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2nd year sheet metal > Furnace commissioning > Flashcards

Furnace commissioning Flashcards

(117 cards)

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1
Q

What type of pump would be used to lift water in below grade submersed situations?

A

Sump pump

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2
Q

What is the purpose of a foot valve?

A

Prevent water from leaving the suction line

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3
Q

How is a sump or sewage pump controlled?

A

Float switch

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4
Q

What are materials that readily give up their electrons called?

A

Conductors

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5
Q

What must happen when measuring resistance of a device in a circuit?

A

Disconnect the device being checked and place the test leads in series with the device

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6
Q

Which type of pilot burner draws primary air into the burner at the point of combustion eliminating the chance of dust to be present?

A

Post aerated pilot

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7
Q

What can happen if a pilot burner is not adjusted properly and metal is impinging in the pilot flame?

A

The flame will cool and cause incomplete combustion

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8
Q

Describe a heating thermostat.

A

Temperature sensing switch that closes on temperature fall

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9
Q

What happens in the furnace when the high limit switch opens?

A

Gas flow is turned off and the blower is energized

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10
Q

What is the purpose of a draft hood in a gas appliance?

A

Provide a break in the stack action and prevent the products of combustion from down drafting and entering the heat exchanger

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11
Q

What device can control one or more initiating devices in a circuit?

A

Relay

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12
Q

What type of capacitor would be used with a single phase motor?

A

Run capacitor

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13
Q

What unit of measure is used for testing capacitors?

A

Farads

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14
Q

When referencing flow of the products of combustion, where in a gas furnace is the inducer motor located?

A

Downstream of the burner and heat exchanger

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15
Q

Which safety limit switch automatically resets?

A

Main high limit

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16
Q

What is the recommended spark gap for the pilot ignition spark?

A

1/8”

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17
Q

What is the purpose of a dirt pocket when installed at the appliance gas line drop?

A

Collect filings and foreign materials

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18
Q

What gas line material is used above ground, can be cut to any length, uses manufactured specialty fittings and is flexible for fewer connections?

A

CSST-corrugated stainless steel tubing

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19
Q

How far must the vent of a regulator be from a moisture exhaust vent?

A

3’

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20
Q

What needs to be done to a gas appliance when installing at high altitudes as per specifications?

A

Derate by 10% for altitudes between 2000’ and 4500’. Over 4500’, the input rating shall be reduced at the rate of 4% for each additional 1000’. (Decrease BTUH)

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21
Q

What is required for the safe operation of a water boiler if the system drains?

A

Low level cut off

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22
Q

What are 2 main principles in flame rod detection?

A

Flame rectification and flame conductivity

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23
Q

What type of ignition system, on a call for heat, lights the pilot, proves the pilot is lit, lights the main burner, proves the main burner and then shuts off the pilot as it is no longer needed?

A

Interrupted pilot ignition

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24
Q

What type of system uses a spark to light the main burner?

A

Direct spark ignition

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25
What is required for the flame proving circuit to become rectified?
The larger ratio between the ground and flame rod allowing current to flow more in one direction
26
What function does a CPU perform in a gas furnace?
Executes a series of stored instructions
27
What can be used to adjust fan off timers in a gas furnace?
Dip switch
28
What are the more reliable hot surface igniters made of- silicone carbide or silicone nitride?
Silicone nitride
29
Name 3 approved gas leak detection methods?
Soapy water solution, test dial, electronic leak detector
30
What type of venting must be used when installing a condensing gas appliance?
BH vent
31
If the temperature rise in a furnace is too high, what must be done according to the rating plate?
Increase fan speed
32
What type of pilot burner uses primary air and secondary air for combustion and burn continuously?
Aerated standing pilot burner
33
What needs to be done to the pilot burner when converting fuels from natural gas to propane?
Change the insert orifice to a smaller sized orifice
34
What does a heat anticipator accomplish in a mechanical thermostat?
Lessen room temperature swings
35
Which high limit safety device comes with a manual reset button?
Flame roll out
36
What 3 components make up the atom?
Electrons, neutrons and protons
37
What are the electrons in the outermost orbit of an atom called?
Valence
38
Materials that easily give up electrons are known as?
Conductors
39
Current can be described as the flow of ____________ which is measured in ____________?
Electrons, amperes
40
What is the unit of measure for the number of cycles per second, when referencing alternating current?
Hertz
41
Name 3 examples of electromotive force that can produce voltage?
Magnetic, heat and friction
42
What 3 things are required for electricity to flow?
Path, source and load
43
In this electrical circuit, what component would be considered the load- battery light bulb switch or transformer?
Light bulb
44
What is a continuity test used to determine?
If an electrical circuit is complete
45
What can be used to check an electrical circuit for live voltage?
Voltage pen or test light
46
What type of meter should never be connected to an energized circuit?
Ohmmeter
47
When comparing schedule 40 and schedule 80 pipe, what happens to the inside diameter as the wall thickness increases?
Inside diameter decreases
48
When threading pipe, what is the cutting fluid used for?
To help keep the pipe and threading dies cool
49
When the pipe has been cut to the correct length, what must be done before threading begins?
Clean die threads, ream pipe and oil
50
What type of piping cannot be used in above ground installations?
Polyethylene
51
What is the definition of thread engagement?
The amount of pipe that is added to a face to face measurement
52
Why is teflon tape or pipe dope used on an iron thread?
Lubricate the joint
53
What is type M copper used for?
Potable water
54
In HVAC, where can aluminum tubing be used?
Pilot gas from gas valve to pilot burner
55
What must be done if a gas furnace heat exchanger is deemed defective?
Replace with same approved heat exchanger
56
What must be installed in conjunction with a regulator?
Shut off valve
57
What would a plugged regulator vent cause?
An increase in outlet pressure
58
What is it called when the flow of gas has stopped completely by the regulator?
Lock up
59
What is the minimum distance between a regulator vent termination and mechanical air intake?
10'
60
What is the area of the common manifold when venting 2 or more regulators together, without internal relief?
2 x the total area of the connected bleed vents
61
What is the maximum pressure setting of the 1st stage regulator in a residential propane installation?
No more than 10 psig
62
What are the 3 main elements of a regulator?
Orifice (the restricting element), diaphragm (the measuring element) and spring (the loading element)
63
What is an orifice designed to do?
Control rate of flow of gas to the burner
64
What is the proper way to verify the actual size of an orifice?
Using the shank of the orifice drill
65
What is a leak limiting device used for?
To limit the amount of gas escaping if the diaphragm ruptures. (1cu.ft/hr for propane and 2.5cu.ft/hr for natural gas
66
When is a leak limiting device used?
On 2psig or lower pressure systems in a well ventilated space only
67
What 2 devices on a regulator, are used to control excess pressure?
Internal and external relief valves
68
How is a regulator freeze up identified?
By a lack of gas to the burners (slow or sluggish operation)
69
What does a plugged regulator vent cause?
Excessively high outlet pressures
70
What position does a gas valve fail in?
Closed position
71
Name 4 types of pressure regulators?
Service, system, appliance and servo
72
What closes the regulator valve stem?
Gas pressure
73
How do you change rotation in a belt drive motor?
Reverse the wires under the cover plate
74
How do you test a low water cut off control on a boiler?
Drain the boiler
75
What type of valve is used on a propane tank for liquid withdrawal?
Excess flow valve
76
How close to the side of a building can an RTU be located?
6'
77
How far from a masonry wall does a 7500L propane tank have to be located?
10’ or 3m
78
What needs to be checked on a transformer if it has been replaced multiple times?
VA rating
79
How many support legs minimum are needed on a horizontal propane tank?
2
80
What type of pipe is not allowed for liquid propane and cannot be used in above ground installations?
Polyethylene
81
What are the LEL and UEL for propane?
2.3% to 9.5%
82
What are the LEL and UEL for natural gas?
5% to 15%
83
What is the piping between the well head and the processor called?
Production lines
84
What is the piping between the city gate and the building called?
Distribution lines
85
What type of venting is used on a high efficient oil fired furnace?
L vent
86
How must a steam boiler be wired for an operator control and a safety control- series and series parallel and series parallel
Series and series
87
What class category is a 24 volt transformer?
Class 2
88
What common voltage, used in furnaces, is found on the secondary side of a transformer?
24V
89
When testing resistance, how must the meter be hooked up and is the circuit energized or deenergized?
The circuit is deenergized and the meter leads are hooked up in series
90
On a gas fired residential furnace, where would the main high limit switch be located?
Next to the heat exchanger
91
What is determined by clocking the gas meter?
BTUH input of the appliance
92
Calculate the BTUH for a natural gas fired furnace that took 45 seconds to complete 1 revolution on a 1 cubic foot dial?
1/45=0.0222 x 3600=80 This gives you the cubic feet of gas, now you need to multiply that by the calorific value of the fuel to get the BTUH. 80 x 1000= 80,000 BTUH
93
What must be done to the fan speed if the temperature rise in a furnace is too high according to the rating plate?
Fan speed should be increased
94
How do you test the high limit in a gas fired residential furnace?
Disconnect the heating fan speed wire from the terminal and do a call for heat.
95
What happens to the pilot in an intermittent and interrupted ignition system?
Intermittent-pilot stays on after main burner is lit Interrupted-pilot turns off after main burner is lit
96
What is the included angle of a NPT (National Pipe Thread)?
60 degrees
97
What is cutting oil used for in threading pipe?
Keeps the pipe and threading dies cool
98
Term used when a fitting has been over tightened onto a pipe?
Creeping
99
What is the amperage of a 120 volt circuit that has a 10 ohm light and a 50 ohm fan motor wired in series?
Add up the ohms and divide this into the volts to get the amps. 10 + 50 = 60 ohms 120/60 = 2 amps
100
What is the voltage of a series circuit with 4-15 ohm lights and a 5 amp draw?
Add up ohms and multiply by the amperage. 15 + 15 + 15 + 15 = 60 ohms 60 x 5 = 300 volts
101
What is the purpose of a draft hood in a gas appliance?
Prevents down drafts from enter the heat exchanger
102
From the list, which safety switch automatically resets? Roll out Spill Blocked vent Main high limit
Main high limit-once cabinet cools down, the limit switch will reset.
103
What is the area of the common manifold when venting 2 or more regulators together, with internal relief?
The manifold (single vent line) has an area equal to the largest relief valve opening plus 50% of the total area of the other relief valve openings.
104
What can cause damage to the copper fins of a heat exchanger on a boiler?
Low or no water
105
How do you set the heat anticipator on a thermostat?
The amp draw stated on the gas valve
106
What is formed when you chemically combine 2 elements?
A compound
107
What 2 things can turn on the blower motor on a standard or low efficient furnace?
Fan control Summer switch
108
What does the operating control on a boiler respond to?
Temperature
109
If a diaphragm relief valve is blocked, what position will the diaphragm be in?
Closed position
110
How do you reverse the direction of a belt driven fan?
Reverse the hot leads (wires)
111
How is combustion air usually installed?
Insulated pipe or flex
112
Which schedule of pipe has a larger interior diameter-schedule 40 or schedule 80?
Schedule 40 Schedule 80 has thicker walls and a smaller interior diameter.
113
What causes cavitation in a centrifugal pump?
Gas bubbles, a vacuum, a choked off suction line
114
When taking a supply air temperature reading, where would you insert the probe?
Away from the line of sight of the heat exchanger
115
How long does an HSI glow for?
17-34 seconds
116
Who approves the conversion of an appliance from propane to natural gas?
The authority having jurisdiction
117
What automated sequence occurs in a furnace prior to ignition?
Pre purge

2nd year sheet metal (5 decks)

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