Temp Power Electrical Question

[mcelhane]

I just installed a temp power pole with a temp power box (combination box with meter, circuit breakers, and 120/240 V receptacles for providing temporary power to construction site) . I noticed as I was connecting it, that there was one "bus" bar for the ground wire from the power company and that there was a separate ground bus bar for the "true" ground from the ground rod (and the green ground wires from the receptacles). I also noticed that these two bus bars were not electrically connected. The ground line (or return line) from the power company was never really grounded to the box. Is this normal? I'm tempted to run a bare copper wire between the two "ground" bus bars, but would like some comments from you electricians out there. Thanks

[gfretwell]

They need to be bonded together.

[PipeDown]

They are sold unbonded so they you can use it as a main panel or as a subpanel (in which ground would run back to the main panel before bonding to neutral)

[volts500]

They usually come with a green bond screw to accomplish the bonding; there is a hole in the neutral bar just for it, but a wire between the neutral bar and the grounding bar will suffice.

[dnoyeB]

Ground and return are not the same thing. And what do you mean by "true" ground? How did you determine which purpose each bus bar served and that their purposes were different? Some pre-connections?

[mcelhane]

Thanks for the responses. Found the "bonding bar" that is supposed to be installed to ground the neutral from the power company to the box case. The case is already grounded by the copper wire going to the ground stake. Thanks again

[gfretwell]

One thing you need to understand. The "ground" has nothing to do with clearing a fault (tripping the breaker on a short). All of that current must go through the bonding jumper and back to the X0 centertap of the transformer. The ground rod is only there to establish a local reference for the supply, so your tools and the dirt are at the same potential. Without the bonding jumper your ground rod is nothing but a worm chaser in a fault.

[dnoyeB]

The "Ground" that comes in from the service and that is also tied to the water pipes and gas pipes, and the pole in the dirt is a safety precaution and has to do with lightning protection. It is not normally part of the circuit as no current flows into the earth, basically unless its from the sky.

The "ground" you see inside the house which is the 3rd prong is different. Its actually just a "better" return which is used under failure conditions. It is also not normally part of the circuit and it too eventually ties into the earth ground. But its purpose is not lightning protection.

[volts500]

Where is W Tom when ya want ta tim.???