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Subelement G0

ELECTRICAL AND RF SAFETY

Section G0B

Station safety: electrical shock, grounding, fusing, interlocks, and wiring; antenna and tower safety

Which wire or wires in a four-conductor 240 VAC circuit should be attached to fuses or circuit breakers?

  • Correct Answer
    Only the hot wires
  • Only the neutral wire
  • Only the ground wire
  • All wires

Only fuse the HOT wires! Installing fuses on the other lines will not let excess or shorted voltage run to ground. Excess voltage would then remain in your equipment as a shock hazard.

Fusing HOT wires keeps the system COOL, fusing COOL wires keeps the system HOT! OUCH!

The answer of "Only the two wires carrying voltage" is written incorrectly. The answer choices should read:

A. Only the ungrounded conductors (the "hot" wires) B. Only the grounded conductor (the neutral wire) C. Only the grounding conductor D. All of the wires

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According to the National Electrical Code, what is the minimum wire size that may be used safely for wiring with a 20-ampere circuit breaker?

  • AWG number 20
  • AWG number 16
  • Correct Answer
    AWG number 12
  • AWG number 8

Use at least AWG number 12 wire as the minimum size for a 20-amp circuit, as this wire is rated to safely handle greater than 20 amperes of maximum current load.

Silly hint: The two most common shotgun sizes are "12" and "20" gauge.

For more on AWG wire here's a link to Wikipedia: Tables of AWG wire sizes

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Which size of fuse or circuit breaker would be appropriate to use with a circuit that uses AWG number 14 wiring?

  • 30 amperes
  • 25 amperes
  • 20 amperes
  • Correct Answer
    15 amperes

Using a 15A fuse or circuit breaker with a circuit using AWG #14 wiring will protect the wire from exceeding its maximum allowable current.

Silly hint: of the options, the number 15 is the closest to the number 14 in the question.

For more on AWG wire and maximum ampacity (current) here's a link to Wikipedia: Table of AWG wire sizes

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Where should the station’s lightning protection ground system be located?

  • As close to the station equipment as possible
  • Correct Answer
    Outside the building
  • Next to the closest power pole
  • Parallel to the water supply line

The terminations on the wires and cables for your ground system have a high resistance and therefore have the highest potential for overheating and/or exploding from an overcurrent situation such as a lightning strike. Running as many terminations as possible outside Will minimize the risk of the bodily or equipment damage inside the structure.

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Which of the following conditions will cause a ground fault circuit interrupter (GFCI) to disconnect AC power?

  • Current flowing from one or more of the hot wires to the neutral wire
  • Correct Answer
    Current flowing from one or more of the hot wires directly to ground
  • Overvoltage on the hot wires
  • All these choices are correct

A GFCI outlet measures the power coming in and then returning to your panel as it completes the circuit. It was designed to detect any difference of more than 4 or 5 milliamps and to react quickly (less than one-tenth of a second) to shut down any circuit out of this small range. Shorts will also cause this but the primary function is to measure what is going out versus what is coming back (hot/neutral).

The word "ground" is in both the question and the answer.

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Which of the following is covered by the National Electrical Code?

  • Acceptable bandwidth limits
  • Acceptable modulation limits
  • Correct Answer
    Electrical safety of the station
  • RF exposure limits of the human body

The NEC or National Electrical Code sets the US standard for wiring and electrical equipment installations (including electrical safety inside the ham shack). The NEC publishes code books and references with guidelines for safe electrical installations and practices.

See also Wikipedia: National Electrical Code

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Which of these choices should be observed when climbing a tower using a safety harness?

  • Always hold on to the tower with one hand
  • Correct Answer
    Confirm that the harness is rated for the weight of the climber and that it is within its allowable service life
  • Ensure that all heavy tools are securely fastened to the harness
  • All these choices are correct

Safety belts and harnesses do not prevent a fall, but are designed to stop the fall of the wearer, thus limiting or preventing serious injury. In order to accomplish this, the gear must be capable of halting the weight of the person wearing it, along with the weight of any other gear that may be attached to the person or harness.

Safety gear is stringently designed and tested, and should be approved by OSHA. Belts and harnesses perform two different functions, and both should be considered if climbing more than four feet above the ground unless other certified platforms are provided. Any gear attached to the harness should be attached at the provided attachment points. All OSHA approved gear is rated to handle a maximum weight, to include the person wearing it and any tools or gear the person has, and exceeding this weight risks the failure of the fall protection gear.

Also, the materials used in a harness will degrade over time. The length of time will vary depending on the materials the gear is made of. So, in order to be safe, do not use gear that has passed its expiration date.

The ratings and limitations of the gear are found on a label attached to the gear. This label should never be removed, and should be legible.

Any fall protection device that has, in the past, arrested a fall, or that is frayed or damaged, or that is missing the label, or is past its expiration date, should be destroyed in a manner that it can no longer be used, and discarded appropriately.

Hint: while all these options are valid, the question specifically addresses belts.

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What should be done before climbing a tower that supports electrically powered devices?

  • Notify the electric company that a person will be working on the tower
  • Correct Answer
    Make sure all circuits that supply power to the tower are locked out and tagged
  • Unground the base of the tower
  • All these choices are correct

Tower climbing is always risky and even more so when power is involved.

Make absolutely sure that all circuits that supply power to the tower are totally DISCONNECTED, LOCKED OUT and TAGGED OUT (LOTO). This is so that someone below who does not know that you are on the tower will see the tagged circuits and know to NOT reconnect the power.

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Which of the following is true of an emergency generator installation?

  • Correct Answer
    The generator should be operated in a well-ventilated area
  • The generator must be insulated from ground
  • Fuel should be stored near the generator for rapid refueling in case of an emergency
  • All these choices are correct

Emergency generators, especially those fueled by gasoline or diesel, must always be located in well ventilated areas. Inside a garage, basement or other occupied location are NOT good places for such equipment as harmful exhausts, especially carbon monoxide can poison or KILL you.

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Which of the following is a danger from lead-tin solder?

  • Correct Answer
    Lead can contaminate food if hands are not washed carefully after handling the solder
  • High voltages can cause lead-tin solder to disintegrate suddenly
  • Tin in the solder can “cold flow,” causing shorts in the circuit
  • RF energy can convert the lead into a poisonous gas

Lead can contaminate food if hands are not washed carefully after handling the solder.

Lead is known to be a toxic substance, and so contact with skin and especially foods should be avoided. Wear gloves when possible and make sure to wash your hands thoroughly after using solder, especially before eating.

It is also good practice to never eat at your work bench – you don't know what chemicals or hazards you might pick up with your sandwich!

Tin whiskers only in lead free solder

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Which of the following is required for lightning protection ground rods?

  • They must be bonded to all buried water and gas lines
  • Bends in ground wires must be made as close as possible to a right angle
  • Lightning grounds must be connected to all ungrounded wiring
  • Correct Answer
    They must be bonded together with all other grounds

It’s important to bond all of your grounds lines together (shack and house, etc.) so that in case of a lightning strike current cannot jump from one ground to another causing destructive surges.

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What is the purpose of a power supply interlock?

  • To prevent unauthorized changes to the circuit that would void the manufacturer’s warranty
  • To shut down the unit if it becomes too hot
  • Correct Answer
    To ensure that dangerous voltages are removed if the cabinet is opened
  • To shut off the power supply if too much voltage is produced

Interlock circuits are intended to provide safety by preventing you from coming into contact with components of your equipment which may have dangerous voltages.

The interlocks ensure that dangerous voltages are removed if you open the equipment cabinet.

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Where should lightning arrestors be located?

  • Correct Answer
    Where the feed lines enter the building
  • On the antenna, opposite the feed point
  • In series with each ground lead
  • At the closest power pole ground electrode

In the event of a lightning strike nearby, the lightning arrestor conductors can carry very high fault current levels. These high currents do have a risk of causing fire or shock, depending on installation effectiveness, as such, arrestors are located outside of the dwelling. We do want all outside conductors protected from lightning induction voltages as well, therefore we want arrestors as close to dwelling as possible.

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