Main panel upgrade - a few questions

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Old 08-05-20, 07:39 PM
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Main panel upgrade - a few questions

I'm upgrading my old panel to a new panel with many more spaces (same 100A service) and had a few questions.

1. Is this breaker considered a 2 pole 40A, as opposed to a 2 pole 20A (sometimes these two pole breakers will list amp capacity on each pole)? So it will cut off in the neighborhood of 40A on either phase?


2. I'll be running lots of 12/2 romex and older nm cable of same gauge or smaller. The Square D panel I'm moving to has lots of 1/2" knockouts on top, which is where most of the cables will enter from. Using 3/8" NM wire clamps that fit 1/2" knockouts, can I run 2 x 12/2 cables through a 1/2" KO? And 12/3 or a larger gauge requires either its own 1/2" KO or a larger KO depending on size, correct?

3. The new panel's breaker slots are a fair bit lower than the panel being replaced. Some of the cables are too short. Is it ok to pigtail using wire nuts INSIDE the main panel? It's an accessible enclosure, so it seems like it should be OK, though regrettably not as pretty as if the cables were long enough to not require extension.

4. But if it's not NEC compliant, I guess I can make these splices in a few junction boxes (using volume calcs to determine how many splices I can fit in each j-box) that sit off to the side of the main panel. Any particular requirements on distance from main panel these j-boxes should be, and similar question for distance of outlets mounted near main panel for convenience?

Thanks for any insights.
 

Last edited by PJmax; 08-05-20 at 09:12 PM. Reason: resized pic
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Old 08-05-20, 09:22 PM
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1) That is a 2P40 amp breaker. If you pried the tie handle off it would say 40 on both breakers.
Same thing with a 20A breaker.

2) Most NM connectors can accept two NM-b cables. They also make twin connectors which are easier to use. A 12-3 would go in a single connector.

3) Yes.... you can splice on tails to reach the breakers. If you make a neat splice and keep the wirenut in the back all should look pretty good.

4) You can mount a receptacle directly below or beside the panel. We usually use a 1/2" offset nipple for that.

 
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Old 08-06-20, 01:13 AM
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Another option is to raise the panel so you have more conductor inside the panel.
 
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Old 08-06-20, 08:11 AM
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I'll have to mount the new panel higher than the old panel, but the distance between top of the enclosure and the breakers is much greater for new panel. Kind of limited to how high I can place panel because still need a little room above panel to secure cables to wall before they enter panel. Even if I eek out a few more inches than I'm currently planning (which would probably violate code with respect to height of panel mounting location), I'll still need to splice a number of cables (though it would save splicing on a few)..
 
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Old 08-06-20, 01:34 PM
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Some panels are rated flippable, top to bottom. Some folks prefer to minimize the unfused service wire inside the box. If your new panel is reversible, and the service is coming in low, and most branch circuits exit high, I'd consider the flip.
Note also, there is a spec on maximum breaker height above the floor.
 
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Old 08-06-20, 05:55 PM
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The highest breaker can be no more than 6 foot 7 to the center.
 
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Old 08-06-20, 06:21 PM
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Wow, 6'7" max height to highest breaker? That's quite an allowance. Low ceiling basement, so I'm not anywhere near that.
 
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Old 08-06-20, 07:30 PM
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Yes.... the circuit breaker at the top of the box may not be higher than 6'- 7" inches from the floor.
 
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Old 08-07-20, 06:56 AM
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While I'm changing the panel, I'd like to replace the multiple pieces of plywood that have been fastened to the unfinished basement wall (concrete I guess, definitely some kind of masonry) and used to mount the old panel, sprinkler system controller, and outlet box; and replace it with one large piece of plywood that will fit all these enclosures. I'm guessing Tapcons are the correct type of screw type for this application. For fastening 3/4" plywood, what's a good size tapcon - maybe 3/16" x 2"?

For fastening the panel to the 3/4" ply, the idea is to fasten only to the ply and not let the screw tip press into the concrete (and presumably push the ply away from the wall), correct?

For filling the holes in the wall left from the old screws fastening the various pieces of plywood, is there a particular type of caulk I should use, or can I use the GE silicone 1 caulk I have on hand?
 
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Old 08-07-20, 11:28 AM
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I'd go with 1/4" tapcons if the panel mounting holes accommodates that. I have better luck with 1/4 as opposed to 3/16" as regards taking good screw torque. Also, there is some rule somewhere that wants 1/4" spacing (breathing room) from the back of a metal panel to any moist wood. For sure if it mounted outdoors, if indoors likely not an issue unless its pressure treated.
 
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Old 08-07-20, 06:39 PM
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I'd go with 1/4" tapcons if the panel mounting holes accommodates that. I have better luck with 1/4 as opposed to 3/16" as regards taking good screw torque.
I was actually thinking tapcons to secure plywood to wall. Then short screws to secure panel and other equipment to the plywood.

Also, there is some rule somewhere that wants 1/4" spacing (breathing room) from the back of a metal panel to any moist wood. For sure if it mounted outdoors, if indoors likely not an issue unless its pressure treated.
Good to know, thanks. This is indoors so it's not an issue.
 

Last edited by cartman; 08-07-20 at 07:20 PM.
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Old 08-07-20, 07:19 PM
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3) Yes.... you can splice on tails to reach the breakers. If you make a neat splice and keep the wirenut in the back all should look pretty good.
I'm going to attach a ground bar to the bottom of the new panel (compatible bar - both new panel and ground bar are Square D Homeline). I'll have to splice all the circuit cable ground wires to land them on the ground bar. I'll use 12g wire for the splices. Do I have to splice each ground wire individually, or can I splice two (or more?) ground wires that are 12g or less with one 12g [extension] ground wire?
 
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Old 08-07-20, 07:42 PM
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Why not install a second ground bar.
I personally don't like bare wires all over the panel.
I try to keep the ground wires as short as possible,
 
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Old 08-08-20, 07:16 PM
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Why not install a second ground bar.
I personally don't like bare wires all over the panel.
I try to keep the ground wires as short as possible,
The panel comes with one neutral/ground bus on each side. Since this is a main panel, those are bonded, so I could put grounds and neutrals on the same bar, but to me as a relative newb, it's much neater and easier to see what's going on if grounds and neutrals are separated. And separate ground bar on bottom reduces clutter along the sides of the panel.

The old panel had a 12-3 circuit that had the hots wired to 2 different 15A breakers. I'm guessing it was done this way due to space constraints in the panel. This circuit controls bathroom heater and fan. Both hots should be on one dual pole 15A breaker, correct?
 
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Old 08-09-20, 05:52 AM
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If both hots landed on the same equipment the hots need to be disconnected at the same time. A 2 pole breaker would accomplish this.
 
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Old 08-09-20, 08:59 AM
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Both hots should be on one dual pole 15A breaker, correct?
OR.....use the existing single pole breakers and add an approved handle tie for the preferred way of handling a multiwire branch circuit. This gives you the required common disconnect while a common trip is not required.
 
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Old 08-09-20, 11:53 AM
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OR.....use the existing single pole breakers and add an approved handle tie for the preferred way of handling a multiwire branch circuit. This gives you the required common disconnect while a common trip is not required.
So what happens when one breaker trips? The breaker it's tied to doesn't trip and line remains hot?
 
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Old 08-09-20, 12:28 PM
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Here are a few images of the use of junction boxes.
Depending on how many wires that have to be extended you could end up with a lot of splices in you main panel.
I like the idea of a cleaner main panel.



 
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Old 08-10-20, 11:01 AM
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So what happens when one breaker trips? The breaker it's tied to doesn't trip and line remains hot?
If you have a problem on one of the two circuits, just that one breaker trips so it is easy to identify which circuit you need to work on and yes, the other breaker does not trip and that circuit remains in operation. It is permissible to use a 2-pole breaker, but when that problem on one circuit occurs, both poles trip and then the troubleshooting fun begins just to identify which circuit has the problem.
 
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Old 08-10-20, 01:27 PM
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If you have a problem on one of the two circuits, just that one breaker trips so it is easy to identify which circuit you need to work on and yes, the other breaker does not trip and that circuit remains in operation. It is permissible to use a 2-pole breaker, but when that problem on one circuit occurs, both poles trip and then the troubleshooting fun begins just to identify which circuit has the problem.
So the breaker trips internally, but can't trip the handle because it's tied to the non-tripped breaker's handle? If that's the case, once you notice the circuit isn't functioning, you go to the panel and see both handles in the ON position. How do you determine which breaker has tripped?
 
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Old 08-10-20, 01:39 PM
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Here are a few images of the use of junction boxes.
Depending on how many wires that have to be extended you could end up with a lot of splices in you main panel.
I like the idea of a cleaner main panel.
Thanks for the pics, that makes it easier to visualize what it would look like. I like it. May end up doing that myself, but since it's more of an aesthetic issue than a safety or NEC code issue, it's going to be low priority. But for sure, it looks better to me than a main panel with lots of splices.
 
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Old 08-15-20, 10:39 AM
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So the breaker trips internally, but can't trip the handle because it's tied to the non-tripped breaker's handle? If that's the case, once you notice the circuit isn't functioning, you go to the panel and see both handles in the ON position. How do you determine which breaker has tripped?
When using a 2 pole breaker when either pole trips, the other pole also trips internally. When using an approved handle tie on two adjacent single pole breakers, one breaker can trip to the center position and the handle tie is still connected to the other breaker in the full "On" position. But, when you simply turn off either breaker, the other breaker goes with it. The NEC requires that common disconnect when manually turning the circuits off and on, but a common trip isn't required.

If you cannot visually tell which breaker has tripped, carefully feel each handle and the tripped breaker's handle will be very loose.
 
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