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Thread: size, typed amount of grounding electrodes?

  1. #11
    Join Date
    Dec 2011
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    Wisconsin
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    447
    Quote Originally Posted by Adamjamma View Post
    actually, if it is deep enough it lowers the fault voltage... or Ze... if you cannot get it deep enough, extra ground rods bonded to eachother at a certain distance apart can help drop the voltages as well.
    I can install two ground rods connected to the grounded conductor with a 6 AWG wire and it is a compliant grounding electrode system. The resistance to ground could be 120 ohms and it would still be compliant. It would also not clear any faults. Only one amp of current would flow on a 120 volt fault and not trip a 15 or 20 amp breaker. The code only states that where a single ground rod is used, the resistance to ground must be 25 ohms or lower. Where other electrodes are used, there is no minimum resistance to ground requirement.

  2. #12
    Join Date
    Jul 2013
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    Resting under the Major Oak UK
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    1,195
    Quote Originally Posted by Adamjamma View Post
    actually, if it is deep enough it lowers the fault voltage... or Ze... if you cannot get it deep enough, extra ground rods bonded to eachother at a certain distance apart can help drop the voltages as well. Bonding is what helps keep the ground rods from introducing more problems into your residence or business due to nearby lightning strikes as well as helping clear faults a bit easier. But, ground rods do not get rid of lightning problems any more than surge protectors protect your home totally from lightning problems. A direct hit on your home is probably gonna do damage no matter what you have done to protect your home. But, proper bonding and grounding can protect your home from lightning that hits a tree two blocks away from your home.

    you want the best, lowest ground values possible so that if a fault occurs in an electrical installation, sufficient current will flow to operate the fuse or circuit breaker protecting the faulty circuit within a predetermined time. The objective is to make sure that the circuit is disconnected fast enough to prevent overheating and possibly a fire.
    You have to understand the difference between UK and US practices. The US is almost always PME, the UK has a ridiculous mix of TT, PME, TN-S, TN-C-S.

    https://www.spenergynetworks.co.uk/u...ART-01-002.pdf
    The reports of my death are greatly exaggerated.

  3. #13
    Join Date
    May 2018
    Location
    Jamaica and london
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    546
    Actually, from what I was taught, most of USA and the Caribbean use a variation of the TN-C-S system, differing in that the UK has only one phase enter the home, on one voltage, on a two wire system for TT or TN-S or a three wire for TN-C-S and then the ground is pulled from right before the meter at the home supply point inside the home. This point, in my old home and in my daughters home, has a wire that goes outside to a second ground rod, outside, and has the main earthing terminal. Us people who work on systems are not allowed to touch the supply point but there is a disconnect there for if a meter needs serviced or changed. Then you get the meter, then you go to the single phase consumers unit which at my daughters home is separated into three sections of breakers, two of which are covered by a lead RCD...
    My daughters home is a textbook of the TN-C-S system.. fairly low Ze into it.
    Homes I have worked on in Jamaica differ only in where the main ground is applied and in the lack of a disconnect before the meter, along with the extra line coming in carrying power. The wires look different but do the same thing... as it is also a TN-C-S system.

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