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Old 2-Dec-2013, 9:45 PM   #21
teleview
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changing methods

+=>
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The changing thinking and information and the "Correctness" of grounding.

There is and was a time when separate ground rods were the Correct action.

There is and was a time when cold water pipes were the correct action to take.

There is and was a time when connecting to the electric service ground was a Big No , do not do it.

The Correct thinking changes over time.
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Old 2-Dec-2013, 10:38 PM   #22
GroundUrMast
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Quote:
There is and was a time when separate ground rods were the Correct action.
Yes, then it was realized that fault current flowing in one grounding system could raise the voltage to dangerous levels relative to the separate ground system. So the current codes call for bonding to prevent dangerous voltage differences from occurring.

Examples:
Quote:
250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

FPN: An important consideration for limiting the imposed voltage is the routing of bonding and grounding conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

(NEC - 2008 edition)
Quote:
There is and was a time when cold water pipes were the correct action to take.
Yes, and in the case of metal pipe that is buried in earth for 10' or more, that is still a grounding electrode and needs to be bonded to any other grounding electrodes.

Example:
Quote:
250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

(NEC - 2008 edition)
Quote:
There is and was a time when connecting to the electric service ground was a Big No , do not do it.
Perhaps you can cite examples of that... was that an old version of the NEC, a local interpretation/modification by a city or state or a lay persons opinion?
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