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swapan mukherjee
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Earth Pit

05/12/2016 2:35 PM

What should be minimum resistance for individual pits as per IS /BS/IEEE?
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SolarEagle
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#1

Re: Earth Pit

05/12/2016 2:53 PM

Minimum resistance would be adequate for intended use....

http://electrical-engineering-portal.com/how-to-determine-correct-number-of-earthing-electrodes-strips-plates-and-pipes-part-1

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Tornado
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#2

Re: Earth Pit

05/12/2016 4:26 PM

The minimum would be zero ohms; what you need to know is the maximum allowable.

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Anonymous Poster #1
#3

Re: Earth Pit

05/12/2016 7:38 PM

Before this happens!

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brich
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#4

Re: Earth Pit

05/12/2016 10:58 PM

As you know about " IS /BS/IEEE" why have you not looked it up?

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PWSlack
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#5

Re: Earth Pit

05/13/2016 3:29 AM

The maximum allowable resistance is that which ensures reliable operation of the circuit protective device(s) for the installation, about which the forum knows nothing as the information has been withheld from it.

If in doubt, consult a qualified local Electrician.

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TonyS
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#6

Re: Earth Pit

05/13/2016 5:17 AM

Unfortunately finding a recommended maximum isn't easy. BS7671 is so ambiguous that many misinterpret it. NFPA-NEC isn't much better. The only definitive figure I've seen is in supply company documentation.

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James Stewart
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#7

Re: Earth Pit

05/13/2016 2:01 PM

There is a rule of thumb. If your thumb placed on the ground during ground fault senses a shocking value of potential, then you need a lower earthing ground resistance value.

There are things to be done in addition to providing more plates and bars. Use the correct fill material for the grounding hole, include some form of carbon that has a reasonable value of conductivity, and maintain at least the minimum specified level of ground electrolyte/water to maintain soil conductivity.

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TonyS
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#8
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Re: Earth Pit

05/14/2016 4:41 AM

Bentonite is excellent as an excellent electrolyte for earth rods. I don't know about cost, we used it as part of the process so if I needed some I just helped myself.

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coolyaar
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#9

Re: Earth Pit

05/22/2016 6:40 AM

resistance of a single ground rod in a pit should not be greater than 25 ohm as per NEC code. however the overall earthing resistance of your system depends on following three parameters :

i: maximum allowable touch voltage 2: maximum allowable step voltage 3: maximum expected earth fault current.

your earthing resistance should be such that it does not cause step and touch voltages above limit values during occurance of maximum earth fault current.
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7anoter4
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#10

Re: Earth Pit

01/27/2017 5:01 AM

I am sorry. Since it is so much superstition [stupidity] around a few very known and respectable standards as IEEE 80/2000 and other I should avoid to express any new think.

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