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Old 01-03-2014, 10:25 PM   #1
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Use panel as a junction box?


I am planning to repair an obsolete panel by replacing it with a new panel mounted in an adjacent stud bay. The main disconnect breaker (100A) is outside next to the meter. I am thinking to leave the old panel in place. I plan to pull out all the old breakers, hot buss bars, and buss mounting hardware to make more space available.

All the existing circuits come into this panel. It is in a narrow stud bay. I would like to use the old panel as a large junction box and pigtail circuits over to identically sized breakers in the new panel. The BLK and RED feeders (#2 AL) in rigid from the outside panel are long enough to be routed through the old panel and to be connected to the lugs in the new panel. The WHT neutral feeder (#2 AL) is not long enough to reach into the new panel without an extension. Also the GRN ground (#6 CU) from a water pipe will not reach into the new panel.

Can I use the old panel as a J-box?

Can I simply extend neutral and ground cables to unbonded neutral and ground bars in the new panel?

Are the neutral and ground bars in the old panel suitable for extensions to corresponding bars in the new panel?

Do I need to be concerned about having a high current feeder joint (for the neutral) in the same J-box with lower current pigtails (lights, outlets and HVAC)?

Thanks for your advice.

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Old 01-03-2014, 10:53 PM   #2
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Use panel as a junction box?


I would put the panel in the same bay and avoid another splice. Just rework or cut the stud bay to the proper width.

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Old 01-03-2014, 11:37 PM   #3
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Use panel as a junction box?


PS... I live in Los Angeles.

Jim, I have thought about this. In order to do what you suggest, I think I would have to open up the wall, disconnect everything (leaving me with no electricity), carefully cut the rigid conduit with the feeders in it, cut an off center knock-out hole to match the position of the rigid, put in a header and a new stud, drill holes in the header for NM cables coming down to the panel, then mount the new panel and connect, close up the wall, plaster the seams, then sand and paint to match the existing wall.

This seems like a lot more work, fiddling to get things to line up and look right, and a longer time without electricity (which I would need to do some of the work), than if I just cut a drywall opening the exact size I need for the new panel, drill knock-out holes I need for conductors coming from the old panel to the new panel through the stud, mount the new panel, pull individual conductors between the panels and wire things up.

Are there electrical, safety and code downsides to extending conductor paths between the panels?

Thanks for helping me think this through.
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Old 01-03-2014, 11:47 PM   #4
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Use panel as a junction box?


Yes. That is how it is done all of the time. It should only take an hour tops to connect Mains power back to the new panel. Now of course a real Sparky, will run a Genset for lights and utility power for tools, while Mains power is shut off during the panel install.

Once you get Mains power wired in from the meter, then you can go through and work on all of the branch circuits.

I would have the wiring checked by a Licensed Electrician with a Megohm, to check for any damaged wiring inside the conduit, before reattaching back to the panel.
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Old 01-04-2014, 06:37 AM   #5
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Use panel as a junction box?


How are you going to get the feeders from the old panel to the new panel? You can't just pop KO's in the sides of the panels and run the conductors thru the stud.
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Old 01-04-2014, 09:20 AM   #6
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Use panel as a junction box?


The old panel is acceptable for the branch circuits. I would run new mains supply direct to the new panel.
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Old 01-04-2014, 09:52 AM   #7
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Thanks, gregzoll.
I am reluctant to be working in or drilling into a live panel. I would run an extension cord over from a neighbor for that hour or so when I am without power. Good idea to check for feeder/conduit leakage, probably while feeders are not connected to the new panel.

I have periodically thought I would like to be able to check other wiring with specialized meters, one that would measure in the high megohn range, and another in the range of less than one ohm. Do you have suggestions for such meters? And yes, I will have a licensed electrician check my work.

k_buz,
I am planning to use a Square-D model HOM1224L125TC panel. It's cover is about the same size as the old panel cover -- for a good look. Homeline panels have a simple way to remove the guts of the panel. I think I would have enough room to drill holes straight through new panel side+stud+old panel side**. Then I would put in rigid nipples, tighten down nuts on both sides and add plastic bushings for smooth pass-through for conductors. One hole for feeders, large enough to accommodate a 1-1/4" nipple. 3 - 4 holes for circuits.

I think I will also add a bushing with a ground lug to the feeder conduit in the old panel and run a #6 CU to the new panel ground.

**If I need better control during the drilling process or space is tight, I would drill small pilot holes all the way through. Then pull the new panel out and individually drill through panel, wood and panel.

Would this pass muster?
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Old 01-04-2014, 09:57 AM   #8
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Use panel as a junction box?


Quote:
Originally Posted by LynnX View Post

k_buz,
I am planning to use a Square-D model HOM1224L125TC panel. It's cover is about the same size as the old panel cover -- for a good look. Homeline panels have a simple way to remove the guts of the panel. I think I would have enough room to drill holes straight through new panel side+stud+old panel side**. Then I would put in rigid nipples, tighten down nuts on both sides and add plastic bushings for smooth pass-through for conductors. One hole for feeders, large enough to accommodate a 1-1/4" nipple. 3 - 4 holes for circuits.
You think that is easier than removing the old panel and slapping up the new one?

With the panels installed, there will be no way to properly install a rigid nipple between the two panels. You need lock nuts inside and outside of the panel to secure it properly.
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Old 01-04-2014, 09:58 AM   #9
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Use panel as a junction box?


Quote:
Originally Posted by k_buz View Post
How are you going to get the feeders from the old panel to the new panel? You can't just pop KO's in the sides of the panels and run the conductors thru the stud.
I did something similar years ago. Get a 2.5 inch long pipe nipple large enough for your conductors. Remove knock outs (or drill holes) for the nipple, drill hole through stud. Slip the nipple into place and secure with lock nuts on both sides. Install insulated plastic bushings on both ends.
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Old 01-04-2014, 10:08 AM   #10
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Use panel as a junction box?


joed,
The feeder conduit comes up through the concrete slab. In order to route this conduit over about 16" to come up in the next stud bay, the bend left plus the bend back to vertical would lengthen it. Then the feeder neutral (at least) would not be long enough. So I would have to pull a new one. I would probably have to pull out all feeders and re-pull everything as a group.

I am hoping to keep this project more "short and sweet". But if it won't meet Code, I will have to reconsider.

How essential is this?
Thanks.
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Old 01-04-2014, 10:21 AM   #11
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Use panel as a junction box?


k_buz, njniles,
Yes, I was going to use 2-1/2" pipe nipples.

I would have lock nuts on the insides of both panels. Essentially I am compressing both panels against the stud. If I also have to have lock nuts on the outsides of both panels, then my "Plan A" will not work. Is this a code requirement?
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Old 01-04-2014, 10:27 AM   #12
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Use panel as a junction box?


Yes it is.
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Old 01-04-2014, 06:48 PM   #13
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Use panel as a junction box?


k_buz,
If I could come up with spacer nipples of the diameters I need (1-1/4" for the feeders) with length equal to the thickness of the stud, would that pass code?

Thanks
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Old 01-04-2014, 07:08 PM   #14
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Use panel as a junction box?


Lynn....what part of LA do you live in?

If you have the typical panel for the typical 50's house....yes, you can use it as a junction. But you might also want to think long term as well. If you have a detached garage....if your existing wire to it is overhead...you need to put underground in conduit.

I've been through the process twice on my house.

Have you already contacted SCE or DWP for a meter placement check? The inspector will not even look at anything until that is done.
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Old 01-04-2014, 10:28 PM   #15
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ddawg16,
I live in a development -- no detached garage. Power comes underground from a vault under the sidewalk. Service entrance box (meter and main disconnect breaker) are recessed in a stucco wall on the outside. What I want to replace is the main sub-panel inside. I don't think I will have to touch anything on the outside. So no meter spot.

Building & Safety's initial assessment of what I am doing is that I do not need to pull a permit. I plan to visit them in any case because I want to make sure what I am planning to do meets Code.

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