

A

True

27
Q

True or false: A condensing unit that measures low subcooling has too much refrigerant.

A

False

28
Q

True or false: A low subcooling number could also mean the condenser is dirty.

A

True

29
Q

True or false: When measuring condenser subcooling for commercial and industrial applications, the pressure must be read close to the condenser outlet, not at the compressor service valve.

A

True

30
Q

True or false: For an air-cooled condenser, the refrigerant inside the condenser coil will begin to condense at a temperature 30 degrees higher than the air passing over the coil (also known as ambient air).

A

True

31
Q

True or false: Ambient air temp moving across a regular fin and tube condenser coil is 95F for a unit using R-22 refrigerant. The pressure inside the condenser that the refrigerant is starting to condense at is 278 psig.

A

True

32
Q

True or false: Charging a unit that has a dirty condenser coil will not affect subcooling.

A

False

33
Q

True or false: Hot gas enters the condenser from the bottom of the condenser.

A

False

34
Q

True or false: The shell-and-coil and tube-in-tube condensers can only remove mineral buildup by using chemicals.

A

True

35
Q

True or false: Natural draft cooling towers can be negatively affected if prevailing winds cannot blow through it.

A

True

36
Q

True or false: The Low Ambient Control (LAC) valve is a combination of the ORI and ORD valve.

A

True

37
Q

True or false: Shell type condensers (shell-and-tube & shell-and-coil) are also used as a receiver to hold the entire refrigerant charge of the system.

A

True

38
Q

As the ____ valve is throttling closed, the _____ valve is opening to allow pressure in the receiver to maintain proper receiver pressure, regardless of the outside ambient conditions.

A

ORI, ORD

39
Q

What would be the result if an air-cooled condenser had two fans and one stopped running?

A

Over heating and high head pressures will occur

40
Q

What methods are used to prevent the water in the cooling tower from freezing during the winter?

A

Anti-freeze chemical solution can be placed in the water, adding a heater, bubble acrotor

41
Q

As voltage frequency _____ in a variable frequency drive fan motor, the motor speed ______.

A

Increases, Increases

42
Q

Explain three ways water can be lost in a cooling tower.

A

Leaking valves
evaporation
high winds

43
Q

Where is the ORD valve installed and what does it do?

A

Hot gas line & Inlet of Receiver.
Provides proper pressure for the receiver
in order to supply liquid refrigerant
to the metering device
when ORI valve is closed off

44
Q

Use the diagram to draw in the location of the ORI and ORD valves.

A
45
Q

If the spring pressure of a water regulating valve is increased, the system head pressure will _________.

A

Increase

46
Q

In a tube-within-a-tube condenser, the refrigerant flows in the ______ tube and the water flows in the ______ tube.

A

Outer, Inner

47
Q

What is the condenser saturation temperature if there is 20F of subcooling and the outlet temperature of the condenser is 90F?

A

90F + 20F = 110F

48
Q

In order for a flooded condenser type head pressure control system to operate, what device/component holds the extra refrigerant in warmer weather when the condenser doesn’t need to be flooded.

A

Receiver

49
Q

A normally operating water cooled condenser is operating with a 10 degrees differential between water in and water out. If scale forms on the water tubes and the entering water is 85F, which of the following is possible?

A

Both a & b are correct

A. The outlet water temperature will be lower than expected.

B. The system head pressure will rise

50
Q

How does the inverter on a VFD drive know when to speed up or slow down the condenser fan on a cooling tower?

A

The Sensors send signals in regards to temperature to the VFD drive to either slow down or speed up the condenser fan

51
Q

Name four tasks that need to be checked when performing preventive maintenance on cooling towers.

A

Water pressure
Water meter
Water regulating valve
Float valve

52
Q

Where does refrigerant vapor condense in a typical condenser?

A

Middle

53
Q

What happens in the switching section of a variable speed motor drive controller?

A

Changes DC to AC

54
Q

To measure the coil resistance on a current relay, what terminals would you put your test probes on?

A

L & M

55
Q

There are four shapes used to increase the amount of warp for a bimetal device. What are tow shapes that can be used?

A

Helix & Hairpin

Unit 22 (1 decks)

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