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Old 02-06-2011, 07:29 PM   #16
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Proper way to ground a subpanel


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True or false? Ground rods are not required with a ufer ground.
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Old 02-06-2011, 08:27 PM   #17
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Proper way to ground a subpanel


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Old 02-06-2011, 09:27 PM   #18
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Proper way to ground a subpanel


Let's suppose you have an appropriately sized ground wire accompanying the hot and neutral feed passing through the nipple that connects a subpanel to a main panel. The ground wire is attached to the ground bus in each panel. The ground bus in each panel is attached to the panel itself. Therefore the two panels are now bonded to one another and it is not necessary to use any special kind of clip or lug at the nipple, no?

Or let's say the nipple joining two panels was really well attached using bonding bushings, lock washers, etc. The panels are now bonded and their respective ground busses are also bonded by being fastened to the panels. So no ground wire need accompany the feed wires through the nipple, no?

The steel reinforcing bars in concrete (a Ufer ground) are recognized collectively as a grounding electrode. But I question how effective it is when the bonding happens to be made to a short piece of rebar that was wired not that tightly to other adjacent or sistered or crossing rebars and the fact the rebar bonded to was short was not visible given that most of the rebar remained concealed in the concrete.
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Old 02-06-2011, 09:47 PM   #19
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Proper way to ground a subpanel


A grounding bushing or a grounding lock nut may be required depending upon the circumstances. Inductive reactance could cause the nipple to act as a choke.
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Old 02-06-2011, 10:45 PM   #20
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Proper way to ground a subpanel


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The steel reinforcing bars in concrete (a Ufer ground) are recognized collectively as a grounding electrode. But I question how effective it is when the bonding happens to be made to a short piece of rebar that was wired not that tightly to other adjacent or sistered or crossing rebars and the fact the rebar bonded to was short was not visible given that most of the rebar remained concealed in the concrete.
I thought the concrete acted as a conductor as well, not just the rebar?
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Old 02-07-2011, 10:48 AM   #21
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Proper way to ground a subpanel


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Let's suppose you have an appropriately sized ground wire accompanying the hot and neutral feed passing through the nipple that connects a subpanel to a main panel. The ground wire is attached to the ground bus in each panel. The ground bus in each panel is attached to the panel itself. Therefore the two panels are now bonded to one another and it is not necessary to use any special kind of clip or lug at the nipple, no?

Or let's say the nipple joining two panels was really well attached using bonding bushings, lock washers, etc. The panels are now bonded and their respective ground busses are also bonded by being fastened to the panels. So no ground wire need accompany the feed wires through the nipple, no?

The steel reinforcing bars in concrete (a Ufer ground) are recognized collectively as a grounding electrode. But I question how effective it is when the bonding happens to be made to a short piece of rebar that was wired not that tightly to other adjacent or sistered or crossing rebars and the fact the rebar bonded to was short was not visible given that most of the rebar remained concealed in the concrete.
That would not be a proerly installed concrete encased electrode.
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Old 02-12-2011, 02:47 PM   #22
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Proper way to ground a subpanel


Refresh - I'm adding 120V 60A SquareD sub-panel with a generator lockout (comes with the panel) between a 60A main and 30A "from generator" breaker that came in the panel. The existing circuits I want to move to the sub panel are all 120V, no 240V circuits, so the panel will have the same 120V phase on both rails. There's a lug on each rail in the new panel that will allow me to tie them together with #8.

When I move the existing circuits to the sub panel, do I have to move their neutrals and equipment grounds?

The (higher priced) generator transfer panels from reliance, etc. just run the hot (two per circuit - one from existing breaker and one from switch in transfer panel). Yet I thought code required a conduit to carry both conductors for a circuit. So I see three options:
1. For each existing circuit, move all three wires - hot, neutral & equipment ground to the subpanel (most work)
2. For each existing circuit, move just the hot wire to the subpanel and leave the circuit's neutral and equip ground in the main panel (sounds wrong but easy)
3. For each existing circuit, move the hot and neutral to the subpanel but leave the equp ground in the main panel (better than moving all 3 conductors per circuit)

What's the most correct option?

Lastly, I thought splices in a circuit's hot conductor inside the main panel are frowned upon (prohibited?). Yet the generator transfer switches (reliance, etc) all work that way, splicing the wire from the transfer switch to the circuit. If I'm doing this via a subpanel, is a splice acceptable (in case some of the circuit's conductors aren't quite long enough to route neatly to the subpanel)?

W.R.T. grounding - I'll just be running 3 #8 conductors - 120 via a 60A breaker in the main, neutral from the neutral bar in the main panel to the (isolated) neutral in the subpanel, and equip ground from the main panel. I need to buy a small bar for the equip ground in the subpanel.

Thanks.
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Old 04-01-2011, 08:09 PM   #23
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Proper way to ground a subpanel


So the bottom line from all that is that 2 ground rods are required to be connected to the isolated ground side of a subpanel in a detached structure, Also, any copper plumbing and metal conduits need to be connected to the isolated ground side of the subpanel. Did i follow all that right?
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Old 04-01-2011, 11:45 PM   #24
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Proper way to ground a subpanel


There is NO "isolated ground" in a residential sub-panel. The ground is bonded to the panel enclosure, the neutral is not.
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Old 04-02-2011, 10:48 AM   #25
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Proper way to ground a subpanel


ok, isolated from the neutral. The ground bar on one side of the subpanel accepts all the neutrals from the circuit breakers, and the bar on the other side gets all the bare grounds and the wires bonding the water pipe and metal conduit, and connects to the ground rods outside. The two sides are separate in the panel with the connector removed in the subpanel. Do i have it this time?
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Old 04-03-2011, 11:22 AM   #26
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Proper way to ground a subpanel


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ok, isolated from the neutral. The ground bar on one side of the subpanel accepts all the neutrals from the circuit breakers,
You start by calling it a neutral, then a ground bar, and then you connect neutral so...
Why not just call it the neutral bar or neutral bus? It is less confusing.

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