Training Seminars, Information and… You don’t know what you don’t know.

Wenatchee Home Inspections

Well I just got back from Las Vegas and the “Inspection Universe” conference. It was a good event for the most part (more on that later (another post?)).

Some may know that I also am now an instructor at Bellingham Technical College “Fundamentals of Home Inspection” course for those looking to get licensed in the State of Washington to perform Home Inspections.  During class I always tell the students they will need to learn a lot to really perform their job proficiently. They will also have to be careful when taking classes  or reading things on the internet that the information presented is actually correct.

When attending educational classes you need to use due diligence to ensure what you have learned is correct or fully accurate. This is tough on any presenter or teacher of the classes/seminars to ensure their material is totally accurate.  It is very easy to present something as fact when in fact it is not “fact”. We also need to vet our own preconceived idea of what is correct or what we remember.

So to the code books I go to see if I was missing something or the Instructor mis-spoke.

The information below is from the 2014 NEC.

NEC 2014 - 250.52 Grounding Electrodes

(3)Concrete-Encased Electrode.

A concrete-encased electrode shall consist of at least 6.0 m (20 ft) of either (1) or (2):

1. One or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, installed in one continuous 6.0 m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effective means to create a 6.0 m (20 ft) or greater length; or
   (2) Bare copper conductor not smaller than 4 AWG.

Metallic components shall be encased by at least 50 mm (2 in.) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or within vertical foundations or structural components or members that are in direct contact with the earth. If multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

Informational Note: Concrete installed with insulation, vapor barriers, films or similar items separating the concrete from the earth is not considered to be in “direct contact” with the earth.

Now to the section on supplemental electrodes-

NEC 2014 - 250.53 Grounding Electrode System Installation

(2)Supplemental Electrode Required.

A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:

(1)Rod, pipe, or plate electrode

(2)Grounding electrode conductor

(3)Grounded service-entrance conductor

(4)Nonflexible grounded service raceway

(5)Any grounded service enclosure

Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.

So the code states that if you have a rod, pipe or plate electrode it must be supplemented unless you can prove the electrode has a resistance of 25 ohms or less.  No where is there such a requirement for Concrete Encased Electrodes (CEE), which I thought, since they have a very low resistance.

Dr Uer developed this electrode system because the military required low-resistance (5 ohms or less) ground connections for lightning protection systems of its ammunition and pyrotechnic storage sites in Arizona.

Ufer’s test results which was conducted over a 20 year period showed that the CEE’s had a resistance value of 2 to 5 ohms. ( More on CEE ). Since this is way below the 25 ohm threshold it would not require any supplementary electrodes.

Washington state requires the use of the CEE (with exception) effective 3/1/13

From the Washington Administrative Code (WAC)

WAC 296-46B-250

052 Grounding electrodes.

(2) Except for mobile/manufactured homes, a concrete encased grounding electrode must be installed and used at each new building or structure that is built upon a permanent concrete foundation. The electrode must comply, with NEC 250.52 (A)(3). Inspection of the electrode, may be accomplished by the following methods:

(a) At the time of inspection of other work on the project, providing the concrete encased electrode is accessible for a visual inspection;

(b) At the time of the service inspection providing the installer has provided a method so the inspector can verify the continuity of the electrode conductor along its entire length, with a minimum twenty foot linear span between testing points (e.g., attaching a length of copper wire to one end of the electrode that reaches the location of the grounding electrode conductor that will enable the inspector to measure the resistance with a standard resistance tester). The concrete encased electrode does not have to be accessible for a visual inspection; or

(c) Other method when prior approval, on a job site basis, is given by the inspector.

If a special inspection trip is required to inspect a grounding electrode conductor, a trip fee will be charged for that inspection in addition to the normal permit fee.

Exception:

If the concrete encased grounding electrode is not available for connection, a ground ring must be installed per NEC 250 or other grounding electrode installed per NEC 250 verified to measure 25 ohms or less to ground. Resistance verification testing must be performed by an independent firm having qualified personnel and proper equipment. A copy of the testing procedures used and a written resistance test record signed by the person performing the test must be available at the time of inspection. The resistance test record must include test details including, but not limited to, the type of test equipment used, the last calibration date of the test equipment, and all measurements taken during the test.

“Codes are minimum standards and most houses are built by the lowest bidder”

Don Hester

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

www.ncwhomeinspections.com                                                   509-670-9572

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