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rkenney

Residential Panel Grounding

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Hi group, this is my first post so please bear with me. I just got Rex Cauldwell's book "Inspecting a House" for 2.99 off E-bay. Some great illustrations for a newbie who hasn't seen much (me).

My question is this, he says (on pge. 43 if you have the book) that there needs to be a ground rod from the service panel even if the metal plumbing is grounded (bonded). This is the only place I've read this. All the houses I've done, including my own, only have one or the other. Ground rod if you have plastic (PB) water main and vice versa.

What is the correct (new code -old code ?) situation here? Should I report service entrance panels without both? I'm licensed for Maryland if region makes any difference.

www.IndependentHomeInspectionMD.com

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250.53(D) Metal Underground Water Pipe. Where used as a

grounding electrode, metal underground water pipe shall

meet the requirements of 250.53(D)(1) and (D)(2).

(1) Continuity. Continuity of the grounding path or the

bonding connection to interior piping shall not rely on water

meters or filtering devices and similar equipment.

(2) Supplemental Electrode Required. A metal underground

water pipe shall be supplemented by an additional

electrode of a type specified in 250.52(A)(2) through

(A)(7). Where the supplemental electrode is a rod, pipe, or

plate type, it shall comply with 250.56. The supplemental

electrode shall be permitted to be bonded to the grounding

electrode conductor, the grounded service-entrance conductor,

the nonflexible grounded service raceway, or any

grounded service enclosure.

So...in a modern set-up if they are using buried metallic water pipe as the main electrode, you should also see a supplemental (typically ground rod(s)). But in a house with a plastic water service you would normally see just the one type of electrode (rods or UFERs).

Many older houses around here will only have the supplemental ground rods if the panel or service has been upgraded in the last couple of decades (or so). Someone else may know when the supplemental requirement actually came into being.

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. . . Someone else may know when the supplemental requirement actually came into being.

Richard,

The requirement for a supplemental electrode came into being with the 1984 NEC. Back then, it was at 250.81(a).

(Oops, correction, Douglas pointed out that it was actually the 1978 edition.)

Bob,

Welcome to TIJ. Just because the NEC has required a supplemental electrode for the last 33 years does not mean that Maryland does. States can be slow to adopt new editions of the model codes and when they do, they can make changes to them. We have some folks from Maryland on this forum, they might know about the specific rules there.

I've also got to point out that, while Cauldwell is correct about this issue, I think you overpaid for the book. I remember looking through it when it came out. I chose three pages at random and found errors on each of the three pages. Verify everything in there before accepting it as true.

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Thanks Jim and Richard for the replies. I am a firm advocate of "measure twice and cut once," and this applies to words as well (my wife may disagree :). So I appreciate the clarification you've provided. It was worth the $2.99 simply to raise and answer the question.

I am always ready to learn although I do not always like being taught.

Winston Churchill

Bob Kenney, Maryland

www.IndependentHomeInspectionMD.com

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When I need to find area specific code and to find out what version are currently in force, I usually Google the specific county.

Example: google search "anne arundel county electrical code"

Find: http://www.aacounty.org/IP/PAC/BuildingCodes.cfm

The page shows what versions of various code apply to the various categories. This particular page for Anne Arundel County has a link to amendments in Bill 46-03 at the top of the page. It requires some scrolling but additional information can be found there.

Other counties have similar information available online.

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