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Hvac > Air 51 B Final Test > Flashcards

Air 51 B Final Test Flashcards

Final test for commercial refrigeration

1
Q

Name the three most common types of air distribution systems.

A

A multiduct zone
b variable air volume
c double duct

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2
Q

. true or false. An EPA section 608 CAA license is required to work on lithium bromide

A

False

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3
Q

the power Pnumatic control system is delivered from _______

A

compressed air

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4
Q

On a 3 phase motor starter what in the primary protection of a load connect to the starter?

A

heater overloads

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5
Q

voltage unbalance in 3 phase circuit load cannot exceed___ %

A

2% rated value

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6
Q

to check a 3 phase motor winding t1- t2-t3 all resistance values

A

should be read the same on each winding

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7
Q

the purpose of a handoff switch on a motor control starters is to.

A

Permit automatic start stop from time clock or EMS system
and
Run the machinery in manual position for maintenance, repair, control circuit failure

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8
Q

What are the 5 components that make up a pneumatic control system.

A 
A. air supply
B.	relays
C.	switches
D.	controllers
E.	controlled devices
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9
Q

instead of using a compressor for energy an absorption chiller uses

A

hot water, steam and waste heat from cogeneration plant. (e: a,c &d above)

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10
Q

. true or false? An axial inline fan in series to airflow and parallel to blower shaft

A

true

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11
Q 
Axeil fans are divided into three main groups
A.	Propeller
B.	Tubexial
C.	Vanaxial
D.	All the above
A

D. All the above

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12
Q

what is the purpose of the inlet cone on an axial fan housing?

A

helps reduce the fan dynamic pressure and increased the static component or the total fan pressure

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13
Q

a Centrifugal fan is similar to a centrifugal pump excepts that it :

A

Pumps ‘Air”only

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14
Q

in order to reduce air pressure from the receiver tank to a working level, we must install a ______and ______ so we know where to set it.
.

A

in order to reduce air pressure from the receiver tank to a working level, we must install a GUAGE and REGULATOR so we know where to set it

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15
Q

A _____ ______ is used to properly sequence single, or multiple damper actuators.

A

A POSITIVE POSITIONER is used to properly sequence single, or multiple damper actuators.

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16
Q

to way valves are available in two types of body construction. what are those types?

A

A. Normally Open

B. Normally closed

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17
Q

What is the desired compressor run time?

A

1/3 to 1/2 the operating time

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18
Q

A three way mixing valve is piped with _____ inlets and a ____ outlet, referred as the common port

A

A three way mixing valve is piped with two inlets and a single outlet, referred as the common port

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19
Q

the output signal or branch line signal is a __ to __ PSIG pressure, which is _______ in relation to a change in sensed variable.

A

the output signal or branch line signal is a 3 to 15 PSIG pressure, which is LINEAR in relation to a change in sensed variable.

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20
Q

how is electric motor drive cooled on a hermetic centrifugal chiller?

A

Liquid refrigerant from chiller ( spray onto the windings)

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21
Q

the transmission of a centrifugal chiller consist of what two main components?

A. low speed shaft and gear
B. high speed shaft and gear
C. a and be above
D. none of the above

A

low speed shaft and gear
high speed shaft and gear

C. a and be above

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22
Q

What is the purpose of the emergency oil reservoir in lubrication cycle of the centrifugal chiller located at the top portion volute shell?

A

To lubricate when there’s a power failure

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23
Q

What is the purpose of the auxiliary oil pump on centrifugal chiller?

A

lubercates on startup on and shut down

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24
Q 
. the pre_rotation vane arm assembly on a centrifugal chiller is controlled by?
A.	pneumatic damper motor
B.	proportional (modulating) motor
C.	2-position spring return motor
D.	a and b above
A

pneumatic damper motor
proportional (modulating) motor
D. a and b above

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25
Q

the basic components of a centrifugal chiller compressor are the

A

impeller, diffuser and volute casing

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26
Q

Recovery of refrigerant in a centrifugal chiller is always ______ ________, followed by _______ _______.

A

Recovery of refrigerant in a centrifugal chiller is always LIQUID REFRIGERANT , followed by VAPOR REFRIGERANT.

27
Q

the first step in starting a chilled water system is to:

A

establish that there is chilled water flow

28
Q

water– cooled chillers must have water treatment to:

A

prevent minerals and algae from forming

29
Q

A ______ _____ system requires two different air pressure supplied to the thermostats, each for a different mode of operation.

A

A DUAL PRESSURE system requires two different air pressure supplied to the thermostats, each for a different mode of operation.

30
Q

The output or signal pressure maintained by the transmitter is ___ to ___ PSIG over the specific range of the transmitter.

A

The output or signal pressure maintained by the transmitter is 3 to 15 PSIG over the specific range of the transmitter.

31
Q

the main air supply is fed to the transmitter through:

A

a restrictor tee

32
Q

the humidity transmitter uses very sensitive ________ element to sense the relative humidity in the air.
t.

A

he humidity transmitter uses very sensitive HYGROSCOPIC element to sense the relative humidity in the air

33
Q

the throttling range represents a ________ of the transmitter span, which sensing the ______ _____.

A

the throttling range represents a PERCENTAGE of the transmitter span, which sensing the CONTROL MEDIUM

34
Q

When lithium bromide absorbs refrigerant it becomes diluted and cannot absorb water vapor. What items are needed to re-concentrate the solution

A

Generated pump and a heat source (C: A&B above)

35
Q

In an absorption chiller system the compressor that is used in a mechanical system is replaced by three parts Name them.

A

A. absorber
B. concentrator
C. pump

36
Q

the three types of lithium bromide solutions

A

the three types of lithium bromide solutions
A. concentrated
B. intermediate
C. diluted

37
Q

When lithium bromide is heated the salt and water separate by the process called

A

Distillation

38
Q

What is the absorbent or working solution in an absorption chiller.

A

Lithium Bromide

39
Q

In an absorption chiller what happens in the absorber section?
A. Refrigerant vapor is absorbed by the lithium bromide solution.
B. Refrigerant vapor releases the heat it acquired in the evaporator
C. absorption of refrigerant vapor creates a low pressure area within absorber
D. all of the above

A

D. all of the above

40
Q

How can you check the absorber vacuum levels?

A

U tube manometer and electronic vacuum gauges ( D: A&B above)

41
Q

Instead of using a compressor for energy an absorption chiller uses?

A

hot water
petroleum distillate
waste heat from cogeneration.

42
Q

what tools do you use when servicing absorption chillers?

A

Infrared thermometer and vacuum gauge.

43
Q

True or false. the purpose of the heat exchanger in the absorption refrigeration cycle is to save energy

A

TRUE

44
Q

Air leaking into absorption chiller causes what to happen
A. decrease in chiller capacity
B. increase heat output
C. increase concentration
D. increase evaporator pressure and template and pressure

A

E. all the above

45
Q

Which pump on the absorption chiller sprays lithium bromide solution.

A

absorber spray pump

46
Q

there are two types of stationary boilers

A

Fire tube and water tube

47
Q

the basic centrifugal chillers uses ______ to remove heat from the condenser
A. Sea water
B. open loop fresh water utilizing cooling towers
C. Ethylene glycol solution
D. a and b above

A

Sea water
open loop fresh water utilizing cooling towers
D. a and b above

48
Q

what setting or adjustment s can be made on a pneumatic receiver controller? List them

A

A. Action
B. set point
C. proportional band

49
Q

the _____ _____ _____ receiver controller utilizes the input from one transmitter and provides similar function to a _____ ______.

A

the SINGLE INPUT device receiver controller utilizes the input from one transmitter and provides similar function to a MASTER CONTROLLER.

50
Q

why do receiver controllers have a restricted main air supply piped to the sensor port?

A

Require constant air dutiablely

51
Q

What is the longest allowable distance from sensor to its restricted air supply?

A

200ft or 300 ft

52
Q

Landis & Gyr/Powers receiver controllers model RC195 have the following ports.(Ports)

A

Port1 Direct acting 100% authourity fixed
Port2 reverse acting 100% authority fixed
Port3 direct acting input connection
PortS supply air 22psig
PortC Control Air

53
Q

What is air stratification in a plenum? Explain in your own words.

A

The difference of the temp from one end of a room to another. (warmer on top, colder on bottom of space)

54
Q

A pneumatic room sensor can mounted up to how many feet from the receiver controller.

A

1000 ft.

55
Q

True or false . all transmitters are direct acting devices.

A

TRUE

56
Q

the centrifugal chillers utilizes two electric motor designs to run the chiller.

A

hermetic motor and open drive motor

57
Q

Cooling tower fans cycle on and off based on what type of control?
X

A

Cooling water return T-stat

58
Q

evaporatortive condensers uses more or less water that a cooling tower?

A

less (5%-10% less than that used in cooling towers)

59
Q

Controllers may either _____ ______ or _____ _____, and in some cases, may have the capability of being converted from one action to another

A

CONTROLLERS may either direct acting or reverse acting, and in some cases, may have the capability of being converted from one action to another

60
Q

Most pneumatic devices operate on a _____ PSIG main air supply.

A

Most pneumatic devices operate on a 20 PSIG main air supply.

61
Q

there two types of _____ _______ thermostats, the one-pipe or the ______ type thermostat and the two pipe or ______ type device.

A

there two types of SINGLE PRESSURE thermostats, the one-pipe or the BLEED type thermostat and the two pipe or RELAY type device.

62
Q

On multiple installation the suction line is

A.Larger than the main suction line

B.Smaller than the main suction line

C.Same size as the main suction line

D. Graduated in size with each size smaller than the preceding one.

A

B.Smaller than the main suction line

63
Q

What is a flooded evaporator coil?

A

A flooded evaporator has

  • liquid refrigerant in the entire coil
  • uses a float type metering device

DX Evaporator has

  • dry type
  • is has both liquid and superheated refrigerant present in coil.
  • multicircuited

Hvac (29 decks)

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