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Chief Study Guide > HVAC > Flashcards

HVAC Flashcards

1
Q

What would you expect to happen to a chiller if the only condenser water pump failed and the flow switch failed also?

A

Chiller would trip on high pressure.

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2
Q

In what state is the refrigerant just after the compressor but before the condenser?

A

Hot gas

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3
Q

Why is blow-down needed on a condenser water circuit?

A

To eliminate dissolved solids from the water.

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4
Q

What is the purpose of an expansion tank on a closed water loop?

A

To allow for thermal expansion

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5
Q

What is a possible cause of an evaporator coil becoming iced?

A

Low refrigerant charge or low airflow.

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6
Q

What would you expect to happen to a chiller if the only chilled water pump failed and the flow switch failed also?

A

Chiller would trip on low pressure or low temp.

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7
Q

Why is the oil kept warm in an off-line chiller?

A

To prevent the migration of refrigerant into the oil.

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8
Q

What is the purpose of the metering device in a refrigeration circuit?

A

To allow pressure drop to the evaporator.

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9
Q

What happens to the efficiency of a cooling tower on a very humid day? Why?

A

Decreases, evaporation is not as efficient.

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10
Q

What is chiller approach?

A

Tells you the efficiency of your chiller

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11
Q

What would cause a high “small temperature difference” (approach)?

A

Fouled tubes

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12
Q

What is Eddy Current Testing?

A

Uses electromagnetic induction to detect flaws in the chiller tubes

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13
Q

How is a capacitor measured?

A

Farad

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14
Q

What type of chiller would you see a purge unit on and what is it used for?

A

Low pressure chiller. It removes air from the system that may have been brought in from a leak in the chiller’s refrigerant system.

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15
Q

What is CFM and what is it used for?

A

Cubic Feet per Minute. Measures air flow.

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16
Q

Name the four major components of a refrigerant circuit.

A

Compressor, condenser, expansion device and evaporator.

17
Q

What does BTU stand for and what is a BTU?

A

British thermal unit. The amount of energy needed to raise one pound of water one degree Fahrenheit.

18
Q

How many BTUs are in one ton of refrigeration?

A

12,000 BTU

19
Q

Name at least three different types of refrigeration compressors.

A

Reciprocating, centrifugal, screw, etc…

20
Q

What is superheat? As it relates to a refrigerant circuit.

A

Superheat is the temperature of the refrigerant vapor above its saturation temperature.

21
Q

Name at least three possible reasons why an evaporator coil may ice up.

A

Dirty air filter, Dirty evaporator coil, faulty belt or blower motor, faulty TXV, low refrigerant charge, low outdoor temperatures, etc…

22
Q

Name at least three possible reasons for a refrigeration circuit to be operating with a high head pressure.

A

Dirty condenser coil, faulty condenser fan motor, over charged, not enough condenser water flow, etc…

23
Q

What process is used to cool the water in a cooling tower?

A

Evaporation.

24
Q

Name two types electrical diagrams?

A

Pictorial diagram and ladder diagram(schematic)

25
Q

What is the normal position of a high pressure switch in an HVAC system?

A

Closed

26
Q

Is a chilled water loop open or closed?

A

Closed

27
Q

What is latent heat?

A

The heat required to change the physical state of a substance (solid to liquid, liquid to vapor). This heat does not raise the temperature.

28
Q

Briefly describe how evaporative cooling cools the air in a space.

A

Sensible heat is converted into latent heat as it evaporates the water. This effectively lowers the sensible heat in the air.

29
Q

Define Humidity.

A

It is basically moisture content in air or it is the quantity of water vapour retained by gas.

30
Q

What is Psychrometer?

A

Psychrometer is a device that uses the bulb thermometers to measure humidity. It is also used in air conditioning systems for maintaining humidity.

31
Q

What is Ambient Temperature?

A

The average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.

32
Q

Define Boiling Point

A

The temperature at which a substance in the liquid phase transforms to the gaseous phase.

33
Q

Which transducer converts heat energy into electrical energy

A

thermocouple

34
Q

What is the purpose of a Hot Gas Bypass valve?

A

Capacity control

Chief Study Guide (7 decks)

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