How do I best route multiple lines into subpanel

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Old 05-27-18, 12:33 AM
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How do I best route multiple lines into subpanel

This is my first post in this forum. Thanks in advance for the help. I am doing a home remodel with new addition, requiring seven new electrical circuits. The existing main electrical panel is full, so I am installing an external subpanel behind the main, since there is no room in existing utility room. The wires are all secured to joists in crawl space and I was planning on routing them all through 2 1/2 in. PVC conduit from the crawl space to the subpanel, about two feet horizontal and then four vertical. As I understand though, I cannot run all the wires directly into the subpanel with this conduit, as the wires must be secured, no more than two per knockout, upon entry. So my question is: can I run the 2 1/2 in. conduit into a large junction box below the subpanel and then pairs of the wires through 4 separate short runs of 3/4 in. conduit between the boxes, or will I need to scrap the larger conduit and just run the 4 runs of 3/4 in. the entire way from the crawlspace? Or is there another way that I'm just not considering? I prefer the larger conduit if that's correct, as then I can run additional lines more easily in the future if necessary. Thanks again for any advice!
 
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Old 05-27-18, 02:51 AM
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The wires are all secured to joists in crawl space
Following assumes not wires but cables.Wires must be on continuous cable.

I was planning on routing them all through 2 1/2 in. PVC conduit from the crawl space to the subpanel, about two feet horizontal and then four vertical. As I understand though, I cannot run all the wires directly into the subpanel with this conduit, as the wires must be secured, no more than two per knockout,
If run in conduit ending in the panel no clamps needed. Just be sure to secure the cables close to where they enter the conduit.
 
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Old 05-27-18, 04:20 AM
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It will be less work to bring the cables directly into the panel. No need for splices. You also would not have the derating issue.
 
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Old 05-27-18, 07:22 AM
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Hi, why not just run the cables directly into the panel, am I missing something?
Geo
 
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Old 05-27-18, 11:26 AM
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Clarification

Thanks for the help and sorry if I wasn't clear on my initial post. This will be an exterior subpanel, and multiple cables will run from the crawl space and then exit along an exterior wall into the bottom of the subpanel. My understanding is that since they are entering in this manner all cables must be secured upon entry with no more than two cables per knockout. I'm just trying to do this most efficiently, hopefully drilling just one large hole for conduit out of the crawl space, but an not sure how best to proceed from there. I'm completely open to any suggestions. Thanks again.
 
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Old 05-27-18, 11:44 AM
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Can you install the sub in the house so the cables don't need to go outside?
 
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Old 05-27-18, 12:28 PM
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No unfortunately there is not enough room inside to mount box.
 
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Old 05-27-18, 01:34 PM
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How about mounting a J box in the crawl space and bring the new NM B cables into it then switch over to THHN and bring them into the back of the new panel through the exterior wall using a smaller PVC.
Geo
 
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Old 05-28-18, 08:55 AM
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So I was originally intending to install a junction box in the crawl space and switch to uf-b cables from there into the 2 1/2 in. conduit, but i would be ok with transitioning to THWN there too and smaller conduit. But can I run that many THWN wires from one conduit directly into the bottom or side of the exterior subpanel? On a side note, if I switch over to THWN, can I then run a single ground from the junction box to the subpanel?
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Old 05-28-18, 09:23 AM
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What sizes are these 7 circuits ?
 
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Old 05-28-18, 09:33 AM
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Conductor size

what size cables are you using for the new circuits one ground conductor is fine as long as it is the same size as the largest circuit conductor.
Geo
 
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Old 05-28-18, 10:14 AM
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Conductor size

The largest is 10 AWG., The rest are 12.
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Old 05-28-18, 10:29 AM
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When we used a big “J” box we would install a ground strip inside and connect all the ground to that, how many 10’s and how many 12’s ?
Geo���� https://www.homedepot.com/p/Square-D...TACP/202353315
 

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Old 05-28-18, 05:06 PM
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There are two 10s and five 12s. I was anticipating excess capacity for inevitable future lines.
 
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Old 05-28-18, 05:30 PM
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Hi, I would run 2 - 3/4 schedule. 40 PVCs from the J box and split the circuits between them.
Geo
 
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Old 05-28-18, 07:11 PM
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To expand on Geochurchi,

I agree, two 3/4" conduits. Run your hots/neutrals, keeping the pairs together using THHN/THWN. Wirenut each circuit to the existing NM-B runs.

Run one 10ga green or bare wire for your ground and either wire nut or use a ground bar to connect all of them.

Easy peasy!
 
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Old 05-29-18, 07:06 AM
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Great! I like that solution. Thanks for the expert advice! So do all the THWN wires entering the bottom of the subpanel from the 3/4" conduits need to be clamped? Or is that not necessary if all NM-B cables are secured just prior to entering the j-box? And if they do need to be clamped at the subpanel, what is the maximum number of THWN wires per clamp? Also, they are short runs of conduit, but any suggestions on how to best run the wires through? Should I run one pair at a time to keep track of each circuit, or would it be easier to tape and mark each pair, bundle and run all wires at once?
 
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Old 05-29-18, 09:36 AM
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Conductors in conduit do not use clamps.

Pair the wires with a wrap of tape on both ends. You could also use labels on each pair.
 
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Old 05-29-18, 11:27 AM
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No need to clampTHWN , maybe some tie wraps to keel them nest in the panel, pull all of the conductors at once and identify with tape or stick on numbers

Geo
 
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Old 05-29-18, 12:55 PM
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Great. Thanks for all the help!
 
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