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Old 15-Jan-2015, 2:27 AM   #5
GroundUrMast
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Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,773
Most areas of the country use the NEC as the basis of their electrical code. However, each jurisdiction can implement local variations as they see fit. In my area, each separate building on a property is required to have one or two ground rods if there is a service or sub-panel in or on the building. I have two outbuildings that are served by sub-panels. Because the soil conductivity is poor, each building is equipped with two 8' ground rods spaced 6' or more apart.

Not many years ago, the code only required that a sub-panel be connected to main service via a grounding conductor, a neutral conductor that is isolated from the ground except at the main service panel and an appropriate number of phase (hot) conductors. Back then, no rod was required at the outbuilding... My understanding is that the addition of a rod was to increase the protection of each buildings electrical system from lightning induced fault current and reduce the fault current conveyed to the main or adjacent buildings.

So currently, this usually means a total of four conductors are needed for a single phase 120/240 sub-panel feed. The only place that the neutral and ground should be bonded together is in the main service panel. Bonding the ground and neutral elsewhere, including the sub-panel can lead to unintended current flow in the ground conductors. In the worst case, mixing neutral and ground together can set up a lethal condition if the neutral conductor is broken or a splice/connection goes bad. As much as 120VAC could appear on the frame of equipment that you think is grounded.

As I look at the photo of your panel, I don't see a ground conductor and it appears that the neutral is bonded to the frame of the panel. I would add a #6 AWG ground conductor in the run from the main service and terminate it on the left 'ground' bar... leaving the bonding strap between the panel and bar connected. I would move all branch circuit ground conductors to the left 'ground' bar. I would also use the right 'neutral' bar for branch circuit neutrals only and would disconnect the bonding strap from the right hand 'neutral' bar to prevent normal neutral current from finding a secondary path to ground... All normal neutral current should return to the main service via the neutral conductor. Ground conductors should never carry normal current, they are there to carry fault current if the need arises.

Finally, I'd add at least one 8' ground rod near the sub-panel and connect it using #6 AWG to the 'ground' bar in the sub-panel. I would then ground my antenna mast and coax via a connection to the ground bar outside the building.

http://forum.tvfool.com/showthread.php?t=901 (post #20 is a general antenna system grounding summary)
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Last edited by GroundUrMast; 15-Jan-2015 at 2:38 AM. Reason: sp
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