Home Wire trough and conduit size!!

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  #1  
Old 02-13-12, 05:06 PM
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Home Wire trough and conduit size!!

Hello,

I'm replacing my main panel with a 100 amp breaker alone ( disconnecting means ) and running out of their to my sub panel, 30 feet away which will supply all the circuits, reason: location wasn't a good place, but needed within 6' from outside meter, so I decided to make a sub panel that supplys the house circuits.

Above the sub panel, I want to put a trough or junction box to bring all the romex's into the closure and then pipe down to the sub panel. My problem is sizing the pipe from the trough to the sub panel and sizing the trough. I've been searching the code book and still not sure on what I should do, I don't need it inspected, cause I haven't changed the amp size of the panel and kept it 100 Amp panel.

Details:
I have a 24 slot circuit panel, 2 which are 30 amps, 2 are 20 amps and the rest are 15 amp breakers, i'm rewiring the house with 2-12 w/ground wire conductors besides the 30 amp
breakers which are 2-10 w/ground conductors.


2-#10 wire romex - 2 cables, total wires = 6 Total wires with grounds.
2-#12 wire romex - 22 cables, total wires = 66 Total wires with grounds.

72 Total wires, 6 of them are #10's wire size

My idea to minimize the size of conduit would to put a ground bar in the trough and run an #8 ground in the conduit to the sub-panel,
so my new total would be: 51 Total wires.

So my question would be:
What size conduit would I need from the Trough to the Sub-Panel and what size Trough will I need?

Reason:
I'm doing the trough is because it will look cleaner and more professional regardless of the cost. Using all #12, I think is safer and if I need to upgrade, then it will be available. Also since this doesn't need inspected, I still want to do it right and without problems or fires.
 
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  #2  
Old 02-13-12, 05:51 PM
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Welcome to the forums!

If your rewiring the entire house, why not just run all cables to the new sub panel?
 
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Old 02-13-12, 06:38 PM
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I think a picture of your existing installation would be quite helpful.

Is the new panel going to be inside or outside? Is the planed gutter indoors or out? IF you are planing to mount a disconnect, I assume outside, why can't you just do a Meter/panel combo?

The smallest gutter I have seen is 4" x 4"
 
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Old 02-13-12, 06:38 PM
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The trouble you will run into running a larger conduit instead of multiple smaller conduits is you will need to derate based on the number of conductors in the conduit. You could end up with only 50% of the normal ampacities.
 
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Old 02-13-12, 08:23 PM
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Ya, someone told me to run 3 - 1 inch conduits because of derate! will that work? 1 pipe work look a lot nicer. Because I'm coming out of the right side of the panel.

I not rewiring everything, just wire and devices, meaning, I'm not going to get into the outside and have to relocate the meter, knowing that your limited to certain distance within the meter base and panel. also getting the electric company involved.


Its not going to be a disconnect, just another small 100 amp panel for over-current protection, and fuses can be expensive.

Besides that, what size trough would I need with 24 circuits ( romexs ) to come into the trough? I looked at the code and still confused! I'll keep researching if I don't get the answer.
 

Last edited by niaown; 02-13-12 at 10:40 PM.
  #6  
Old 02-14-12, 08:20 AM
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NEC Art 376 (2008) covers metallic wireways. Section states that you do not have to derate until the current carrying conductors (everything but the grounds in your case) exceeds 30. You may also only fill the gutter to 20%. I suggest using THHN wire rather then Romex as Romex will fill a gutter VERY fast.

With conduit you will have to start derateing after 3 wires (80%) (310.15(B)(2)(a) but if you stick to 9 or less wires in a pipe the derateing will not exceed the small conductor overcurrent protection rule (240.4(D) 2008) and therefore have no effect.
 
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Old 02-14-12, 10:01 AM
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Reading that is like reading the bible, its very difficult to understand. From what I understand, correct me if I'm wrong, but I'm bringing the romex into the sides of the trough ( gutter? ) stripped off the romex and have conductors only course, which the wires are THHN, and pulling single conductors down the pipe into the panel.

9 wires or less in a conduit out of 51 wires, that's a lot of conduits! 2 inch conduit emt wouldn't be big enough? wow! single conductors.
 
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Old 02-14-12, 10:05 AM
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but I'm bringing the romex into the sides of the trough ( gutter? ) stripped off the romex and have conductors only course, which the wires are THHN,
Best practice is not to strip the sheath off NM-b. The wires in NM-b are not considered THNN because they are not marked or approved for use except in the sheath.

Also note if you use THHN as suggested you only need one ground wire per conduit. You do not need one ground wire per circuit. so that reduces your actual fill.

2 inch conduit emt wouldn't be big enough? wow! single conductors.
1" EMT is rated for 45 #12. 2" 101 #12.
 

Last edited by ray2047; 02-14-12 at 10:20 AM.
  #9  
Old 02-14-12, 10:38 AM
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While 1 1/4" EMT would be allowed to run 45 #12 THHN's, the derateing would cut the actual current carrying capacity to 9 amps each. That is not going to work.

As Ray mentioned, you can not strip the cable jack off NM-b and call it THHN. My suggestion is to run the Romex into the gutter using approved connectors, bond the grounds to the steel wireway as required, splice it to THHN wire, and run the THHN to your new panel. Run the gutter above the new panel and install a series of 1/2, 3/4 or 1" EMT down into your new panel. If you keep these pieces of EMT shorter then 24", there are no derateing factors as they are considered nipples.

Also, if you bond the grounds to your steel gutter, and install EMT to your new panel, you do not need to run any grounds as it will all be bonded together. You can run a ground wire if you want though.
 
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Old 02-14-12, 12:03 PM
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Ok! i'll try to explain this the best I can without a picture, try to imagine this!
I have a 1-1/4 conduit run around the wall for the feeder with back to back 90's uncut into the center/top of the panel, tight against the corner of the wall, so I only have room to bring the conduits up the right side, top and right side of the panel to bring up the conduit(s). My idea is to make it look nice, my thought was to bring 1 conduit out of the side of the panel with a LL fitting and straight up with a 90 degree bend to the right into the floor joist, instead of bringing a lot of conduits up, looking weird, meaning I like a balanced looking panel, ya know what I mean, its going to be my entertainment room for the guys! Not that its more important than safety, but just to look nice also.
Also, I was told that no matter the distance, you should always have a ground wire in a conduit no matter if its bonded or not!

24 slot panel
2 - 30 amps
2 - 20 amps
18 - 15 amps
2'' conduit won't work? with single conductors? 1 ground #8
If not, then I could run 2 - 1-1/4 maybe, confusing!
 
  #11  
Old 02-14-12, 01:52 PM
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While 1 1/4" EMT would be allowed to run 45 #12 THHN's, the derateing would cut the actual current carrying capacity to 9 amps each. That is not going to work.

I posted again what I mentioned about 1 1/4" pipe. Your derateing will cut the amperage carrying capacity of the wire down too much to be useful.

I always agree with making it look professional. How about posting some picts so we can see what you see. Maybe there is another way to do this.

Also, I was told that no matter the distance, you should always have a ground wire in a conduit no matter if its bonded or not!
Tell that to the millions of feet of pipe installed in commercial buildings that has no separate EGC. EMT and other approved wireways are listed for grounding.
 
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Old 02-14-12, 04:30 PM
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Ya I understand that Ironhand, thank you, but I'm having mixed sizes and #10's and #12's
Do I have to size the conduit with #10's even though there will only be 4 #10's? or that won't make a big difference?
I think the maximum size I can fit in that panel that would look half decent would be a 2'' pipe, but that probably won't work.


Pictures are available, I tried my best to give the most info.



 
  #13  
Old 02-14-12, 07:32 PM
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You'll need a bonding bushing where the 1 1/4" conduit enters the top of the loadcenter instead of the plastic insulating bushing because you are entering the panel through concentric knockouts and you aren't removing all the rings in the factory punched knockouts. Here's an idea. Why not get a 90 degree fitting for the trough and turn the trough down and run another length of trough alongside the loadcenter. Then you could punch holes and use chase nipples to join the trough to the panel for the wires to pass, eliminating any more conduits. (My opinion is I would just run the NM-B cables directly into the panel with no trough)
 
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Old 02-14-12, 08:14 PM
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Why not just extend the trough to the left until it is over part of the panel? That way you could run a 24" or less nipple to the panel and the derating issue goes away. I also like the L fitting on the trough idea.
 
  #15  
Old 02-14-12, 11:15 PM
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Does anyone see any problems with this installation?

Is the 2'' inch conduit to big? or should I go to 1-1/2 or 1-1/4? Since I have mixed sizes of conductors!

Since I'm within my distance and I don't need to derate anymore, can I bring all the conductors w/grounds down the conduit from the trough? ( On the other side of the trough, I'm bringing all the romex cables into romex connectors and stripping the sheathing to pull more easy down the conduit. I would not like to terminate any wires in the trough, because of the spacing and will be hard to work on because of the joist spacing. )

What size metal trough would I need?

Since I have a 2 conductor #10 w/ground wire that feeds my Dryer, would I land the Ground/Neutral wire ( Bare Copper ) on the ground still? Or do I need to change that wire to 3 Conductor #10 and change the Receptacle as well?





Why not just extend the trough to the left until it is over part of the panel?
Because the Trough Opening will be facing down, so I can access the trough!



(My opinion is I would just run the NM-B cables directly into the panel with no trough)
See the one existing old panel picture, I don't want wires hanging everywhere or even seeing wires where kids or anyone can see or touch. I would just like a clean looking panel, even in the future if I decide to sell, might catch the buyers eye!
 

Last edited by niaown; 02-15-12 at 12:04 AM.
  #16  
Old 02-15-12, 09:28 AM
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IMO, nothing makes a sloppy looking panel more than pipes/cables coming out the side of a panel.

My suggestion is similar to PCBoss. Move your 1 1/4 pipe/feeder to the left side. (you will likely find a KO big enough on that side) Place a large pull box (opening facing out from the wall) above your panel and skip the LB/LL's. Straight piper coming from the top into the panel will look neater any way. Run your romex's into the pull box and make your splices there.

I can draw you a picture if needed.
 
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Old 02-15-12, 10:38 AM
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My suggestion is similar to PCBoss. Move your 1 1/4 pipe/feeder to the left side. (you will likely find a KO big enough on that side) Place a large pull box (opening facing out from the wall) above your panel and skip the LB/LL's. Straight piper coming from the top into the panel will look neater any way. Run your romex's into the pull box and make your splices there.

I can draw you a picture if needed.
No offence, I appreciate your help, but if you read down, I decided to go with the picture, its my final decision, unless its wrong by code, the trough is going to be hidden like I wrote, i'm not going to redo the panel and have to plug the hole that I already have and drill new holes into the block wall to center the wood. It will look good the way I have it drawn. My last post was asking questions to make it by code mainly like I wrote. Splicing 24 circuits in a JB is a mess, A termination block is much neater!
No need for a picture, I understand!

Thank you again!
 

Last edited by niaown; 02-15-12 at 12:19 PM.
  #18  
Old 02-15-12, 07:49 PM
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My last post was asking questions to make it by code mainly like I wrote.
Your mind is obviously made up, but consider this. I have seen chase nipples used like you show and some inspectors may allow it because it looks neat, but you are not effectively grounding the conduit with the chase nipples connecting to the condulet fittings. Chase nipples are a U.L. listed component when they are used with locknuts, not like you are proposing to use them. You probably should replace the chase nipples in your drawing with close nipples and locknuts with plastic insulating bushings. Neither the chase nipples or condulet fittings will bite into the panel can metal to provide an effective ground, but locknuts will.
 
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