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A couple more sub panel questions

Posted by BradleySmall (My Page) on
Tue, Jun 14, 11 at 22:23

This is a sanity check, just to make sure I am not being led astray. I am wiring a 100 amp sub panel, and using #2 aluminum from my main panel.

So I have 2 wires attached to the breaker. Do I have to Anox them?

The other two wires need to be ground and neutral, but in the panel those are combined so they have merely to be lugged into something ground in the panel. That could be either bar, or and here is where the question comes in, the panel box itself. (so says the inspector)

I went to the electrical supply and they sold me something that looked like this:

http://lugsdirect.com/images/2S2.JPG

I Anoxed the back of it, drilled and tapped a hole in the panel box and screwed the heck out of it. I then Anoxed the wires put them in it and screwed them down as tight as my little hands could.

Is this actually a correct solution? Do I also need to use a torque wrench to set these things to some particular ft/lbs or something?

For the other panel, since it has a breaker to connect two wires to, and a lug to connect into one bar that is isolated from the ground then the other large wire coming in will also be lugged directly to the panel box with something that looks like this:

http://lugsdirect.com/images/S6-slotted-500x.jpg

I have not done that part yet, since I ran out of daylight tonight. I just want to make sure I am not doing something stupid or dangerous. It just sounds funny, in that 'too easy' sort of way.


Follow-Up Postings:

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RE: A couple more sub panel questions

For a sub-panel you remove the bonding screw from the neutral bar to the panel box itself.
This isolates the neutral bar.
Another bar can then be installed for the grounding bar.
This bar IS bonded to the panel box.
Most panels come with screw holes located to match the manufactures secondary bar (and the bars often some with mounting screws.
In many cases the bonding screw comes with a small tab to attach to the bar.
You can simply re-use this screw and tab to ground the new grounding bar.

All neutrals must be landed on the neutral bar, all grounds landed on the grounding bar in a sub-panel

The incoming feed neutral lands on their respective bars.

"Is this actually a correct solution? Do I also need to use a torque wrench to set these things to some particular ft/lbs or something?

Where are you planning on landing the branch circuit grounds?
The added bar will already have a larger connection for the ground from the feed, and provide a place for all the branch circuit grounds.
It is not incorrect as long as you also have a ground bar that is tied to the panel box, just a lot more work than was needed.

All stranded aluminum cable requires anti-oxidant on every connections.
The strands need to be separated, cleaned (you are trying to remove the aluminum oxide), treated with some form of anti-oxidant coating, then placed in the termination (if under a screw they need to be twisted back together).

A torque wrench for tightening screws has been required for multiple code revs now.
The torque required should be listed on the nameplate of the panel board, or on the packaging for secondary bars.


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RE: A couple more sub panel questions

The branch circuits will be using the two bars. My only concern was for the big grounding wire coming from the main panel. On my subpanel, I have a lug on the neutral bar so I will connect one of them to that. The other one is to be connected to the 'mechanical' lug that I showed the picture of. I plan on simply screwing it to the panel box itself.

So if I installed a non-isolated bar or a mechanical lug it essentially is just bonded to the panel, which ultimately is bonded to the non isolated ground bar. Am I thinking correctly?

Do I need to be concerned to remove paint or anything, or is the screw contact through the steel enough or does the paint not matter as far as contact goes?

Just to be sure, where the aluminum goes into the 'breaker' I need to put the Anox there as well? That was the only place I haven't put it where I made connections. I wasn't sure that anything was supposed to go on any part of the breaker.


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RE: A couple more sub panel questions

I'm having a hard time with your terminology and understanding what you are trying to do. The ISOLATED neutral bar has to be used for the neutral feeder from the main panel as well as all branch circuit neutrals. This isn't a ground it's the grounded current carrying conductor. It can not be electrically connected to the case or any of the equipment grounds PERIOD.

If there are existing mounting holes pre-tapped, you don't need to further prep the case to install ground bars.


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RE: A couple more sub panel questions

Ok, we are in agreement. I must be saying it wrong. On the sub panel, it is a Cuttler Hammer and has a screw and pin that you remove to isolate the neutral from the ground. The neutral is no longer connected to the panel box itself.

On the neutral bar there is a lug connector. On the ground bar, there is not.

From my main panel, I have 4 wires of #2 aluminum coming into this sub-panel. The two hot wires will be connected to the 100 AMP breaker that feeds the two hot bars down the center of the panel. Next, one of the other wires will connect to the isolated neutral bar via the lug that accepts this huge wire. I now have an extra wire that needs to go to ground. That 'mechanical lug' that I posted a picture of above is what I am to connect it to, and it subsequently will be connected directly to the back of the panel box as though it were a ground bar with 1 connection.

That thing 'mechanical lug' when I connect it to the panel, does it need any special preparation to make a better connection other than to be screwed to it; such as removing the paint from the metal where it is to be attached, or some thing else that I haven't thought of?

On the main panel, I have the 4 wires that will be going to the sub-panel, and 2 of them will go into the 100 amp breaker there. The other two need to go to neutral/ground (in this case they are the same right?) So I used the other item I posted which simply has a hole to connect and 2 holes with screws to hold the two wires. This is connected directly to the metal panel box, which presumably should connect it to both ground and neutral since neither is isolated in the main panel.

I hope I am coming close to a reasonable explanation of what is going on. Sorry if I blew the vernacular, I will try harder to call things by their proper names. :)

I guess, ultimately, I want to treat these things (mechanical lugs) as though they were additional ground bars.


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RE: A couple more sub panel questions

"On the ground bar, there is not."

Sounds like the wrong ground bar.

There are also adapters made that have a larger lug and occupy two adjacent positions on a bar.

How are you landing both the neutral and ground in the main panel to feed the sub?
They will come of the same bar. and an adapter is also often needed there for each line.

Even the bars have a maximum wire size that can be used in the hole provided.


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RE: A couple more sub panel questions

Hello BradleySmall:

You will need a grounding Bar like the one that is in the drawing. Every new Circuit you wire NEEDS a Ground wire to go to this bar.. You can't put all your new Circuits in the one big hole that you now have.

Photobucket

Hope this helps

Let us know how you made out with your wiring project

Have A Nice Day
Linesman


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RE: A couple more sub panel questions

What I have for the sub panel is a Cutler Hammer 100 amp Main Breaker

http://www.lowes.com/ProductDisplay?partNumber=242400-82364-BR2040B100V9&langId=-1&storeId=10151&productId=3027588&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

It has a ground bar and a neutral bar. They are connected but can be disconnected by removing a screw and removing a piece of metal. When you do that, the neutral bar is then isolated. There are no power lugs on these, but instead there is a 100 amp breaker in the first position and you simply run your hot lines into that and it supplies the two hot 'bars' that all the breakers connect to.

On the neutral bar is a 'lug' attached to the top that has an opening in it capable of connecting #2 aluminum, and below that there are a bunch of holes with screws for attaching each of the neutral runs from my romex to my outlets. On the other side is the ground bar. It does not have a lug like the neutral one, just holes and screws to hold the ground wires from the circuits.

They sold me something that looks like the attached image
which I want to attach to the metal of the panel box.

I am sorry I am explaining this so badly.

Here is a link that might be useful: lug


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RE: A couple more sub panel questions

You want one of the ground bar kits with that ends in "20"
like the GBK520 or GBK1020. This will have the extra #6-2/0
terminal on it.

Why anybody would use a type BR panel in a new installation is beyond me.


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RE: A couple more sub panel questions

So I shot the photos tonight. I appologise for the cell phone image, but that is what I had with me at the time. They are in photobucket as an album, along with a woodpecker that decided to visit the other morning. I commented each photo in the description and use the wonderful drawing technology they offer to try and circle the critical areas of which I spoke.

Here is a link that might be useful: Here are the photos with comments


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I gotta take the bait

ronnatalie --

That is a baiting statement if I ever heard one... :)

If you care to explain what you mean by it, I will be happy to share my specific personal reasons for choosing this particular panel.


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RE: A couple more sub panel questions

1. You are supplying this sub-panel from a 100A breaker in your main panel, but #2 aluminum is only good for 90A feeders.

2. You don't need a #2 alum ground wire. For 100A feeders you would only use a #6 alum ground, which should fit in a ground bar.


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RE: A couple more sub panel questions

According to the inspector I can use either #2 Aluminum or #4 Copper. That would be required for the two hot and 1 neutral runs. The ground can be #6 Aluminum or #8 Copper.
(You are the first person to tell me #2 Al is not appropriate for 100 AMP.)

The reason I am doing all 4 in the #2 Aluminum is because I can :) I had a friend that sold me all the wire at a rate lower than I would have spent on the #4 aluminum or #8 copper itself. The inspector said he didn't mind if I used bigger wire than necessary, but not smaller.


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RE: A couple more sub panel questions

It would probably be less confusing if you did not refer to Neutral and Ground as the same thing. They aren't, even though they are tied together at the main panel.

Grounds are usually smaller than Neutrals and Hots.

I think a good electrician will always put the Neutrals on the Neutral bar and the Grounds on the Ground bar, even if they are tied together (a Main panel). This gives a cleaner appearance and keeps you out of trouble with a subpanel.


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RE: A couple more sub panel questions

Separating the grounds and neutrals in the main has no advantage either from a "cleaner appearance" or any other practical purpose. Besides, how are you going to do that in panels that don't give you two terminal bars?


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RE: A couple more sub panel questions

weedmeister -
If they are connected together, then in my mind they are the same thing. But I accept the criticism. As for what a good electrician will or will not do, I can only assume that the primary attack involves safety. The aesthetics are soemthing else. Granted, a clean well arranged box will be easier to work on and maintain, but I doubt that any electrician would look at somethng which is bonded directly to the box and question whether or not it is connected to neutral and or ground if he knows the box.

There are main panels, that do not have 2 bars, but only 1 which is both neutral and ground. I can't imagine a working electrician putting in a separate bar, and bonding it, just to say it is there and make things 'appear cleaner.' That is, however just my opinion. I am not an electrician.

Before they accepted the new code in March, I would have only needed carry 3 wires from the main panel anyway. I am not certain that second wire will gain me much, but it will cause me to pass my inspection. :)In addition to all that, there will be a ground bar and copper from that to the sub panel will provide whatever other protections it can. As well, #2 buriable jacketed aluminum is some seriously stiff stuff. It is thick and unweildly and dragging it all around the stupid main panel unnecessarily seems more like an exercise in discipline and self flagelation than practicality. As it is, the large breaker as well as the lug points are as close to the conduit as possible. Such a circuit will be quite obvious and easy to trace to even the most casual observer. I think that adds to maintainability and safety too.

I am not sure my solution looks that much less 'clean' appearance. The fact that the stupid main panel is damn near a rats nest took care of that. If I feel froggy one day I will try and clean it up, but there is something to be said for 'if it ain't broke don't kcuf with it' and I have more interesting things to do with my time. :)

And, in my opinion, if the inspector likes it and signs it off, then it is prettier than speckled pup in a little red wagon! :)


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RE: A couple more sub panel questions

If they are connected together, then in my mind they are the same thing.
They are not the same thing, they are only connected at the service entrance. The grounded conductor (i.e., the neutral) has current flowing on it in normal operation. The equipment ground does not. Because of resistance of the currents flowing, that neutral in the subpanel can be at a different potential than the house ground. You want an "express" path for fault current (things that are flowing on the ground but shouldn't).

What "new code" in March? What bizarre location is this. Running separate grounds and neutrals beyond the service disconnect has been the code in the over 25 years I've been in the industry. What has changed in the past five or so years (depending on local adoption) is that if you had feeder to a different structure with it's own ground system that didn't have any other metallic connections to it, could omit having a fourth wire in the feed.


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RE: A couple more sub panel questions

"What "new code" in March?"

I do not know where the OP is, but Virginia is very slow at adopting code updates, and sometimes even skips a revision.

Many AHJs are run behind, especially if the code is adopted at the state level.

Before the Virginia Uniform Statewide Building Code (USBC) was adopted we had counties all over the map with changes.
A number of them applied the 180 V-A limit to residential wiring for sizing circuits.
At least that junk went away.
Sub-municipalities are NOT allowed to make any local changes to the USBC.
The AHJs sometimes still have varying 'interpretations' but seem to back off when you ask them to cite the section they are alleging is in violation.


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RE: A couple more sub panel questions

Prior to March 1 they allowed you to run 3 wires (NEC2005 I think) from the main panel to the sub panel 2 hot and 1 neutral. I guess in such case the neutral went to the isolated lug and the only thing to the ground was the ground rod. Though I am not certain of that.

Now they want (NEC2008 I think) 4 wires from the main to the sub. 2 hot and 1 each neutral and ground.(apparently I can no longer eliminate the 4th wire in the feed) (plus a local ground rod) I understand the difference between neutral and ground, but what I am saying is in the main panel they are physically connected and intermingled and essentially treated no different one from the other since the bars are connected by bonding strap. If I connect a wire to the ground bar, or the neutral bar, or the panel box itself it is bonded both to neutral as well as ground with no differentiaton, separation or isolation.

When it gets to the sub, the neutral is isolated, but both wires coming into the box from the main panel are connected at the main panel. The isolation in the sub panel will apply to branch circuits and the ground bar will only have bare copper and/or possibly coded green wires connected to it, and the neutral will have only white or coded white wires. The isolation at the panel makes sense to me, but would make just as much sense if it only had the ground rod connection and simply three wires from the main panel. I am sure someone can explain the logic behind the second neutral/ground wire coming from the main panel to the sub, but I just assume the local ground rod connection clears up any other issues there. I am also not sure why they don't care for me to run a second ground rod 6 feet away either.

As for asking AHJ to cite chapter and verse, I am not inclined to piss the guy off who can approve me or stick me in paperwork hell. Whatever he wants he gets :) Kind of the same attitude as not argue with cops, they have guns and sticks and pepper spray and nasty taser thingies... Sometimes it is best to just says "yes sir" and move on with your life.

So far my inspector has be more than helpful, patient and just plain nice. He has answered every stupid question I posed to him, and suggested all sorts of things that made this job smoother. I am doing this 1 or 2 hours at a time, and to the best of my research and abilities I am doing it safe, sane and consentually.... oops skip that last one, different topic all together. :)

If all goes well, I will have both my son and my daughter's BF interested in impressing me for father's day weekend, perhaps I should invest in a second shovel, and I can have a trench done before the weekend is out :D


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RE: A couple more sub panel questions

"Prior to March 1 they allowed you to run 3 wires (NEC2005 I think) from the main panel to the sub panel 2 hot and 1 neutral."

Not under the NEC for a sub-pane in the same structure.

4-wires have been required for a sub-panel in the same structure for a very long time.

The old exception was for using 3-wires to feed a separate building's sub-panel if there was NO other metallic connection between the buildings (phone, plumbing, LAN, cable TV, etc.)


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RE: A couple more sub panel questions

Sorry, I should have clarified, this is a sub panel in a detached shed, with no other metallic connections to the main structure.


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RE: A couple more sub panel questions

"this is a sub panel in a detached shed"

Pretty important.


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RE: A couple more sub panel questions

In my own meager defence, I was referring to the panel show in the photo where there exists two bars and they are on opposite sides of the box. As for that 'good electrician' thing, I asked an electrician my company hired to do some work why he did this. He indicated that was how all the guys at his company were trained to install circuits in a panel, grounds on one side, neutrals on the other.


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RE: A couple more sub panel questions

And what happens if he works on something other than the type BR panel. There are other panels where the "neutral" bar when the jumper is removed is just another bar next to the ground bar. On some panels, there is no separate bar until you install it when necessary. Frankly, I find it neater if the ground and neutral are landed adjacent to the same spot on panels which don't requie separation.


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RE: A couple more sub panel questions

So far so good. I have learned that ground rods are harder than I initially thought, and more difficult to drive. I got the first 4' in within about 5 minutes. After that, I could no longer pull it out of the ground, and had to go to beating it in. I have a 3lb drilling hammer, and initially I was concerned with harming the rod, so I was trying to pad it with wood as I beat it. I don't recommend this :)

I put the clamp on the thing, and commenced to wetting the ground and beating on the rod. I have another 8" left but now I have to dig my trench to bury the other wires.

I have a hammer drill, but for the life of me could not figure how to employ that without some special bit (which I didn't have).

Anyway, back to trenching which I am not looking forward to, after which I get to run wires through the studs and stuff.

My ceiling is less than 8' high, any good recommendations for lighting? Looking for the most bang for the buck, easiest maintenance, and longest life. You know, I want everything for nothing :) I am considering fluorescent or LED but haven't decided which. If I go with LED I will put cans in, but if fluorescent I will only put up outlet boxes. Unless there is something else out there to consider?


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RE: A couple more sub panel questions

There's a specialized bit for hammer drills. Costs about $40.
They also make them for pneumatic hammers. You might check your local rental places to see what they have.


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RE: A couple more sub panel questions

I would, except, this is probably the last ground rod I will ever drive. :)


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RE: A couple more sub panel questions

Okay!! The rod is driven! I borrowed my neighbor's 4# engineers hammer. BTW, a 4# hammer with full swing, slamming into a 6" deep puddle of mud, can cover your whole face and most of your shirt in one stroke :D

Time to start digging, and cementing the conduit.


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RE: A couple more sub panel questions

My ground rods took five minutes each, no kidding. I guess the soil is still soft, in Oregon in June. I didn't need the 6 lb maul until the last two feet, and then it was just tap-tap. I did dig a small hole and run water into it as I worked the rod up and down. Digging the shallow trench to bury the ground wire will take longer.

Sounds like you and I are doing similar projects. I should finish this weekend, enough to call for inspection. My garage is only 5 feet from the house, so I had it easy.


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