Ground Rod Myth Video

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ruko

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Mr. Holt's video about the myths of grounding rods is enlightening and informing. I look at this in an entirely different way now. Good to know. If say 4 ground rods were used each having the equivalent of 25 ohms resistance back to the source would the resistance be 6.25 ohms? This would trip a 15 amp breaker easily on a 120 volt circuit. I believe the resistances would have to be considered in parallel. A grounding conductor is of course the most sensible way to ground equipment or, as in the case of the video, a lamp pole.

Thanks very much for that video.
 

GoldDigger

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ruko, if the ground rods are far enough apart to be outside the spheres of influence of the other rods, then you can add the resistances in parallel.
 

iwire

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If say 4 ground rods were used each having the equivalent of 25 ohms resistance back to the source would the resistance be 6.25 ohms? This would trip a 15 amp breaker easily on a 120 volt circuit.

Ruko, 120/6.25=19.2 amps.

For what it is worth that will not easily trip a 15 amp breaker. If it trips at all it will take a number of minutes.

You need something in the range of 60 -70 or more amps of current to cause a instantaneous trip.
 

ruko

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Ground Rod Myth Video

Ruko, 120/6.25=19.2 amps.

For what it is worth that will not easily trip a 15 amp breaker. If it trips at all it will take a number of minutes.

You need something in the range of 60 -70 or more amps of current to cause a instantaneous trip.

Good point. Forgot about the built in delay. Looking at the tripping curves on some breakers, at 19 amps it will take a while to open.
 

don_resqcapt19

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The standards for both breakers and fuses would permit a 15 amp rated device to carry 20.1 amps forever without tripping. At 20.25 amps the device must open the circuit in one hour or less.
 

mbrooke

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Mr. Holt's video about the myths of grounding rods is enlightening and informing. I look at this in an entirely different way now. Good to know. If say 4 ground rods were used each having the equivalent of 25 ohms resistance back to the source would the resistance be 6.25 ohms? This would trip a 15 amp breaker easily on a 120 volt circuit. I believe the resistances would have to be considered in parallel. A grounding conductor is of course the most sensible way to ground equipment or, as in the case of the video, a lamp pole.

Thanks very much for that video.


Still, a bonding jumper does far better. I have no idea who these ground rod myths came up. I see so many grounding and bonding violations yet all the concern there is exists on ground rods which do little if anything.
 
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