Farm service ground arangement

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hey_poolboy

hey_poolboy

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Illinois
Most of what I have experience in is reisdential, but I am looking at a job for a friend involving a farm service. I would be 400A single phase service drop on a yard pole. My plan is to run to two 200A d-con's (one for house one for machine shed)The disconnects would be at the yard pole and I am not sure what the best way to arrange my grounding is.

i.e. electrodes at yard pole and at buildings?
4 wire to buildings since past service
disconnect, etc.
 
Re: Farm service ground arangement

A grounding electrode system is required at each structure and at the service pole.

The code gives you the option to run either a three wire or four wire system to the separate buildings. See section 250.32 for specifics.
 
Re: Farm service ground arangement

A four wire would be better due to return current threw earth instead of a wire that is how you get a voltage on metal tie stalls ect..
 
Re: Farm service ground arangement

I tend to agree. There will always be some current flow through the grounding electrode system. By providing a 4-wire system, the grounded conductor bond is not made and no normal operation current will flow except exclusively over the insulated system. A 3-wire system requires the bond which would then result in some current flowing through the grounding electrode system and Earth back to the service. This could be hazardous to animals.
 
Re: Farm service ground arangement

Thanks for the info guys.
I plan to run the 4 wire system anyway. I do have one question though. If I have to put a GEC at the yard pole should I do a #4 from each d-con, or do a 1/0 at the meter.
 
Re: Farm service ground arangement

If the GEC is going to be a driven electrode, The code only requires a #6 to the electrode if it does not go to another type of electrode that requires a larger wire.

250.66(A)
Connections to Rod, Pipe, or Plate Electrodes. Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or 250.52(A)(6),that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.
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Bold by me.

[ January 04, 2005, 12:50 AM: Message edited by: hurk27 ]
 
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