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sub panel wiring

4K views 25 replies 8 participants last post by  Jim Port 
#1 ·
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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#3 ·
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.
 
#6 ·
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?
 
#8 ·
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?
 
#9 ·
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.
 
#10 ·
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?
 
#13 ·
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.
 
#15 ·
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.
 
#17 ·
JIm,

I'm probably not being clear enough on this:

My thought is to attach the ground wire from the feeder to one of the two neutral bus's (not to the panel), the one which has all the ground wires attached to it already from the smaller wires feeding the various outlets in the shed (the bus serving as neutral has the white neutral wires already attached to it, and the feeder neutral I will attach to this bus). To this neutral bus that I plan on using as the ground bus, I will also attach the wire that goes to the grounding rod outside. My main question is since this bus I'm using as ground does not contact the metal panel box in any way, would simply running a wire from this bus to a screw that mounts the panel suffice in grounding it, sort of serving as a grounding screw?
 
#19 ·
If this panel is listed as suitable for service equipment and came with a bonding screw, it will have a place to put it so it can screw into the panel and bond one of the grnd/neutral bars, usually near the top or bottom of the bar. Hopefully it will be under the right hand bar. Remove the set screws on the right hand bar and look for its position. May even be under a screw you have a ground wire on now. If it is, move the wire to a different set-screw.

No, using the screw that mounts the panel is not acceptable. You could bolt on a lug to the side or back of the panel though.
 
#22 ·
As hard as it is to believe, I for the life of me cant find where this bonding screw goes. I like your idea SD515 of bolting a lug to the side and attaching to that. I will look one last time under some of those existing set screws to see if it can go there but I'm pretty sure it wont (those set screws are bigger diameter then the bonding screw). Thanks everyone for all your help.
 
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