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Old 08-22-2009, 04:47 PM   #1
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Proper cable entry into breaker panel


I picked up a new combo panel MBE2040B200BTF, which is a semi-flush side-by-side panel with a single breaker row that still fit standard studs. All of my 6 or 7 load cables will enter the top of the panel, but there are only 4 small punchouts and one large 2.5" punchout on the top of the breaker side of the box. Due to the narrow dimensions, there is no room to add more punchouts.

I would guess from looking at the old panel that one or two 12-3 cables could easily share one of the smaller punchouts and use a single metal cable clamp. The larger 10-3 cables would probably only fit one per hole. What is the proper way to use the larger punchout if I need to? Do I need to use a hub? If so, can the cables simply be zip tied together in a bundle or do I need to clamp them in some way?

I can already tell that trying to wire this box with all 20 positions would be a real challenge. I'd have to add another neutral bar so I may do that up front even though I won't use more than 14 positions right now. Would I be smarter to start wiring from the top of the breaker row or the bottom?

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Old 08-23-2009, 12:00 PM   #2
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Proper cable entry into breaker panel


Is this the panel you have? The specs say it is a flush mount panel not semi flush. If you mount it flush, all the KO's will be inside the wall. In this case you can make all the holes (KO's) you want in the top.
If this is not flush and extends out from the wall you should not use the top to enter. If your service cable or conduit comes in from the top you will need a hub or other product designed to keep water out.
I would not use the top if I could do it another way. Like the branch circuits out the back and service in the bottom. Where is the service cable or conduit? The top or bottom?

Yes, you can put more than one cable in the connector if it says so on the package.


Last edited by J. V.; 10-09-2009 at 01:19 PM.
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Old 08-23-2009, 12:50 PM   #3
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Proper cable entry into breaker panel


Sorry I didn't mention that my service conduit is now underground and enters up thru the sill plate. That is why I am replacing the panel.

Yes, the pic above is the panel. It comes with the mounting flange shown, with 3.5" of the box in back of the flange and 2" in front of the flange (5.5" overall). You could remove the flange and mount it differently, but I plan on using it as is since it fits well in my 2x4 stud space. Since my siding is 1" thick the box is going to stick out 1", so I call it a semi-flush mount. Someone with thicker siding may call it a flush mount. The Siemans panels seem to be better built, but they are 7" thick and would stick out alot more.

The load cables all have to enter the top of the right hand breaker compartment. They already come in from the top on my old panel so it makes no sense to do it any different. On the new panel this is a 7" by 3.5" square area with the punchouts described above. There is certainly enough area to bring in all the cables I could possibly want as long as I use the large punchout for some of them. What would be the proper way?

I believe there at least needs to be somthing to protect the cables from the jagged edge of the hole, and a simple threaded plastic fitting would do that. Do they need to be clamped too, if so how?
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Old 08-23-2009, 06:42 PM   #4
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Proper cable entry into breaker panel


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Originally Posted by tns1 View Post

I believe there at least needs to be somthing to protect the cables from the jagged edge of the hole, and a simple threaded plastic fitting would do that. Do they need to be clamped too, if so how?
Yes, they need to be both protected and clamped.

http://www.arlcatalog.com/NM%20Cable...Connectors.htm


http://www.arlcatalog.com/NM%20Cable...Connectors.htm

http://www.arlcatalog.com/NM%20Cable...Connectors.htm

That's what connectors are for.
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Old 08-23-2009, 09:24 PM   #5
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Proper cable entry into breaker panel


Looking thru the NEC, I see a bushing requirement where conduit or cable enter a box, but I don't see any clamping requirement other than "within 12" from exit from a raceway, etc."

All my load cables come down thru a hole in the header a few feet above my panel. It would be very easy for me to use a short length of 2" pvc conduit with a threaded coupling to mate to that large knockout on the panel. The open end of the conduit would be within 12" of where all the cables are stapled to the framing. Most of the cables would fit this one conduit. This would seem to satisfy all the requirements. Does it?
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Old 08-24-2009, 02:31 PM   #6
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Proper cable entry into breaker panel


Another thing. Since this panel is taller than the old one (and single row vs double row), The existing cables are probably not long enough to reach some or all of the breakers. There is no slop in the cables. Do I need to add a junction box above my panel to extend the cables? Do I have to wirenut or do they make terminal strips that could go in the box instead?
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Old 08-24-2009, 02:44 PM   #7
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Proper cable entry into breaker panel


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Since this panel is taller than the old one (and single row vs double row), The existing cables are probably not long enough to reach some or all of the breakers.
If the cables come from the top and the new panel is taller, this should help with cable length.

In my area we are allowed to run the cables into the panel without clamps..... just bushings of some kind.


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Would I be smarter to start wiring from the top of the breaker row or the bottom?
Terminate your longest cable at the bottom and leave room at the top for the shorter ones.
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Old 08-24-2009, 07:29 PM   #8
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Proper cable entry into breaker panel


Once the new panel is in place, the bottom breaker would be 8" lower than lower edge of the old panel. The old wiring did wrap around the breakers some, so I see that most will still reach, but 2 or 3 #10 neutral wires and some ground wires were clipped short and will need to be extended.

Are wire nuts inside the panel OK, or is there a better way?
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Old 08-24-2009, 07:44 PM   #9
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Proper cable entry into breaker panel


Wire nuts inside the panel are ok. You can tie the grounds together, but the neutrals need to seperate.
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Old 08-25-2009, 08:01 PM   #10
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Proper cable entry into breaker panel


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You can tie the grounds together, but the neutrals need to seperate.
This is his service. They are all tied together.


I hate to muck up a new panel but sometimes wirenuts are the only way to go.

You could bump the panel up a few inches and have the POCO lengthen their wires ????
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Old 08-26-2009, 07:16 PM   #11
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Proper cable entry into breaker panel


The service wires are not an issue since the underground has not been pulled yet. The panel would have to be a foot or more higher than normal to do it without extending the wires. I just thought there might be something better than wirenuts, like some kind of inline crimp or soldered connector that could be covered with shrink tubing.
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Old 08-26-2009, 07:41 PM   #12
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Proper cable entry into breaker panel


Quote:
Originally Posted by tns1 View Post
I would guess from looking at the old panel that one or two 12-3 cables could easily share one of the smaller punchouts and use a single metal cable clamp. The larger 10-3 cables would probably only fit one per hole. What is the proper way to use the larger punchout if I need to? Do I need to use a hub? If so, can the cables simply be zip tied together in a bundle or do I need to clamp them in some way?
Do yourself a favor & don't use the plastic connecters, Royal PIA
I've seen cable clamps rated for (2) 12-2's
Larger wires I have always seen 1 per knockout
I've never seen a larger knockout used for multiple cables ??
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Old 08-26-2009, 11:25 PM   #13
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Proper cable entry into breaker panel


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I've seen cable clamps rated for (2) 12-2's
Larger wires I have always seen 1 per knockout
I've never seen a larger knockout used for multiple cables ??
I saw those clamps also. I think they were for a 1.25" or 1.5" punchout. That does not buy me enough. I have 7 cables right now and want some extra for later. I need at least 4 cables in that hole. I could either buy a punchout tool and put in a pattern of smaller holes on top of the existing large punchout but it would probably just fall out anyway.

I could put a horiz member just above the box to staple to but the cables are going to be naturally bunched together there. Since the total run from breaker connection to 1st staple is only 4ft right now, why not use the large punchout for what it was designed to do and attach a short length of conduit as I described. AFAIK there is no requirement to fix or clamp cables inside a conduit, only after it leaves the conduit.

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