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We have a 3-Phase AC Electricity Generator (19KW) which comes with tires for ease of transportation, even though it requires a crane for lifting.

We have it installed in such a way that its main body is sitting on concrete blocks which are directly attached to the soil/earth below them without any insulation in between and the rubber tires are free.

Do we still need to connect the Ground terminal on the Generator to the earth below it? It would appear that since the terminal is connected to the body of the Generator and the Body has a direct connection to the ground by virtue of it resting on the ground itself there would not be any need for that but it was advised that the Cement blocks in between break that connection.

Edit:

We did act upon the Electrician's advice and he did ground it like he said it was supposed to. This question is just for learning how important that was.

Illustration

Image Source: http://www.deepelectric.com

Image Source: www.deepelectric.com

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    \$\begingroup\$ I think grounding is done with a long metal pole, like 3 meters, inserted deep into the ground. Or even by connecting to water pipe or something. \$\endgroup\$ – Gregory Kornblum May 5 '17 at 7:03
  • \$\begingroup\$ This a question for an electrician. It is also one of those "if you have to ask you shouldn't be fooling with it" kind of questions. Doing this wrong could get someone killed. Bad enough if the doer kills himself, worse if it kills somebody who had no idea that the doer did it wrong. Anyone in that house could be killed. \$\endgroup\$ – JRE May 5 '17 at 7:25
  • \$\begingroup\$ Thanks @JRE for your advice. I have updated the question a little \$\endgroup\$ – Hanky Panky May 5 '17 at 7:28
  • \$\begingroup\$ Read the manual or speak to the company that supplied it for the most appropriate answer. \$\endgroup\$ – Andy aka May 5 '17 at 8:21
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    \$\begingroup\$ The electrician who installed it came from that very company and he did ground it properly. I just wanted to learn why it was not already grounded \$\endgroup\$ – Hanky Panky May 5 '17 at 9:16
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By just laying the generator on the ground (concrete block) doesn't mean it is grounded. A ground shall be an electrical, low resistance connection to the earth. To provide enough low resistance, you have to bury FeZn or Cu rods into the soil.

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To properly "ground" something, it must be connected to ground via a rod to ensure a low electrical impedance to ground, simply putting it on top of the ground will not suffice due to the high impedance between the object and ground.

For example, if the outside of a box has a just a 25 ohm resistance to ground and a fault condition occurs in which 120V is put through it, you would have only 4.8 amps of fault current. This would not yield enough fault current to trip even a 20A circuit breaker.

As mentioned in the comments, definitely don't play around with stuff like this if you are not sure about what you are doing. Get a professional.

https://www.engineereducators.com/docs/groundingandbonding2-2.pdf

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