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4th Class - B2 > U-23: Heating Boiler & Heating System Controls > Flashcards

U-23: Heating Boiler & Heating System Controls Flashcards

0
Q

In a steam heating plant where does the steam give up most of its heat?

A

Radiators, convectors

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1
Q

What will cause grooving in the condensate receiver?

A

Carbon dioxide

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2
Q

Feed water supply to most steam boilers is usually controlled by?

A

Float switch

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3
Q

Hartford loop return line is connected where on a steam heating boiler?

A

It’s connected to the loop at the lowest safe water level

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4
Q

Second source heating boiler water is controlled by the low water fuel cut of device in two ways:

A

Electric feeder valve, float operated mechanical feeder valve

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5
Q

Bleeding water out of the control line on the condensate receiver will result in what?

A

Pressure drop in the control line

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6
Q

What happens at the highest operating level of the water in the boiler?

A

Feed water supply switch opens. Stopping the power supply to the control valve or supply pump. (Stops water supply to boiler)

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7
Q

When should a larger condensate receiver tank be used?

A

Systems extended over larger area

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8
Q

If control of the feed water supply is the primary function of the cut-off device what is required by code?

A

A second cut-off

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9
Q

The feed water control switch is commonly operated by?

A

low-water fuel cut-off float

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10
Q

What kind of pump requires a steaming heating boiler to be equipped with a Hartford loop?

A

Non positive displacement (centrifugal pump)

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11
Q

A feed water makeup supply should?

A

Be able to satisfy firing rate

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12
Q

An undersized condensate receiver may cause what?

A

Loss of condensate to the sewer

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13
Q

A condensate receiver low water cut-off will?

A

Stop the pump in order to prevent damage

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14
Q

What is a disadvantage of the float mechanism feeder?

A

Unsteady valve operation due to violent fluctuations of returning condensate

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15
Q

What’s the general rule for the size of a condensate receiver tank?

A

Be able to hold enough condensate equivalent to 20-30 minutes of normal water evaporation in the boiler

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16
Q

How can an operator get rid of carbon dioxide from ruining the condensate return lines?

A

Filming amines that will coat the metal

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17
Q

A float operated mechanical feeder valve should?

A

Not open until the level is well below the feed pump cut-in level

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18
Q

If multiple heating boilers require water which valve will open the pump switch to shut it off?

A

The valve that closes last

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19
Q

A thermal element, used on hot water boilers is capable of sending temperature and?

A

Converting it to a pressure signal

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20
Q

When the water level is insufficient or pump fails to start?

A

Fuel cut-off switch opens and cuts off the power to the fuel valve and sounds an alarm (double pole Mercury switch)

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21
Q

Neutralizing amines:

A

Raise the pH of condensate

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22
Q

A float operated mechanical feeder valve should:

A

Not open until the level is well below the feed pump cut-in level

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23
Q

Equalizing lines on a condensate receiver float chamber:

A

Will dampen water level fluctuations

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24
Q

What does ASME, Section IV cover?

A

Low water fuel cutoff.

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25
Q

List two types of Mercury pole switches:

A

Single/double pole

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26
Q

A high pressure fuel cut-off switch open when?

A

Gas pressure it too high

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27
Q

A damper positioning switch is used on boilers with a high-low fire control that has three positions:

A

Automatic, low, high

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28
Q

A low gas pressure cut off switch will shut down the burners due to?

A

Low gas pressure

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29
Q

When a boiler is shut down on the high limit control, what must the operator do before starting the boiler up again?

A

reset the lockout on the high limit controller

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30
Q

A low fire switch is part of the?

A

Start-up logic sequence

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31
Q

Automatic firing boilers that aren’t under constant supervision must be installed with a high limit control that shuts of the fuel supply to ensure pressure doesn’t raise above?

A

100 kPa

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32
Q

The bottom of the bellows is connected to a sensing bulb by means of a what?

A

Capillary tube

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33
Q

What kind of boilers are on-off controls most commonly used?

A

Low capacity boilers

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34
Q

The low air pressure fuel cut-off switch should be checked when air flow is?

A

Maximum

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35
Q

High limit control is used to shut down the fuel supply in the event of an elevated change in?

A

Steam pressure

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36
Q

The high gas pressure switch can be tested?

A

During the operation of the boiler

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37
Q

A thermal element, used on hot water boilers is capable of sending temperature and?

A

Converting it into a pressure signal

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38
Q

The temperature in the sensing bulb will be similar to the water where?

A

Leaving the boiler

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39
Q

What are the three distinct methods of burner operation control?

A

On-off, modulating, high-low

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40
Q

What does the aquastat control?

A

Burner circuit

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41
Q

To reduce cycling (starting and stopping of on-off device) what is installed?

A

A second spring (differential adjustment)

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42
Q

What is the pressure control device used for on steam boilers?

A

Starts and stops the burner to maintain the pressure within set limits

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43
Q

The operating pressure of a on-off device is controlled by what?

A

The tension of the large spring (increase in tension will raise operating pressure)

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44
Q

What must be adjusted in direct proportion to the firing rate of the burner to maintain the proper fuel-air ratio?

A

Air to the furnace

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45
Q

Three safety switches which are installed on all boiler equipped with an FD fan or blowers:

A

Low air pressure fuel cut-off
Low gas pressure fuel cut-off
High gas pressure fuel cut-off

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46
Q

List three methods of detecting flame failure on heating boilers:

A

Flame rod
Thermocouple
Photoelectric cell

47
Q

How are multiple thermocouples arranged so that they can provide enough electricity to control the fuel system?

A

In series, often called a thermopile

48
Q

A thermocouple used in conjunction with a gas valve must be inserted?

A

In the flame to work effectively

49
Q

What does ASME VI code describe?

A

Procedures for testing flame safeguard devices

50
Q

What is the photocell commonly called?

A

Scanner

51
Q

What reacts to infrared rays produced by a flame?

A

Lead-sulphide cells

52
Q

The infrared scanner should be mounted so that its temperature doesn’t exceed?

A

50 Celsius

53
Q

Ultraviolet scanners are mounted as close to flame without exceeding what temperature?

A

100 degrees Celsius

54
Q

Flame works on what principle when detecting a flame?

A

That a flame is capable of conducting electricity

55
Q

Fuel should be shut off immediately to prevent?

A

Furnace explosions

56
Q

What does a rectifying photocell consist of?

A

Cathode and anode

57
Q

What fuel is generally used with flame rods?

A

Gas burners

58
Q

What does a thermocouple consist of?

A

Two dissimilar metals (hot and cold junction)

59
Q

Rectifying photocell is also known as what?

A

Cad

60
Q

The outer sheath of a thermocouple used with a pilot burner is made of what metal?

A

Copper

61
Q

What is used in combination with a single thermocouple to provide enough electricity to shut the main fuel valve?

A

Transformer

62
Q

High limits temperature controls shut off fuel if the water temperature is?

A

Too high

63
Q

How long should it take for a flame rod to shut off the fuel due to flame failure?

A

4 seconds

64
Q

What does a photoelectric cell react to?

A

Infrared or ultraviolet rays

65
Q

List three types of photoelectric cell scanners:

A

Infrared scanner, ultraviolet scanner, rectifying photocell

66
Q

The piston is sealed to avoid air leakage in a piston type damper operator by using?

A

Rolling diaphragm

67
Q

What pressure does the reducing valve maintain supplied air at?

A

103 kPa

68
Q

What are the two classes controllers are divided into?

A

Bleeding, non bleeding type

69
Q

The sensing element of humidistats reacts to a change in?

A

Humidity

70
Q

What are the two basic types of dampers?

A

Opposed and Parallel blade

71
Q

The device used to maintain a constant pressure throughout a pneumatic control system is called?

A

A reducing valve

72
Q

When the controller increase the control pressure on an increase in controlled condition it’s called?

A

Direct acting

73
Q

A pneumatic control systems uses a sensing device to change?

A

Pressure in the control line

74
Q

What are the three pneumatic controlled devices?

A

Dampers, pilot positioned, damper operators

75
Q

The effective range of control pressure used in a 103 kPa circuit is usually considered to be between?

A

20-90 kPa

76
Q

What does a non bleed pneumatic controller bleed air?

A

When output pressure is reduced

77
Q

In a self contained control system the energy for operation is provided by the reaction of the?

A

Sensing device

78
Q

A pneumatic relay is activated by the control signal from one or more?

A

Controllers

79
Q

What do pneumatic control systems operate by means of?

A

Compressed air signal

80
Q

What do the sensing elements on a pneumatic controller measure?

A

Change in temperature, humidity or pressure in controlled space

81
Q

Pneumatic control systems consist of four essential parts:

A

Air compressor, air pipping/tubing, controllers, controlled devices

82
Q

Pneumatic electric switches often control the operation of four pieces of equipment:

A

Valves
Pumps
Compressors
Fans

83
Q

A bimetal thermostat operating temperature range is between?

A

10-32 degrees Celsius

84
Q

Remote bulb thermostat thermostats sensing bulb/capillary tube/bellows combination contains what liquid?

A

Volatile

85
Q

A term that refers to the normal electric supply voltage

A

Line voltage

86
Q

The sensing device of a humidistat consists of?

A

A hygroscopic element

87
Q

A device used to change AC voltage from one value to another

A

Transformer

88
Q

An electric radiator valve is an?

A

On/off valve

89
Q

On-off switches are equipped with an open?

A

Contact switch

90
Q

A device used to control the flow of fluid, gas, water, air or steam

A

Control valve

91
Q

A device used to position dampers and control valves

A

Actuator

92
Q

Three way valves are used in hydronic heating systems for?

A

Either mixing or diverting service

93
Q

A device used to control the flow of air in a duct or through a wall louvre

A

Damper

94
Q

A device that connects an actuator to a damper or control valve

A

Linkage

95
Q

A device which reacts to pressure, humidity, temperature to provide a two position floating or pro portioning control of an actuator or relay

A

Controller

96
Q

Thermostats should be mounted how many meters above floor on an inside wall?

A

1.5m

97
Q

A term that refers to wiring or other electrical devices using 30 volts or less

A

Extra low voltage

98
Q

Simplest form of a controller output?

A

Two position

99
Q

An example of an output device is an?

A

Actuator

100
Q

A final control element is positioned by a controller output signal which first goes to?

A

An output device

101
Q

The input circuits for many electronic controller can accept a voltage range of?

A

1-10 volts DC

102
Q

A device such as an valve or damper that changes the value of the controlled variable

A

Final control element

103
Q

An electronic pressure sensor is usually a transmitter that converts pressure into a variable such as…

A

Voltage, current or resistance

104
Q

An electric controller is used to position an?

A

Actuator

105
Q

The actual value of a controlled variable

A

Control point

106
Q

What consists of a sensor controller and a final control element

A

Electric control system

107
Q

A device or component that measures the variable to be controlled

A

Main sensor

108
Q

Resistance temperature devices can provide a relatively linear resistance from?

A

-40-120 degrees Celsius

109
Q

There are two types of sensors most commonly used

A

Analog and digital

110
Q

What changes the value of a controlled variable?

A

Proportional controller

111
Q

In an electronic control system what are analog sensors used for?

A

Continuously changing conditions

112
Q

Temperature sensors are classified into three groups:

A

RTDs, thermistors, thermocouples

113
Q

A device that converts one energy form to another

A

Transducer

114
Q

A device that receives a signal from one source then sends a corresponding signal to a receiver

A

Transformer

4th Class - B2 (32 decks)

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