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Old 09-09-2011, 08:20 PM   #1
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sub panel wiring


I'm getting ready to run 6/3 wire from my main panel out to a shed with a sub panel that was already installed but not wired when I bought the place. This sub panel, made by Siemens circa 1995, has no lugs on the hot bus's to hook the hot wires to. It seems like all panels I've seen pictured on you tube videos and other places on the internet have lugs joined to these hot bus bars. Instead, there is a 100 amp circuit breaker at the top of the bus bar with several 15 and 20 amp bars below it. Presumably I hook the wires into this 100 amp circuit breaker and it electrifies the whole bar? Explaining this to an employee at Home Depot who I was told was a master electrician said this should work, though he had never seen a panel like that. Has anybody out there seen this configuration and can confirm it works like that? I'm putting a 60 amp breaker in at the main panel to carry this current on the 6/3 wire, is it OK to use the 100 amp breaker the subpanel came with, or do I need to downsize it to 60 amps at the sub panel as well? And one last question, I know the neutral bus and ground bus are to be separated... I removed the bonding bar, but the green bonding screw that was sitting at the bottom of the panel unscrewed doesn't seem to fit anywhere so can I tuck a piece of copper wire from the grounding bus under a screw that mounts the panel to the wall to ground it (I also will be running a wire from the grounding bus down to a ground rod)? Thanks for any answers you can give.

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Old 09-09-2011, 09:57 PM   #2
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sub panel wiring


backfeeding a breaker is common, new codes require a 'hold down kit' when doing this with a stab in/plug on breaker.

the 100A in the sub is fine, it's just a disconnect.

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Old 09-09-2011, 09:59 PM   #3
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sub panel wiring


It sounds like you have a standard main breaker panel. Connecting the two hot legs to the breaker will energize the buss below. Post a pic to confirm this.

You might need to add a auxillary ground buss for the conductor to the rod and the ground wires from the circuits. You will also land the ground wire from the feeder on this bar.
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Old 09-09-2011, 10:34 PM   #4
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sub panel wiring


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Explaining this to an employee at Home Depot who I was told was a master electrician said this should work, though he had never seen a panel like that.
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Old 09-09-2011, 10:45 PM   #5
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sub panel wiring


I installed much the same in my detached workshop a couple years ago. A 12 space GE 100a panel, backfed main breaker with hold-down, #6 for H-H-N with #10 Ground, 60a in the main panel, etc. Works great.
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Old 09-10-2011, 09:37 AM   #6
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Thanks all for your replies. It was good to hear that the 100amp breaker will energize the rest of the bus bars below. Neither of the non-hot bus's appear to contact the metal of the panel itself (I know the neutral one shouldn't be) though and the one I'm using for grounding has no where to screw in a bonding screw, so how should I ground that bar to the panel?
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Old 09-10-2011, 10:05 AM   #7
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Thanks all for your replies. It was good to hear that the 100amp breaker will energize the rest of the bus bars below. Neither of the non-hot bus's appear to contact the metal of the panel itself (I know the neutral one shouldn't be) though and the one I'm using for grounding has no where to screw in a bonding screw, so how should I ground that bar to the panel?
Don't forget, the back fed breaker needs a hold down.
Does the other bar have a place for a bonding screw? If so, use that for the ground bar and the other for the neutral. If there is no place for a bonding screw is there a bonding strap somewhere in the panel?
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Old 09-10-2011, 10:32 AM   #8
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There is a bonding strap which I removed since you arent supposed to join neutral and ground in a sub panel. I need to check to see if there is a hole there for the bonding screw and maybe only hook the bonding strap up to the ground bus then screw the bonding screw into the bonding bar so it touches the panel (and not the neutral bus)?

Not sure what you mean by a hold down for the back fed breaker? The back fed breaker being the 100amp breaker in the sub-panel? And whats a hold-down?
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Old 09-10-2011, 12:18 PM   #9
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There is a bonding strap which I removed since you arent supposed to join neutral and ground in a sub panel. I need to check to see if there is a hole there for the bonding screw and maybe only hook the bonding strap up to the ground bus then screw the bonding screw into the bonding bar so it touches the panel (and not the neutral bus)?

Not sure what you mean by a hold down for the back fed breaker? The back fed breaker being the 100amp breaker in the sub-panel? And whats a hold-down?
The bonding screw will not be used. You defeat all your purpose regarding separation of neutral and ground by installing the screw in the sub panel.
Don't use it.

They make a kit to hold the breaker down. It's only because it's a main breaker. It will work without it, but you should use one.
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Old 09-10-2011, 12:21 PM   #10
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When a main lug panel has a breaker snapped onto the bus and it is a back fed the main disconnect, that breaker has to have a hold down bracket so it doesn't accidentally get knocked off the bus. Panel manufactures have these kit available.
Back fed means you are connecting live power to screws so it is "backward" from a normal breaker that is snapped onto a live bus and the output is the screws.
Can't you use the other bar for the neutral and the bar with the bonding strap as the ground bar?
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Old 09-10-2011, 12:23 PM   #11
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The bonding screw will not be used. You defeat all your purpose regarding separation of neutral and ground by installing the screw in the sub panel.
Don't use it.
JV. He has two bars that are both isolated. Should he buy another bar and mount it to the panel case as the ground?
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Old 09-10-2011, 12:23 PM   #12
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If you post a pic of the panel someone can tell if the backfeed clip is needed.
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Old 09-10-2011, 12:28 PM   #13
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My exact question a7ecorsair! Counldn't have said it better myself. I'm hoping to avoid having to buy and mount another ground bus and just run wire from the one isolated bus that I'm using as ground and attach it the panel tucked under one of the screws that mounts the panel to the wall. Is this kosher?

Thanks to you guys and doing more internet research I now understand the hold-down and back-feeding issue. The grounding issue is what I want to iron out.
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Old 09-10-2011, 12:36 PM   #14
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Unfortunately the picture I took earlier is to big in file size and I cant attach it. I'm convinced I do need a hold-down though for the 100 amp breaker in the sub-panel to do it right.
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Old 09-10-2011, 12:36 PM   #15
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The ground wire from the feeder will attach to a ground buss. You cannot just connect it to a screw that is holding the panel in the wall. you will also need the ground buss for the ground wires from the circuits.

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