Wiring question

[NIdaho]

Hey folks,

Yes should have only 1 (one) Neutral to Ground Bond and that should be at the Main Panel or Service disconnect switch or meter (but not at all 3).

Whether to drive another ground rod or connect to the rebar or mesh in the concrete? You will probably get a better ground (lower impedance to ground) by connecting to the Rebar or mesh. Concrete is conductive and actually makes a pretty good ground system (usually better than a couple of 8' rods). The Concrete Encased Ground Electrode or Ufer Ground (named after the guy that researched them for the Army back in the 50s?) has been found to provide much better grounds than other methods for certain soil conditions.

NEC (National Electric Code) now calls for all sub panels to be fed with 4 wires (Hot-Hot-Neutral and Ground) and you need to make sure that the Neutral and Ground are separated at the sub-panel(s) (remove the bonding screw or strap). Barns (if I remember correctly) have some unique grounding requirements under the code as stock can feel ground potential diffences that people can not (front and back feet are separated by a distance and so they pick up more of the voltage/potential difference than we can -- unless you can separate your feet that far), not to mention that most barns have manure/mud mixtures in or near them that are very conductive.

Let me know if you have further questions.

 

[SPIKER]

Hi Cal:

Yes using the Extension cord to check your Neutral resistance from Barn to House is OK, just make sure you kill the power first Take a reading of the Neutral in the Extension cord to get a base reading for that length of wire only (probably an OHM or two at most for a 100' of GOOD cord.)

Someone mentioned that Concrete is a good ground (a broad statement as all concrete is different and install conditions vary.) It is hard to know if there was/were / is Styrofoam for instance under the concrete which is a good insulator.
I suggest tying the Mesh to a 8' Ground Rod at the same point as the Panel Ground.

New systems does require 4 wire installs unless it is a Service entrance install. again wide ranging statement that is not applicable to your OLD system.

If you have OTHER building done the same way then I would follow the same instructions as previously BOND Neutral to Ground at the MAIN panel. If you have separate services from your meter base to these different buildings then you can run the 3 wire USE (underground Service Entrance cable) from the meter base to the building then bond this MAIN panel to ground and drive a good ground and or have perimeter footer grounds as NEC seems to like better than a single ground rod. I would suggest going to the library and checking the NEC out look under "Service-Entrance Cable." and section 250.*** Grounding for more info.

Mark