Electrical and RF Safety
Safety in the ham shack: electrical shock and treatment, safety grounding, fusing, interlocks, wiring, antenna and tower safety
Which wire or wires in a four-conductor connection should be attached to fuses or circuit breakers in a device operated from a 240 VAC single phase source?
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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What is the minimum wire size that may be safely used for a circuit that draws up to 20 amperes of continuous current?
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?
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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Which of the following is a primary reason for not placing a gasoline-fueled generator inside an occupied area?
Gasoline-fueled generators should NEVER be placed in an enclosed or occupied area because the exhaust fumes emitted, especially carbon monoxide, can poison or KILL you. Take care to make sure that such equipment is well ventilated and away from any vents which may carry fumes into occupied areas.
To Remember: Would you like to sit right behind the exhaust pipe of a smoke belching diesel truck? NO!!
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Which of the following conditions will cause a Ground Fault Circuit Interrupter (GFCI) to disconnect the 120 or 240 Volt AC line power to a device?
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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Why must the metal enclosure of every item of station equipment be grounded?
It is good practice when setting up your station to make sure that you have grounded any equipment with a metal chassis. Excess voltage can be caught in the metal housing if there is a short within the equipment or wiring. Proper grounding ensures that you will not have a SHOCKING experience when you touch your equipment due to hazardous voltages on the chassis.
Hint: A "metal enclosure" houses the "chassis".
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Which of these choices should be observed when climbing a tower using a safety belt or harness?
Hint: while all these options are valid, the question specifically addresses belts.
Safety belts and harnesses are designed to stop the fall of the wearer, preventing serious injury. 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.
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.
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.
Safety gear is stringently designed and tested, and should be approved by OSHA. The materials used in a harness will degrade over time. The length of time will vary, depending on the quality of the materials. In order to be safe, do not use gear that has passed its expiration date.
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.
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What should be done by any person preparing to climb a tower that supports electrically powered devices?
Tower climbing is always risky and even more so when power is involved.
Disconnecting the ground/ungrounding would add risk because it removes a path for energy to dissipate. That rules out "All" as well.
The electric company would only be involved if they had equipment on the tower, which is not likely if you're the one climbing it.
In every case you must 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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Why should soldered joints not be used with the wires that connect the base of a tower to a system of ground rods?
Solder melts at such a low temperature compared to the incredible heat produced by a lightning strike that soldered joints would melt instantly and be destroyed. In situations where lightning strikes are more likely (like an antenna tower) ground clamps are the way to go.
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Which of the following is a danger from lead-tin solder?
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 good practice for lightning protection 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?
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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What must you do when powering your house from an emergency generator?
If you don't disconnect the incoming utility power feed, power from your generator could flow back into the utility lines. This is called backfeeding, which is usually illegal and can be dangerous to both equipment (which often assumes that power flows only in one direction) and people (for example, if they're working to restore power to a neighborhood and encounter high voltage on a utility line).
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Which of the following is covered by the National Electrical Code?
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 the following is true of an emergency generator installation?
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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