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Course L > Gas - Unit O > Flashcards

Gas - Unit O Flashcards

1
Q

What will happen if you connect a DC meter with the wrong polarity?

A

Possible damage - Meter tries to deflect the wrong way.

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2
Q

Voltmeters must be connected in ______ with the device across which the voltage is being measured.

A

Parallel.

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3
Q

In-line ammeters must be connected in ____ with the device through which the currect is being measured.

A

Series.

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4
Q

What do ohmmeters measure?

A

Resistance.

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5
Q

Can a clamp-on ammeter measure current without interrupting the circuit?

A

Yes.

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6
Q

Can an ohmmeter be used on a live circuit?

A

No - The meter can be damaged.

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7
Q

Name the main components of a neon light test.

A

Neon lamp, insulated test leads.

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8
Q

What is the minimum voltage required to make a neon test light glow?

A

50 Volts.

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9
Q

What are the two main types of multimeters?

A

Analogue.

Digital[][][]]

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10
Q

Which type of multimeter is more difficult to read: Analogue or Digital?

A

Analogue.

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11
Q

Name the force that is needed to move current through a circuit?

A

Voltage.

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12
Q

What limits current flow through a circuit?

A

Resistance.

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13
Q

Name four situations that cause unwanted resistance.

A

Corroded terminals.

Defective components.

Improper wire splices[]]

Loose connections[][][][]

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14
Q

Name three voltage ranges used in the gas fitting trade.

A

24 volts - For control circuits.

120 volts - Line voltage - For fans, motors, pumps.

Millivoltage - Control and safety circuits[][][][][][][][][]]

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15
Q

Desrcribe the procedure used to determine if the appliance disconnect is wired into the hot supply to the apliance.

A

Open the switch and see if either lead is still hot to ground.

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16
Q

Why is it important to check the test meter for polarity when connecting the test leads to a circuit powered by DC current?

A

Flash test to prevent damage when needle goes wrong way.

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17
Q

Very brief contact to check direction of needle travel is the definition of?

A

Flash test.

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18
Q

When testing thermocouples with a millivoltmeter, indicate the normal values for the following tests:

Open ciruit.

Closed circuit.

Miniumum closed circuit voltage before replacement.

Drop out range of pilotstat coil[][][][][][][][][][][][][][][][][][][][][]

A

Open circuit: 30 mV.

Closed circuit: 15 mV.

Min closed circuit voltage before replacement: 10 mV.

Drop out range of pilotstat coil: 5 - 2 mV[][][][][][][][][][][][]]

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19
Q

Name the type of transformer that is used to reduce 120 VAC to 24 VAC.

A

Stepdown transformer.

20
Q

Name the type of transformer that is used to increase 120 VAC to 6,000 VAC.

A

Stepup transformer.

21
Q

A transformer consists of two coils. They are known as the ______ coil and the ________ coil.

A

Primary and Secondary.

22
Q

What factors will determine the secondary voltage of the transformer?

A

The primary voltage and the turns ratio.

23
Q

Explain how power is induced into the secondary coil of the transformer.

A

The expanding and contracting of the magnetic field of the primary coil is induced into the secondary coil.

24
Q

Describe the result of excessive voltage to primary windings.

A

Causes excessive secondary voltage and transformer overheating.

25
Q

Describe the result of insufficient voltage to primary windings.

A

No harm results, but secondary voltage is low.

26
Q

Describe the results of exceeding the power consumption of the secondary side of the transformer.

A

Causes secondary voltage to decrease, but worse, the power rating is exceeded, causing overheating and possible damage.

27
Q

List two units of power used to rate transformer secondary windings.

A

Watts.

Voltampere.

28
Q

List two rules to use to avoid overloading or exceeding the rating of a transformer.

A

Never apply more than the rated voltage to primary.

Never draw more than the rated current from secondary.

29
Q

Which of the following meters has a very high internal resistance?

A. Voltmeter.

B. Ammeter[]]

C. Ohmmeter.

D. Velometer[]

A

A. Voltmeter.

30
Q

Which of the following meters has it’s own source of EMF?

A. Voltmeter.

B. Ammeter[]

C. Ohmmeter.

D. Velometer[]

A

C. Ohmmeter.

31
Q

If the leads of an ohmmeter are connected together and the scale is adjusted correctly, the meter should read:

A. Infinite resistance.

B. Ultimate resistance.

C. The resistance of the meter.

D. Zero Resistance[][][][][][][][][][][]]

A

D. Zero Resistance.

32
Q

If the leads of an ohmmeter are connected across the terminals of a broken coil, the meter should read:

A. Infinite resistance.

B. Ultimate resistance.

C. The resistance of the meter.

D. Zero resistance[][][][][][][][][][][][]

A

A. Infinite resistance.

33
Q

If the leads of an ohmmeter are connected across a closed switch, the meter should read:

A. Infinite resistance.

B. Ultimate resistance.

C. The resistance of the meter.

D. Zero resistance[][][][][][][][][][][][]

A

D. Zero resistance.

34
Q

If the leads of an ohmmeter are connected across the contacts of a relay coil, the meter should read:

A. Infinite resistance.

B. Ultimate resistance.

C. The resistance of the coil.

D. Zero resistance[][][][][][][][][][]

A

C. The resistance of the coil.

35
Q

A pilotstat coil should produce sufficient magnetic field to hold the safety open with a minimum applied voltage of:

A. 30 millivolts.

B. 15 millivolts[]

C. 8 millivolts[][]

D. 6 millivolts[][]]

A

D. 6 millivolts.

36
Q

If a pilotstat coil fails to produce sufficient magnetic field to hold the safety open with 2-5 millivolts applied voltage, we consider the coil to be:

A. Extremely weak and should be replaced.

B. Too weak to perform it’s function and must be replaced.

C. Providing normal operation[][][][][][][][][][][][][][][][][][][][][][][][][][][]]

D. Underpowered and the thermocouple needs replacing[][

A

C. Providing normal operation.

37
Q

During the servicing of a furnace equipped with a thermocouple safety you blow out the pilot flame. If the safety valve meets Code requirements and uses natural gas, it should fail closed within:

A. 4 seconds.

B. 10 seconds.

C. 60 seconds.

D. 90 seconds[]

A

D. 90 seconds.

[Propane is 20 seconds]

38
Q

To test a thermocouple and pilotstat coil, the test adaptor must be wired in:

A. Series with the coil.

B. Parallel with the coil.

C. Parallel with the coil and thermocouple.

D. Series w the coil but in parallel with the thermocouple.

A

A. Series with the coil.

39
Q

When using a thermocouple to power a control circuit with a thermostat, the thermostat should be located no more than ______ from the gas valve.

A. 15 feet.

B. 30 feet.

C. 50 feet.

D. 100 feet.

A

B. 30 feet.

40
Q

When a 500 mV thermopile is tested under load, it should produce approximately:

A. 500 mV.

B. 400 mV.

C. 250 mV.

D. 30 mV[][]

A

C. 250 mV.

41
Q

When testing a millivoltage control system, the voltage drop across the thermostat (with anticipator) and wires should be approximately:

A. 10 mV.

B. 110 mV.

C. 250 mV.

D. 500 mV[]

A

B. 110 mV.

42
Q

When testing a millivoltage control system, a voltage drop across the gas valve coil in excess of 150 mV indicates:

A. The thermopile is weak.

B. The gas valve coil is weak.

C. The high limit is open[][][][][][]

D. The system is in good condition.

A

D. The system is in good condition.

43
Q

When testing a millivoltage control system, the thermopile produces 300 mV but a voltage check across the gas valve coil indicates only 125 mV. This may indicate the:

A. Thermopile is weak.

B. Gas valve coil is weak.

C. High limit is open[][][][][][]

D. System has excessive resistance.

A

D. System has excessive resistance.

44
Q

When responding to a no heat call, the first check to make is:

A. Check the thermostat heat anticipator.

B. Check for gas pressure at the appliance.

C. Check for power at the appliance[][][][][][][]

D. Check ignition module for spark[][][][][][][][]]

A

C. Check for power at the appliance.

45
Q

When checking the flame signal current for an S86 ignitioin module, the reading should be at least:

A. 1 amp.

B. 1.5 amps.

C. 1.5 microamps.

D. 5 microamps[][]

A

C. 1.5 microamps.

46
Q

An S860 direct spark ignition module with hot surface ignition provides 3 trials for ignition. If the main flame is lost during the run cycle of the burner, the control will next:

A. Shut off main gas valve and heat up hot surface ignitor.

B. shut off pilot and main gas and begin prepurge timing[]]

C. Shut off main gas and begin prepurge timing[][][][]][][][][][]]

D. Go to lockout[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]

A

C. Shut off main gas and begin prepurge timing.

Course L (30 decks)

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