Re: 25-ohms ??
Originally posted by tpwd:
posted April 08, 2003 12:36 PM thank you all for replying...we inspectors require the resistance to be 25 ohms or less no matter what you use to get there. we use an AEMC clamp-on ground resistance tester to verify this. we only accept ground rods as the last resort to ground a service. i have been asking this question for many years....no one [especially NEC code writers] will answer it. they all say the "authority having jurisdiction" [which is a phrase used to pass-the-buck] shall make the call.
if this is a safety issue, why don't we put a value on it?...if not why drive another rod if it doesn't work anyway???....thanks to all
He then added the following.
yes...all the electrical engineers that i have talked with [over 25] say they want 25-ohms or less on services?....so we enforce them...i don't know where you can't get the resistance under 25-ohms if you try, we install services in granite outcropping area and have to use a engineered design, sometimes beninite composite...but usually burying 20' of #2 copper gets the resistance down..
Long time participants here already know that inspectors who make up rules as they go along are a very sore subject with me. So they can go on to another post. For those not familiar with the legal implications of inspector conduct I offer the following.
Let me express the hope that you are either a contract compliance inspector, rather than a public agency AHJ, or that you have a locally adopted code or amendment to provide legal authority for your position. If you are ordering contractors to meet this twenty five ohm bench mark without contract or statutory authority you are engaged in the essence of arbitrary and capricious abuse of office. If your state has a state wide board of appeals a review of there decisions will reveal that if the requirement is not in a code that is adopted pursuant to statute then the inspector can only order a change based on the legal doctrine of clear and present danger. That means that if you have no code provision that requires the change you have to show that the present condition is an immediate danger to public safety. The reason that the US NEC does not require that the grounding electrode system meet a specific ground impedance value that there is no scientific or experiential basis for such a standard.
I am willing to concede that most such "field expedient corrections," on the part of public agency AHJs, are ordered in good faith by conscientious men and women who are just trying to do a good job. The problem is that such conduct reveals that the public agency that employs you has failed to provide adequate training in the application of administrative law. To tolerate public officials making up rules that they then enforce as law is to set up little tin pot gods that are acting outside the law. Such conduct will inevitably bring the entire code enforcement process into public disrepute. This is not intended as a personal attack on you but rather a statement of my belief that the enforcement of the code AS WRITTEN is the key to public acceptance and confidence in the regulatory process.
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Tom
