Grounding electrodes vs Voltage drop

[dfmischler]

the one thing I am struggling with is whether or not to drive a ground rod as an adjunct to the ground coming from the panel with the power. the hoop house is comprised od tubular pipe set in the earth so i'll bond that but I wonder if that is sufficient?

500' from the panel seems like a long way to expect there to be no ground potential differences. I might be concerned for workers safety working on a (wet) dirt (or concrete) floor without a nearby ground (I know GFCIs don't need it). How deep in the ground is the tubing set? The tubing on the hoop house I have here is set in concrete about 4' deep, but it is only about 100' from the service entrance (6 other greenhouses of varying types and sizes, mainly glass).

 

[kwired]

If you are concerned with voltage drop and how it effects GFCI operation - the EGC should not be carrying any current except during abnormal fault conditions - no current = no voltage drop, on the EGC.

If you have significant voltage drop on the normal current carrying conductors, remember for a simple two wire circuit, if they are same size and type only half of that drop is on the ungrounded supply conductor and the other half is on the grounded return conductor, this does raise your voltage to ground some, but the amount necessary to effect the 4-6 mA trip threshold of a GFCI is almost something you can disregard. If you have 112 volts instead of 120 to "ground" because of voltage drop, the fault conditions necessary to trip the GFCI are nearly unchanged.

 

[ActionDave]

I spun these two posts off from the original thread to their own because they are more philosophical than practical but should be good discussion points.