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Discussion Starter · #1 · (Edited)
Bringing this question back to the top because I never got an answer about protecting the feeder cable.

I'm installing a sub-panel beside the existing panel. In the 2nd picture, the part of the feeder just dangling will get attached to the 1x3 located below and to the right of the sub-panel. This 1x3 just happens to be nicely inline with a knock-out on the lower left-hand corner of the main panel.

Other than attaching the feeder to the surface of the 1x3, does it need to be protected in any other way?



[Start of Original Question]

I've made the decision to chunk the http://www.diychatroom.com/f18/unorthodox-sub-panel-62937/ and instead install a proper sub-panel by the existing breaker box. That way, I won't have any issues with running out of room in the existing breaker box as I finish in the basement, and gives me extra room to run some additional circuits I've been wanting to do.

At the moment, the main question I have is placement of the sub-panel. I know that all panels must have a free work space of 30"x36"x6'6", and I've been told that the panel doesn't have to be centered in this free space. But in my case, to best fit the sub-panel along side the main panel, I have to place the sub-panel at the very edge of the work space. Would an inspector likely turn this down?

Attached below is a picture of the mounted sub-panel. The white wall is cinder-block. The work space is 2x4 framing from the block to the garage door. What you might not be able to tell from the angle of the picture is that the storage shelves beside the work space stick out to the very edge of the cinder block. The angle makes it look like the sub-panel over-laps the edge of the cinder block, but in reality, there is a small gap. The face of the sub-panel sticks out 1" past the edge of the cinder block, but because of the support tubes on the shelf, the panel doesn't block any access to the shelf.

Other wise, I believe I know what to do to wire up this sub-panel, but I wouldn't mind a review of the plans just to make sure there isn't some small detail I'm overlooking.

For starters, the main breaker is a 150 amp panel with 32 slots (only takes 1" breakers). The sub-panel is a GE TLM812FCUDP 125 amp panel with 8/16 slots. http://www.acehardwareoutlet.com/(od2hz355khi3xkud2nafds45)/ProductDetails.aspx?SKU=32777. I'll add a GE 100 Amp Double Pole breaker at the bottom of the existing panel, then use a few feet of 2/2/2/4 copper to connect the breakers to the panel. I've verified that the ground bar will accept #4 wire, and the breaker is supposed to be able to accept #6 to 1/0 size copper wire.

I know that in the sub-panel, I keep grounds and neutrals seperate, only one neutral per screw on the neutral bar, but I can put two grounds per screw on the ground bar IF they are the same size.

As for the load, I don't have any specific appliance type circuits that will be on the sub-panel. Instead, it will only be for lights and outlets for the new rooms in the basement, as well as some new 20 amp outlets in existing bathrooms (the existing bathrooms were build with only 15 amp circuits). I won't come anywhere close to filling it up, and since some of the new rooms require AFCI breakers, all the breakers in the new panel will be 1" breakers (i.e. 8 circuits or less on the sub-panel).

BTW, no J-B Weld was used to mount the sub panel (or should I perhaps add some, just to make sure it doesn't come off those 2x4's its mounted to). What you can't tell very well from the picture is that there is a 2x4 on the edge of the cinder block (the 2x4 is painted white). I used something like 16d nails to attach some 2x4s from that white stud to the next stub about 6" over. I've got something like 1/4" hex lag bolts through the mounting holes to attach the sub-panel to the 2x4s. Since there was only one mounting hole in the top, I added a fender washer. The existing panel is mounted on 1x4s. By mounting the sub-panel on 2x4s, its shallower depth means the faces of the two panels are just about flush with each other.
 

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I'm pretty sure you can have other electric panels in the restricted space

There is a Max size sub you can run off a Main panel, not sure what that is in this case
 

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Discussion Starter · #3 ·
In the research I've done so far, I haven't seen any references to any limits beyond doing load calculations. I followed the instructions provided in a reference book my inspector suggested I get. But by the calculations, the addition was nil because the only new load is only lights and outlets for the additional sqft being added to the house.

Other wise, I could see where codes might say something along the lines of a the main breaker supplying the feed to a sub-panel can not be more than say 80% of the original breakers supply rating (i.e. if the main panel is 150 amps, the sub-panel can not exceed 120 amps). However, the reference guides I've read, and even doing some more Googling on the subject have failed to turn up any such limit so far. I even came across one post that said the rating of the sub-panel can match the rating of the main-panel. I guess the idea there is that the sub-panel is already protected by the main breaker in the main panel. If such posts are to be believed, that would suggest the only limit is that the sub-panel must be protected within the rating of the sub-panel.

However, this whole question is making me realize that one thing. I need to backup and do a load calculation on the whole house, include the new space and account for a larger A/C unit recently installed, make sure I'm not exceeding the capacity of my main breaker.
 

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Discussion Starter · #5 ·
Here's the information from the label on the main breaker box:


GE PowerMark Gold Load Center 10055274P17

Type 1 Indoor Enclosure
Front Cat. No. TM32C
Use with GE LoadCenter Enclosure Cat. No. TM3215CCU
Main Rating: 120/240 VAC, 1 Phase, 3 wire, 160 Amp Maximum

Use Only GE type breakers:
THQL, THHQL, TQDL, THQDL, or TXQL


I would ASSUME that this means the bus has a maximum limit of 160 amps; therefore a 125 amp panel protected by a 100 amp breaker would be fine.

Or are you saying that the breaker could have one maximum limit value, and a different "pass-through" value (i.e. the maximum amount of current that can travel the FULL length of the bus)?
 

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I see you don't have much room there, but if I was running 100 A to a sub panel I would use at least a 20 space panel. For a little 8 space, I'd probably only run a 40 or 50 amp feeder and save some money on wire and feeder breaker. (doesn't sound like the load is that great) The price jumps dramatically above 60 amps for breakers. This is only my opinion, you can do as you wish.:thumbsup:

As for the max size allowed, the NEC code stays silent on. You just need to provide enough capacity calculation wise.
 

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ould have one maximum limit value, and a different "pass-through" value (i.e. the maximum amount of current that can travel the FULL length of the bus)?
Panel's bus bar fingers have a max rating of which is the largest breaker that you can snap in. Most residential panels each tab is rated at 125 A, which means that for example, the biggest double pole breaker you can use would be 125 A. The panel manufacturer would then use a different style breaker for sizes above the limit, and may take 4 spaces for 1 double pole. (so each pole would contact 2 buses)

The total bus rating is limited by the bars own ampacity, which is usually the rating of the panel.
 

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Discussion Starter · #8 ·
I see you don't have much room there, but if I was running 100 A to a sub panel I would use at least a 20 space panel.
The new panel allows for 1/2" breakers, so if I REALLY needed more space, then I could say that I have a 16 panel breaker.

Facts are that I wasn't off by much. The existing breaker box had enough room if it wasn't for the fact that I've added two circuits for a workshop, and I want to run a second circuit to the current bathrooms so that I can install at least one 20 amp outlet in each (getting tired of having to choose between lights and the hair dryer).

Actually, I sort of fought adding this sub-panel because It's going to be about a $100 cost, and I could have gotten by with the existing panel if I combined the workshop lights circuit with the basement circuit, and forgo the notion of new 20 amp outlets in the bathrooms (i.e. $100 is a lot of money just to avoid occational breaker trips while using a hair dryer).

But my present and foreseable future needs can be met with the addition of the net 6 full size breakers this small sub-panel gives me (8 openings minus 2 to add a 100 amp breaker to existing panel).


I had already noticed the price jump once you get above 60 amps. I considered just wiring this panel with a 60 amp breaker, but I wasn't too sure about doing that since my plans will likely call for placing about 6 20amp circuits in the sub-panel (i.e. twice the 60 amp breaker). The other thing was that a 60 amp breaker would limit the size of the feeder wires. The 100 amp breaker is only going to cost about $20 more and will allow me to wire the panel up such that with 16 possible circuits, I'll have more than enough power.

As for the cost of the feeder wires, the local Lowe's has copper 2/2/2/4 for about $5/foot. I checked the length I'll require going from the bottom of the current box to the top of the new one. 5 feet will be more than enough (could do it with 4 feet if I wanted to push it). So I figured $25 was a cheap investment to prevent me from ever having to upgrade any aspect of the sub-panel.


Thanks for the info on the breakers. Basically sounds like as long as the existing panel will accept the 100 amp breaker, I'll be good to go as far as the rating on the main panel. Given that the 100 amp breaker is a THQL breaker, based on part numbers, it sounds like it's going to fit.
 

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Discussion Starter · #9 ·
Securing and Bending SE feeders for Subpanels

Any guidance on code requirements for securing Service Entrance feeder wires for a subpanel? What about guidance on how tightly you can "attempt" to bend them?

In my case, my question is specifically in relation to the subpanel I'm trying to install here. However, I'm making this a new question because when I attempted a search on the subject matter of "securing SE", I couldn't find anything.

Merged with existing thread
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I've learned that code sometimes has different rules depending upon the size of the cable. For example, NM cables can not run on the underside of floor joists unprotected. But that rule suddenly doesn't apply when you start getting into larger cables like #8 size and greater. Interestingly enough, my guide book indicates that NM cable must be secured within 12" of an outlet box (334.30), yet the rule apparently changes to within 8" on non-metallic boxes without cable clamps (314.17(C)).

So I'm trying to figure out the following:
1. What are requirements for securing these larger cables (SE, SER sizes) for sub-panel feeders?
2. What do you use to secure them with? (besides NM clamps on the panels).
3. How sharp can you bend the wires?

In my case, the best means of getting feeders from the main panel to the sub-panel are to exit the main panel through a knockout near the bottom left, go under the sub panel and loop behind the subpanel, and enter the subpanel through the top. But that is going to require a pretty small size U bend relative to the size of the cable (in my case, I'm trying to use 2/2/2/4 copper).
 

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Please keep questions on the same install under the same thread
This is already the 2nd thread on this sub-panel
No need for a 3rd thread

Thanks
 

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Discussion Starter · #13 ·

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That thread was about a 60 amp 2/4 breaker panel I wired up years ago.
This thread is about a bran new 125 amp 8/16 breaker panel.

The two are ONLY related by the fact that once I've got the 125 amp panel installed, I'll no longer require the old 60 amp panel.
Attached below is a picture of the mounted sub-panel


So the picture in this thread is NOT the current 60a sub ?

If everybody started as many threads as you do about the same project this board we be flooded
Keep one thread going on your project
In the future I will merge threads that are on the same subject back to the original thread

Thank you
 

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Discussion Starter · #15 ·
Correct. The picture is of the new 125 Amp sub-panel.

I've already taken enough jabs from my posts on the J-B Weld (a question about a handy box) and 60 Amp sub-panel (the UNorthodox Sub-Panal) I wasn't about to include images of the 60 Amp panel for people to poke fun at.

I sorry if my starting of a new thread on "Securing SE Cable" was poluting the thread pool. That wasn't my intension. I only intended to create a searchable trail of bread crumbs on that subject, because I couldn't find anything on the topic when I searched this board and Google on the subject.

Speaking of which, I did find an answer to at least one of the questions. I found in "Code Check" where it references the need for SE cable to be attached with 12" of the entry point (in this case, presumably the NM clamp on the box).
 

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Discussion Starter · #16 · (Edited)
OMG, I didn't know what I was getting into when I choose to use 2/2/2/4 cu for the feeder of this sub-panel. It took me well over an hour to simply connect 4 wires to the panel. Here's the current results (a pair of breakers are shown already installed to insure I had clearance attaching the neutral).

I should be able to meet the 12" rule by finding some way to attach the cable comming out of the sub-panel to the ocx/stud behind the panel. Not sure how yet as the wire is wedged into the corner from the "spring" effect of making that U bend. Since there isn't any room to get any sort of staple behind the cable to attach it to the 2x4 stud on its left, I guess I'll need to staple it to the OSB panel.

I'm feeling pretty good about being able to get the other end of the cable into the main box. The entry point on the main box is right inline with the 1x3 you see at the bottom of the image. I'll be able to secure the cable to the 1x3 as well. Bends to the SE cable going under the sub-panel will go real smooth. I was able to cut the edge of the 1x3 to a 45 degree angle (you can see the fresh sanding marks in the picture) and there is another 45 degree cut on the back side of the bottom 2x4 supporting the sub-panel. The angles are really cutting down the pinch points on roughting the cable under the sub-panel.

Assuming I can find any suitable staples to secure the SE cable, about the only outstanding question I have in my mind is whether anything needs to be done to protect the cable through the U bend. It doesn't seem to need any protection just based on how big and stout that cable is. But it just seems odd having a cable capable of supplying so much power being within easy hand's reach. I guess once everthing gets wired up, I could find some way to cover all the wires comming out of the top with some sort of panelling... sort of making the top side of the sub-panel look flush mount... after the fact.
 

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You could have taken that cable in from the bottom.
Are you covering the panel in any way?
Is that an outside wall?
If that was an outside wall, just a peice of scrap wood behind the cable to protect any nails from the outside, but that is not a code requirement.

I have been to homes that had new sidnig installed and the nails penetrated the jacket, but not the wires.
 

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Discussion Starter · #20 ·
You could have taken that cable in from the bottom.
With the position of the lug nuts, I pretty much had to come in from the top. But I still have the option of flipping it over. Either way leaves me 6 knockouts for circuits out of the top/bottom. I might even have to flip it over because I want to lift it higher so that the branch feeders coming out the the box will be above eye level more like the original panel is.

Are you covering the panel in any way?
Just with the door that came with it. Otherwise the plan is to keep this wall unfinished.

Is that an outside wall?
If that was an outside wall, just a peice of scrap wood behind the cable to protect any nails from the outside, but that is not a code requirement.

I have been to homes that had new sidnig installed and the nails penetrated the jacket, but not the wires.
It's an outside wall, but the otherside is brick. So I don't see protection from the outside as being an issue. I was concerned about if protection from the inside was required. Exposed MN seems to be ok in an unfinished garage, but I didn't know if the same held for SE cable going to a sub panel.
 
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