I was troubleshooting a control board for irrigation. I noticed a ground rod driven below it and a #6 bare solid copper conductor ran to it. They said that was required there for lighting protection and if removed would void warranty. Is there a problem with this. It seems to me that if there is a fault that it would create a parallel path back to the source. I really don't see a problem with this because current is looking for the least resistive path. What are you thoughts.
Lighting protection
- Thread starter JdoubleU
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Cow
Senior Member
- Location
- Eastern Oregon
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- Electrician
Supplemental electrodes are used all the time. Detached buildings, irrigation center pivots, light poles are a few examples.
- Location
- New Jersey
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- Journeyman Electrician
As Cow mentioned, these were once called supplementary electrodes and are now called Auxiliary Grounding Electrodes as permitted and outlined in 250.54. Parallel paths are permitted for EGC's and current would flow on all parallel paths regardless of their resistance. Here's one older example:
electricmanscott
Senior Member
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- Boston, MA
What type of lighting are you protecting?
gar
Senior Member
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- Ann Arbor, Michigan
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- EE
090805-0648 EST
infinity:
What is the purpose of the Supplemental Grounding Electrode in the illustration shown?
The subtitle is Signal Reference Ground. What was the intended purpose of this subtitle?
For low level signals such as RS-232 I would suggest that such a ground reference is not a good solution and may not effectively solve noise problems.
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infinity:
What is the purpose of the Supplemental Grounding Electrode in the illustration shown?
The subtitle is Signal Reference Ground. What was the intended purpose of this subtitle?
For low level signals such as RS-232 I would suggest that such a ground reference is not a good solution and may not effectively solve noise problems.
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ItsHot
Senior Member
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- A little piece of heaven!
Scott you had to say it,didn't you!:smile:
electricmanscott
Senior Member
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- Boston, MA
Come on, somebody had too. :grin:
Even thought this is posted in the grounding versus bonding forum. (By the way, you'd think one of them would have won by now).....
It's kind of funny. People always put lighting questions in the lightning forum. In this case we have a question that appears to actually be about lightining and it is spelled lighting, twice. Too funny. :smile:
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
MYTH BUSTER ALERT!
current does not take the path of least resistance!
it takes all paths back to it's source
weressl
Esteemed Member
MYTH BUSTER ALERT!
current does not take the path of least resistance!
it takes all paths back to it's source
Not exactly a myth.
Most current take the path of the least resistance.
- Location
- New Jersey
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- Journeyman Electrician
- Location
- Illinois
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- retired electrician
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090806-0915 EST
A supplemental ground rod at a machine in addition to the EGC may slightly reduce a ground noise problem, but in most cases is not an adequate solution. It in no way solves the problem of a hot wire short to the equipment chassis that produces a voltage on the chassis of about 1/2 the hot source voltage relative to the EGC connection point in the main panel.
A ground rod only connection at a machine, meaning no EGC connection, an NEC violation and a true safety problem, may or may not have any effect on a ground noise problem.
Another scheme, again an NEC and real safety problem, is to float a computer off of its EGC and use the RS232 cable common to reference the computer chassis to the machine chassis. This may solve the noise problem, but creates the safety problem.
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A supplemental ground rod at a machine in addition to the EGC may slightly reduce a ground noise problem, but in most cases is not an adequate solution. It in no way solves the problem of a hot wire short to the equipment chassis that produces a voltage on the chassis of about 1/2 the hot source voltage relative to the EGC connection point in the main panel.
A ground rod only connection at a machine, meaning no EGC connection, an NEC violation and a true safety problem, may or may not have any effect on a ground noise problem.
Another scheme, again an NEC and real safety problem, is to float a computer off of its EGC and use the RS232 cable common to reference the computer chassis to the machine chassis. This may solve the noise problem, but creates the safety problem.
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