Can I consolidate conduit going into an outdoor sub-panel?

[Tim Fastle]

I have an outdoor sub-panel that I am going to add 3 circuits to for various outdoor plugs around our front yard. I have the conduit installed and ran to the panel but would prefer, from an aesthetics perspective, not having 4 different (these 3 plus one existing) runs of conduit running up into the panel. Can I take them all into a J-box of some sort near the ground and gather the 9 wires there and run them all into the panel via 1 larger conduit? I am guessing not since I have never seen it done (yes, I am aware that I am the only one that thinks I have seen everything). Or, is there a way that this is done - to consolidate the wires into one conduit before entering the panel? There are three 3/4" pvc conduits that all come together right below the box.

Thanks in advance.

 

[wwhitney]

Generically you can combine the conduit runs at a junction box and run the circuits together in a single conduit into the panel. The issue is whether doing so would require you to upsize some of the conductors for the combined portion. To determine that, you need to specify for each circuit the wiring size and count, insulation type, OCPD size, what the load is, and the length of the homerun that will be combined vs the total homerun length.

Cheers, Wayne

 

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[Tim Fastle]

Just so I am clear, what you are describing is actually connecting the wires together in the junction box and making them all the same circuit with the same breaker, correct? More what I was thinking was to just route the wires from the 3 conduits into a junction box (or something like a j-box) and funneling them into one (probably larger) conduit up to the panel. Then, in the panel each circuit would be wired with it's own breaker in the same manner had it come into the panel in it's own conduit. Truthfully it's not a huge deal to me but it just seems like it would be a much cleaner set up.

Thanks very much for the reply and input!

 

[wwhitney]

Just so I am clear, what you are describing is actually connecting the wires together in the junction box and making them all the same circuit with the same breaker, correct?

No. I responded to the question you intended. But how much current a conductor is allowed to carry depends on factors including how many conductors are within the conduit along with that conductor.

Cheers, Wayne

 

[Tim Fastle]

Ah, that's very interesting and I appreciate the clarification. Is there a calculator out there one can use for such a purpose?

Basically what I have is a sub-panel 100' from the main box fed by four 8 gauge AWG THHN (2 hot, 1 com, 1 ground). There is a gfi receptacle on the pole of sub-panel, I think 12 gauge THHN. I am adding 3 circuits, 2 about 50 feet and the third about 75 feet, all will likely be 10 gauge THHN. All 4 circuits in the box will be 120v on 15amp beakers with a GFI receptacle at the end of the circuits. The sub panel is protected at the main via a 30 amp double pole breaker. The feed to the subpanel is 1" pvc conduit and the circuits are all 3/4" pvc conduit - all schedule 40.

I am not talking about a shop or a lot of heavy equipment, just plugs around the property to plug Christmas lights into, a charger for my gate opener and a power tool from time to time. Is this something an experienced electrician would look at and clearly see that it's no problem to combine the wires (or is a problem) or does it require a lot of calculations and might be iffy? If, in my circumstance, funneling a couple of the runs together before running them into the box was fine to do I just might. If it's a problem or a huge hassle to figure out - I'd just run them all into the panel.

I do appreciate the information and input!

Thanks

 

[Fitter30]

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[wwhitney]

Basically what I have is a sub-panel 100' from the main box fed by four 8 gauge AWG THHN (2 hot, 1 com, 1 ground). . . .

So most (all?) THHN wire is dual-rated THWN-2, which is important as you need the W in the rating for outdoor (wet) use.

As to combining 4 circuits in one conduit, you've already upsized all the wires for distance / voltage drop, so you'll have no issue with ampacity.

As for conduit fill, a 3/4" PVC Schedule 40 conduit with THHN/THWN-2 conductors has room for (9) #10s, so that's just enough for (6) #10s (3 new circuits), (2) #12s (the existing circuit), and a single #10 EGC shared by all the circuits.

If one box has (6) #10s coming in and (6) more going out, (2) #12s coming in to a receptacle, and (1) #10 EGC coming in and (3) more going out, then the minimum size for that box is 13 * 2.5 + 4 * 2.25 = 41.5 in^3.

Cheers, Wayne

 

[Tim Fastle]

Thanks very much Wayne .... I think I now have a handle on it and will proceed accordingly!