New panel & wiring trough

Old 12-05-04, 09:16 PM
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New panel & wiring trough

I've want to install a new 40-position main breaker panel to replace my old 12-position panel. The new panel will be on an wall adjacent to the old panel.
The old BX feeds will not reach over to the new panel.
I've already mounted a 36" x 6" x 6" wire trough in the rafters above the new panel in a place where the old BX can easily connect. My goal is to have all of my old and new (romex) wiring spliced in the trough. I want a neat professional looking installation. I do not want to use the old panel as a splice box. I want to pull it out of service. I will use a licensed electrician to move the mains.
Here's my issue...
1. Will the Code allow me to splice 40 circuits in a trough this size?
In actuality I will not be using all 40 breakers, but I just how many circuits will this size trough allow? This assumes a mix of BX and Romex circuits --all 12 ga. I'm not sure how to calculate the fill size.
2. Next, I want to run EMT up to the wire trough from the new panel. Assuming 3-conductors for each of the 40 possible circuits, how many 12 ga wires can I use in 2" EMT?
3. How many 2" runs from the panel to the wiring trough do I need.
Any obervations/suggestions on this project will be greatly appreciated!
Old 12-06-04, 07:16 AM
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For 40 circuits, you would have 80 current carrying conductors, not 120. (grounds don't count for derating). After (I think the number is) have to derate. So if you can fit 8 conduits up, you should be OK.

Not sure what kind of "trough" you're talking about, but all splices like you're talkng about have to be made in junction boxes to be code. If the trough is for protection it COULD pass, but I can't say for sure.
Old 12-06-04, 07:43 AM
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You'll have to either use a whole bunch of junction boxes, or several larger ones.

Assuming you have only 12 circuits you'll have 24 current carrying conductors that you'll need to "transfer" over to the new panel. That will require probably 2 conduits, probably 1" for easy of pull. You can of course simply use NM-B if allowed, but the actual splice has to be done in a junction box. Accessible junction box.
Old 12-06-04, 08:39 AM
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I consider you'r plan to be very impractical. You state--- "MY goal is to have ALL (old & new) wiring spliced in the trough".

Point 1--- "If it's not there, it can't fail"; this applies to un-necessary wiring-connections in the Branch-Circuit conductors that could be avoided by "direct-connections" to the wiring terminals in the Service Panel.

Point 2- The number of conductors; Presuming you will connect 40 B-C's using 3-wire cables, 2 B-C's/per cable,you will have 20 X 3 = 60 conductors entering
the trough, and 60 conductors leaving the trough. In addition, the 20 N-M cables entering the the trough includes 20 Equiptment Grounding Conductors which must be extended to the Equipment Grounding connection-point in the panel for conducting Fault-Currents back to the source.

Point 3: De-rating the ampacity of conductors in race-ways with more than 3 conductors.


If you want a "neat, professional" installation, I suggest this; fasten 2 vertical 2X4 studs to the panel back-board on the Left/Right sides of the panel- screw a rectangular piece of 1/2 plywood to the 2 studs so that the plywood board extends X" below the bottom of the panel, X" above the top of the panel, and with a "cut-out" section of the board that exactly matches the dimensions of the panel.After the board in fastened to the studs, you (obviously) fasten the panel-cover on the panel. The result is a very neat "Flush-panel" appearance with the cables concealed behind the board.

Good Luck & Enjoy the Experience!!!!
Old 12-06-04, 08:42 AM
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Is this really the best way to proceed? Since you must have your utility company disconnect the main feed, why not just remove the old panel, and simply replace it with the new one in the same location? With only 12 old cables to move, this should be fairly straight forward. It would be a whole lot neater, avoiding all the conduit, splices and extra electrical boxes.

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