Isolating neutral bus from ground bus

I was looking at my sub panel beside my main panel. (It is about 2 feet away and was added a few years ago because of lack of space in
main panel).
I believe I read that the netral and ground busses must be isolated on a sub panel. When I checked with a continity tester, it beeped meaning they are connected. This is a Square D Homeline series model number HOMC2OU100C with a main breaker.
It looks like the bonding screw was removed though? There are two blue screws one at the neutral lug area and one at the ground lug area. I removed one and still contnuity. I removed both and no continuity. These look like the screws you remove to remove the interrior of the cabinet.
SHould I leave the screws out? Can anyone help me with this model?
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stryped wrote:

This panel is wired up, right?
If so, the neutral and groud buses must be isolated in this sub-panel. But each is connected to its respective bus in the the service entrance panel. Here, the neutral and the ground buses must be bonded. So that's what you are reading with your continuity tester.
Leave the sub-panel as you found it.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Your panels are too close to trust the ohmeter or whatever you are using to chec for discontinuity. And with many wires in the subpanel already in use I would not trust your testing. So disconnect everything and verify there is no connection between the neutral and ground buss.
Bob AZ
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The power feed from the main panel to the sub panel has been removed.
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And that has what, exactly, to do with the neutrals?
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On Dec 3, 8:56am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I am saying I have 4-3 Romaex, the whole thing was removed. (Including the neutrals).
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Then what's your question?
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On Dec 3, 10:40am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

If all main wires are removed (2 hots neutral, ground) and the green bonding screw is removed, why am I getting continuity between the neutral bus and ground bus?
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Because you messed up somewhere. Without seeing it first-hand, it's hard to say just where you messed up, but here are a few things to check:
- Have you confused the neutral and ground busses?
- Is there a jumper connecting the two busses?
- Is there a second bonding screw? I seem to recall from earlier discussions that your panel has two neutral busses. If they're bonded together, and to the box, and you removed only one bonding screw, well...
- Have you connected neutral and ground somewhere in your branch circuit wiring? Remove *all* wires (the branch circuit neutrals) from the neutral bus, and check again to see if there's continuity to the ground bus. If not, put them back one at a time until there is continuity -- then you've found a circuit with a problem. Don't assume that's the only such circuit.
- One way in which you can make an inadvertent connection between ground and neutral is to overtighten the cable clamp on a Romex cable enough that it cuts through the conductor insulation.
- Another way is through careless placement of ground wires in a receptacle box (touching the neutral screws on the receptacle).
- Yet another way is by failing to understand that ground and neutral are different things, and thus failing to understand that they need to be kept separate when making fixture connections.
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On Dec 3, 11:16am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

My detached garage has the two grounding busses. (The one this sub panel will feed.).
There are only two items hooked to this sub panel and they dont have a neutral. One to a 50 amp breaker for my upstairs 1 ton unit and one 20 amp breaker to my outside unit. (This is my small heat pump for a bonus room), Black wire to breaker, white wire to breaker, and ground. That is it.
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Post another photo. My recollection from the previous discussion a couple months back is that the photo you posted then showed two _neutral_ busses and one grounding bus, and you were confused about which was which -- you thought one of the neutral busses was the grounding bus, and you had no idea what the actual grounding bus was for.
I think you're still confused.

OK, so it's not a problem in your branch circuit wiring. What about all the *other* things I told you to check? (reproduced below)

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On Dec 3, 1:09pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

The photo you are refering to was to a second sub panel in the detached garage. This one is in my attached garage.
I think I have figured out what is wrong.
I dont think the square d panel I am refering to in the attached garage came with a grounding bus. (The GE panel int he attached garage did). What I was thinking was the grounding bus is actually I believe a second neutral bus.
I will check for continuity between the two busses in the cabinet and the enclosure and if there is none, will buy one or two grounding buses. I think that might be the problem all along.
What I dont understand is why the need to separate the neutral bus and ground as they all end up combined in the main panel anyway.
Also, I always heard it was bad to have multiple ground paths. If I have a ground rod for the house and one for the detached garage, arent these all connected? All sub panels will be attached to the house ground and the sub panel in the detached garage will also be attached to another ground rod. AM I misisng something?
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: :What I dont understand is why the need to separate the neutral bus and :ground as they all end up combined in the main panel anyway.
The problem is that if the neutral connection breaks there is nothing to indicate that there is a fault. The ground wire is carrying the current. The fault can go undetected indefinitely. Now, if the ground wire should break too, all of the supposedly grounded equipment downstream of the break has AC line voltage on its "grounded" frame -- a lethal hazard.
It is never permitted to have the ground conductor carrying any non-fault current, and that includes current shared with another, parallel conductor.
--
Bob Nichols AT comcast.net I am "RNichols42"

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Because the neutral conductor _carries_current_. If you combine neutral and ground anywhere except in the main panel, then all of your ground conductors *everywhere* are carrying current also.

Yes, you're missing a basic understanding of residential electrical wiring -- which is why a number of people have told you to hire an electrician.
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wrote:

Not everywhere, because there should be no cause for current to flow on equipment grounding conductors connected to equipment in good condition. Specifically on the feeder to the subpanel. The grounding conductor would be paralleled with the grounded conductor (sharing the neutral load), and could be an unsafe situation particularly if the grounding conductor is metallic conduit, and especially if the neutral is impaired by poor connections, etc..
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