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

U-23: Heating Boiler & Heating System Controls Flashcards

(115 cards)

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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
What does ASME, Section IV cover?
Low water fuel cutoff.
25
List two types of Mercury pole switches:
Single/double pole
26
A high pressure fuel cut-off switch open when?
Gas pressure it too high
27
A damper positioning switch is used on boilers with a high-low fire control that has three positions:
Automatic, low, high
28
A low gas pressure cut off switch will shut down the burners due to?
Low gas pressure
29
When a boiler is shut down on the high limit control, what must the operator do before starting the boiler up again?
reset the lockout on the high limit controller
30
A low fire switch is part of the?
Start-up logic sequence
31
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?
100 kPa
32
The bottom of the bellows is connected to a sensing bulb by means of a what?
Capillary tube
33
What kind of boilers are on-off controls most commonly used?
Low capacity boilers
34
The low air pressure fuel cut-off switch should be checked when air flow is?
Maximum
35
High limit control is used to shut down the fuel supply in the event of an elevated change in?
Steam pressure
36
The high gas pressure switch can be tested?
During the operation of the boiler
37
A thermal element, used on hot water boilers is capable of sending temperature and?
Converting it into a pressure signal
38
The temperature in the sensing bulb will be similar to the water where?
Leaving the boiler
39
What are the three distinct methods of burner operation control?
On-off, modulating, high-low
40
What does the aquastat control?
Burner circuit
41
To reduce cycling (starting and stopping of on-off device) what is installed?
A second spring (differential adjustment)
42
What is the pressure control device used for on steam boilers?
Starts and stops the burner to maintain the pressure within set limits
43
The operating pressure of a on-off device is controlled by what?
The tension of the large spring (increase in tension will raise operating pressure)
44
What must be adjusted in direct proportion to the firing rate of the burner to maintain the proper fuel-air ratio?
Air to the furnace
45
Three safety switches which are installed on all boiler equipped with an FD fan or blowers:
Low air pressure fuel cut-off Low gas pressure fuel cut-off High gas pressure fuel cut-off
46
List three methods of detecting flame failure on heating boilers:
Flame rod Thermocouple Photoelectric cell
47
How are multiple thermocouples arranged so that they can provide enough electricity to control the fuel system?
In series, often called a thermopile
48
A thermocouple used in conjunction with a gas valve must be inserted?
In the flame to work effectively
49
What does ASME VI code describe?
Procedures for testing flame safeguard devices
50
What is the photocell commonly called?
Scanner
51
What reacts to infrared rays produced by a flame?
Lead-sulphide cells
52
The infrared scanner should be mounted so that its temperature doesn't exceed?
50 Celsius
53
Ultraviolet scanners are mounted as close to flame without exceeding what temperature?
100 degrees Celsius
54
Flame works on what principle when detecting a flame?
That a flame is capable of conducting electricity
55
Fuel should be shut off immediately to prevent?
Furnace explosions
56
What does a rectifying photocell consist of?
Cathode and anode
57
What fuel is generally used with flame rods?
Gas burners
58
What does a thermocouple consist of?
Two dissimilar metals (hot and cold junction)
59
Rectifying photocell is also known as what?
Cad
60
The outer sheath of a thermocouple used with a pilot burner is made of what metal?
Copper
61
What is used in combination with a single thermocouple to provide enough electricity to shut the main fuel valve?
Transformer
62
High limits temperature controls shut off fuel if the water temperature is?
Too high
63
How long should it take for a flame rod to shut off the fuel due to flame failure?
4 seconds
64
What does a photoelectric cell react to?
Infrared or ultraviolet rays
65
List three types of photoelectric cell scanners:
Infrared scanner, ultraviolet scanner, rectifying photocell
66
The piston is sealed to avoid air leakage in a piston type damper operator by using?
Rolling diaphragm
67
What pressure does the reducing valve maintain supplied air at?
103 kPa
68
What are the two classes controllers are divided into?
Bleeding, non bleeding type
69
The sensing element of humidistats reacts to a change in?
Humidity
70
What are the two basic types of dampers?
Opposed and Parallel blade
71
The device used to maintain a constant pressure throughout a pneumatic control system is called?
A reducing valve
72
When the controller increase the control pressure on an increase in controlled condition it's called?
Direct acting
73
A pneumatic control systems uses a sensing device to change?
Pressure in the control line
74
What are the three pneumatic controlled devices?
Dampers, pilot positioned, damper operators
75
The effective range of control pressure used in a 103 kPa circuit is usually considered to be between?
20-90 kPa
76
What does a non bleed pneumatic controller bleed air?
When output pressure is reduced
77
In a self contained control system the energy for operation is provided by the reaction of the?
Sensing device
78
A pneumatic relay is activated by the control signal from one or more?
Controllers
79
What do pneumatic control systems operate by means of?
Compressed air signal
80
What do the sensing elements on a pneumatic controller measure?
Change in temperature, humidity or pressure in controlled space
81
Pneumatic control systems consist of four essential parts:
Air compressor, air pipping/tubing, controllers, controlled devices
82
Pneumatic electric switches often control the operation of four pieces of equipment:
Valves Pumps Compressors Fans
83
A bimetal thermostat operating temperature range is between?
10-32 degrees Celsius
84
Remote bulb thermostat thermostats sensing bulb/capillary tube/bellows combination contains what liquid?
Volatile
85
A term that refers to the normal electric supply voltage
Line voltage
86
The sensing device of a humidistat consists of?
A hygroscopic element
87
A device used to change AC voltage from one value to another
Transformer
88
An electric radiator valve is an?
On/off valve
89
On-off switches are equipped with an open?
Contact switch
90
A device used to control the flow of fluid, gas, water, air or steam
Control valve
91
A device used to position dampers and control valves
Actuator
92
Three way valves are used in hydronic heating systems for?
Either mixing or diverting service
93
A device used to control the flow of air in a duct or through a wall louvre
Damper
94
A device that connects an actuator to a damper or control valve
Linkage
95
A device which reacts to pressure, humidity, temperature to provide a two position floating or pro portioning control of an actuator or relay
Controller
96
Thermostats should be mounted how many meters above floor on an inside wall?
1.5m
97
A term that refers to wiring or other electrical devices using 30 volts or less
Extra low voltage
98
Simplest form of a controller output?
Two position
99
An example of an output device is an?
Actuator
100
A final control element is positioned by a controller output signal which first goes to?
An output device
101
The input circuits for many electronic controller can accept a voltage range of?
1-10 volts DC
102
A device such as an valve or damper that changes the value of the controlled variable
Final control element
103
An electronic pressure sensor is usually a transmitter that converts pressure into a variable such as...
Voltage, current or resistance
104
An electric controller is used to position an?
Actuator
105
The actual value of a controlled variable
Control point
106
What consists of a sensor controller and a final control element
Electric control system
107
A device or component that measures the variable to be controlled
Main sensor
108
Resistance temperature devices can provide a relatively linear resistance from?
-40-120 degrees Celsius
109
There are two types of sensors most commonly used
Analog and digital
110
What changes the value of a controlled variable?
Proportional controller
111
In an electronic control system what are analog sensors used for?
Continuously changing conditions
112
Temperature sensors are classified into three groups:
RTDs, thermistors, thermocouples
113
A device that converts one energy form to another
Transducer
114
A device that receives a signal from one source then sends a corresponding signal to a receiver
Transformer

4th Class - B2 (32 decks)

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