Investigation and Test of Grounding Method for Electrical Installations

This article was posted 02/22/2008 and is most likely outdated.

Topic - Interesting and Important Documents
Subject - Investigation and Test of Grounding Method for Electrical Installations

February 22, 2008
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Interesting and Important Documents

Investigation and Test of Grounding Method for Electrical Installations

This is the first in a new series we’re starting in which we’ll send you interesting and important documents from Mike Holt’s archives.

This paper written by H.G. Ufer in 1961 explores the need for an adequate means for grounding. One which requires very little maintenance and one which does not require connection to the water pipe systems to provide an adequate low resistance ground. The purpose of this paper was to record the development and test of such a grounding method and to suggest its further test.

Click here to read the entire paper.

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Comments

Maryland requires that the foundation rebar be used as the grounding. Since it is a requirement, the foundation contractor leaves a stub of rebar sticking out of the foundation near the service entrance.

I was troubleshooting one house where the microwave and stove controls were erratic.

The owner had watched the building process and stated that the house had two layers of poly sheeting under the basement floor slab and foundation. The rebar was entirely inside the concrete, not stuck in the soil.

When the ground was tested, it was found to be almost 300 ohms. The electrical contractor added a ground rod which dropped the resistance to around 30 ohms. While it did not meet NEC and there were several amperes flowing on the ground the AHJ did not require any additional grounding.

The utility then made some modifications to the transformer in the yard (perhaps secured the neutral) and the problems cleared.

The owners' now have a very dry basement and working microwave and stove controls.

Tom

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