Gas - Unit O Flashcards
What will happen if you connect a DC meter with the wrong polarity?
Possible damage - Meter tries to deflect the wrong way.
Voltmeters must be connected in ______ with the device across which the voltage is being measured.
Parallel.
In-line ammeters must be connected in ____ with the device through which the currect is being measured.
Series.
What do ohmmeters measure?
Resistance.
Can a clamp-on ammeter measure current without interrupting the circuit?
Yes.
Can an ohmmeter be used on a live circuit?
No - The meter can be damaged.
Name the main components of a neon light test.
Neon lamp, insulated test leads.
What is the minimum voltage required to make a neon test light glow?
50 Volts.
What are the two main types of multimeters?
Analogue.
Digital[][][]]
Which type of multimeter is more difficult to read: Analogue or Digital?
Analogue.
Name the force that is needed to move current through a circuit?
Voltage.
What limits current flow through a circuit?
Resistance.
Name four situations that cause unwanted resistance.
Corroded terminals.
Defective components.
Improper wire splices[]]
Loose connections[][][][]
Name three voltage ranges used in the gas fitting trade.
24 volts - For control circuits.
120 volts - Line voltage - For fans, motors, pumps.
Millivoltage - Control and safety circuits[][][][][][][][][]]
Desrcribe the procedure used to determine if the appliance disconnect is wired into the hot supply to the apliance.
Open the switch and see if either lead is still hot to ground.
Why is it important to check the test meter for polarity when connecting the test leads to a circuit powered by DC current?
Flash test to prevent damage when needle goes wrong way.
Very brief contact to check direction of needle travel is the definition of?
Flash test.
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[][][][][][][][][][][][][][][][][][][][][]
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[][][][][][][][][][][][]]
Name the type of transformer that is used to reduce 120 VAC to 24 VAC.
Stepdown transformer.
Name the type of transformer that is used to increase 120 VAC to 6,000 VAC.
Stepup transformer.
A transformer consists of two coils. They are known as the ______ coil and the ________ coil.
Primary and Secondary.
What factors will determine the secondary voltage of the transformer?
The primary voltage and the turns ratio.
Explain how power is induced into the secondary coil of the transformer.
The expanding and contracting of the magnetic field of the primary coil is induced into the secondary coil.
Describe the result of excessive voltage to primary windings.
Causes excessive secondary voltage and transformer overheating.
Describe the result of insufficient voltage to primary windings.
No harm results, but secondary voltage is low.
Describe the results of exceeding the power consumption of the secondary side of the transformer.
Causes secondary voltage to decrease, but worse, the power rating is exceeded, causing overheating and possible damage.
List two units of power used to rate transformer secondary windings.
Watts.
Voltampere.
List two rules to use to avoid overloading or exceeding the rating of a transformer.
Never apply more than the rated voltage to primary.
Never draw more than the rated current from secondary.
Which of the following meters has a very high internal resistance?
A. Voltmeter.
B. Ammeter[]]
C. Ohmmeter.
D. Velometer[]
A. Voltmeter.
Which of the following meters has it’s own source of EMF?
A. Voltmeter.
B. Ammeter[]
C. Ohmmeter.
D. Velometer[]
C. Ohmmeter.
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[][][][][][][][][][][]]
D. Zero Resistance.
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. Infinite resistance.
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[][][][][][][][][][][][]
D. Zero resistance.
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[][][][][][][][][][]
C. The resistance of the coil.
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[][]]
D. 6 millivolts.
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[][
C. Providing normal operation.
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[]
D. 90 seconds.
[Propane is 20 seconds]
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. Series with the coil.
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.
B. 30 feet.
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[][]
C. 250 mV.
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[]
B. 110 mV.
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.
D. The system is in good condition.
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.
D. System has excessive resistance.
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[][][][][][][][]]
C. Check for power at the appliance.
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[][]
C. 1.5 microamps.
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[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
C. Shut off main gas and begin prepurge timing.