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spencerin
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# Posted: 29 Dec 2021 01:57
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I want to run 2 120V circuits to one location 50' away, and another 2 to another location 20' away. I'm planning on using 12-2 UF-B wire for each circuit, and I want to run all 4 circuits through one knockout in the panel to the outside, where they'll be enclosed in one 3/4" conduit body and sched 40 PVC conduit down into the ground 12", and then run as direct-burial wire only (no conduit) from there to their destinations, with each circuit protected by its own GFCI 20A breaker.
From what I can find, this is okay by code. Am I missing anything major? How do I pin down the wires before they run through the knockout so there's no tension on the connections in the panel? I have NM cable staples for affixing them to wood near the receptacles, and I know they make wire clamp connectors, but I typically see those used when individual wires enter/exit junction boxes and not on a "loom" of wires like this. Can I use a rubber grommet around the edge of the knockout to protect the insulation from chafing? If not, how do I handle this?
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Brettny
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# Posted: 29 Dec 2021 06:12
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Through the knock out you use a wire clamp. It goes through the knock out with a nut on the back and clamps the wire with 2 screws and a piece of smooth metal.
The rest of your plan looks fine.
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spencerin
Member
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# Posted: 29 Dec 2021 06:25
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Do they make them in large enough diameters to be able to clamp multiple wires with one clamp?
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WILL1E
Moderator
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# Posted: 29 Dec 2021 08:10
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Well obviously the bigger the knockout, the bigger the clamp. But if this is going to be to code, i'm not sure what the rules are for how many wires can share a knockout/clamp.
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WILL1E
Moderator
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# Posted: 29 Dec 2021 08:22
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Did some digging because i'm in the midst of doing a panel so i was curious as well. Looks like most of the clamps list how many of what size wires they can handle. I found this clamp and it shows in this picture how many it can take. I would assume those listings would pass code but probably should double check.
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spencerin
Member
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# Posted: 29 Dec 2021 10:22
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That's what I'm looking for, but I think those are too small for what I need. Probably need to check out some local electrical supply places as I'm not sure the big boxes sell larger ones.
Interestingly, they make plastic versions of these, which offer some versatility.
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ICC
Member
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# Posted: 29 Dec 2021 10:54 - Edited by: ICC
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Quoting: spencerin I'm planning on using 12-2 UF-B wire for each circuit, and I want to run all 4 circuits through one knockout in the panel to the outside, where they'll be enclosed in one 3/4" conduit body
I get stuck on this part. I measured a piece of 12-2 UF-B by Southwire and it is almost 1/2" wide... measures at 0.466 wide and 0.189 thick.
I don't see how you figure to get 4 of those 12-2 through a 3/4" conduit, even if it is just a short straight run with no elbows.
I would be using buried conduit for the whole run and use THWN wires. You could run 1/2" PVC conduit for each of the runs; 50' one direction and 20'the other, but that would need two knockouts from the panel.
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Brettny
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# Posted: 29 Dec 2021 11:52
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O yes 3/4in conduit is for only 1 12ga wire. 2 at best with no turns or junctions. Why not just run a bigger conduit or two?
Why do these need to be each on there own circuit and what are they running?
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spencerin
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# Posted: 29 Dec 2021 13:38 - Edited by: spencerin
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I strongly prefer to use direct-burial wire because short segments of it will be exposed to air and water. I could probably get away with 3 circuits, but want room to expand in the same conduit in the future.
The conduit-fill calculators I used said I could fit plenty of 12-gauge wires into 3/4", enough for what I want to do. I just realized it probably doesn't account for the insulation jacket, but it doesn't seem like the jacket takes up that much extra room.
One circuit will power a 12V water pump (converted just before the pump), one will power a heat lamp (250W max), and one will power 6' of heat tape (54W?) and maybe a light (60W max). So, the amp draw on each circuit will be low. Am I allowed to use a higher gauge of wire as a result to be able to fit more in the conduit (with matching breakers, of course)? I can go larger on the conduit as well.
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ICC
Member
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# Posted: 29 Dec 2021 13:53
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Quoting: spencerin conduit-fill calculators
The calcs are based on wire like thhn, not wires with insulation that also allows direct burial.
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ICC
Member
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# Posted: 29 Dec 2021 14:25
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Quoting: spencerin want room to expand in the same conduit in the future.
Leave a pull cord in the bundle if you want to have that option. In many cases, it is next to impossible to pull more wires. It can be even worse if lube was used in the original pull as some lubes dry out after time and then act more like glue. The electrician my brother and I used for contractor work would usually run new conduit and wires even if it was going between the same two points. If you think you might want to add you might want to think about pulling the extra right at the start, along with the other wires.
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paulz
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# Posted: 29 Dec 2021 14:34 - Edited by: paulz
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I bought a quart of Gardner-Bender Wire Aide lube just last week, never used it before. I suppose it helped but after pulling wire through 350' of conduit I can't say it was easy. Always pictured being an electrician as sitting there hooking up wires. More like getting the wire in place.
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ICC
Member
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# Posted: 29 Dec 2021 14:44
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Quoting: WILL1E I found this clamp and it shows in
That type of clamp is meant to secure the wire at the box penetration. The wire outside the panel/box is then stapled to the wall framing. It cannot be used to clamp wire that is passing out and into conduit. There is no clamp for that.
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ICC
Member
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# Posted: 29 Dec 2021 14:48
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Quoting: paulz an electrician as sitting there hooking up wires. More like getting the wire in place
The licensed electrician may get the easier part of the jobs after he completes his apprenticeship. 
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Brettny
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# Posted: 29 Dec 2021 14:50
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You can use romex or UF(the gray coated stuff) in conduit to protect it, in this case you are useing it correctly. No need for THHN here.
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Nobadays
Member
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# Posted: 29 Dec 2021 14:59
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Having not long ago "tried" pulling 2 x #8 then through a 3/4" conduit that already had 3 x #10 then, I would highly suggest going with 1" od better yet 1 1/4" conduit. We had to pull all the wires out and then pull them all back through together.... and that wasn't easy!
Would it be possible to start with your conduit right at the load center? There are fittings for attaching the conduit directly to box. Would make a clean install.
As ICC points out, conduit capacity charts, unless noted somewhere, are based on single conductors not romex/direct burial UF-B.
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spencerin
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# Posted: 29 Dec 2021 15:11
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I think larger conduit is likely the best solution for me here.
Can THWN be exposed to air and water, outside of conduit but NOT in ground? The sections of wire that will be exposed to air and water will be protected inside a rigid enclosed space, sort of a massive conduit itself. I'm thinking this could be an avenue to allow me to run more wires in conduit.....
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Brettny
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# Posted: 29 Dec 2021 15:27
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Quoting: spencerin Can THWN be exposed to air and water, outside of conduit but NOT in ground? The sections of wire that will be exposed to air and water will be protected inside
All of the THHN would need to be in conduit. You cant surface mount that stuff like romex.
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gcrank1
Member
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# Posted: 29 Dec 2021 15:50
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I think you have opened a bag o' snakes 
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ICC
Member
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# Posted: 29 Dec 2021 16:01 - Edited by: ICC
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Quoting: Brettny You can use romex or UF(the gray coated stuff) in conduit to protect it, in this case you are useing it correctly. No need for THHN here.
Yes but thhn/thwn is so much easier to pull. IMO.
But no, it can not be left exposed.
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ICC
Member
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# Posted: 29 Dec 2021 16:03 - Edited by: ICC
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But then romex ( real name for code purposes = type NM) is not meant to be left exposed either. Neither is UF-B, IIRC. There are some exceptions such as if UF is hung high between buildings, I think. But where physical damage could happen from everyday life then wires need to be armoured or enclosed, behind a wall.....
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spencerin
Member
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# Posted: 29 Dec 2021 18:16
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Nah, I think the lid has been kept on the can. I needed some clarification and this has helped immensely.
ICC, so, UF-B can be direct-buried (at the proper depth) but needs to be in conduit when not?
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ICC
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# Posted: 29 Dec 2021 20:47
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Going by memory UF-B can be buried and that must be a 24" minimum. As well it can be run in conduit. It needs conduit physical protection above ground and down to the burial depth. UF-B is resistant to UV and water but requires physical protection when not buried to code depth. Inside a building, it needs to be in walls or protected from physical damage.
That is memory talking, but in this case, I believe the above is all accurate.
Where I am uncertain is the mention I made of UF-B overhead. That used to be okay when the UF-B was strung with a steel messenger wire (anchor) and was located some minimum height above ground level and driveways. Almost everybody does UG for everything they can these days, and that is better in many ways.
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Nate R
Member
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# Posted: 30 Dec 2021 07:52
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12" is fine for a gfi protected 15 or 20A circuit as you stated. This is the exception to the 24" rule.
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ICC
Member
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# Posted: 30 Dec 2021 10:31
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Quoting: Nate R 12" is fine for a gfi protected 15 or 20A circuit as you stated. This is the exception to the 24" rule.
So right! There are exceptions to so many things in the NEC
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spencerin
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# Posted: 4 Jan 2022 23:19 - Edited by: spencerin
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Another question -
I'm considering going with the 12" deep, direct-burial with GFCI breaker option. Code requires only what's above ground to 12" below ground to be in conduit in this case, which means the open end of the conduit is subject to moisture and debris infiltration.
Just humor me here - is there anything code-approved that can be fitted to/over the open end to obviously allow the wire to exit yet keep it watertight?
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ICC
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# Posted: 5 Jan 2022 10:15 - Edited by: ICC
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Quoting: spencerin which means the open end of the conduit is subject to moisture and debris infiltration.
Conduit is considered a wet location. I look at the transition from conduit to no conduit as being a drain, a place for water to exit if/when it intrudes into the conduit above that point. We use wire that is rated for wet location and all should be okay. But???
That said, if one is determined to try to make a water tight connection there are some fitting that might help. These are meant for use in solar wiring installations for use with the wires used for MC4 cables. The fitting fits a std box knockout. You should be able to fit one to a conduit end with an appropriate fitting. Here is a datasheet link . The images are of some I have in use on a trailer.
I do not know if they are NEC approved, so I guess this does not actually answer the question. . I do see them used on solar
They are referred to as strain reliefs, so maybe they don't count for those end of conduit sealing?
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gcrank1
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# Posted: 5 Jan 2022 12:43
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Silicone Seal the down/open end around the wires?
Or, dump a small bucket of round 'river rock' (no sharp edges) in the trench where the wire becomes exposed to provide some drainage IF water were to get in the top?
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spencerin
Member
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# Posted: 7 Jan 2022 17:23
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Another question -
How do I connect flexible PVC conduit to a conduit body where the conduit body nipple doesn't have female threads? I know they make flexible-to-rigid connectors, but those have male threads, which make them better suited for transitions to rigid PVC conduit or junction/pull boxes.
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ICC
Member
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# Posted: 7 Jan 2022 17:45
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Quoting: spencerin where the conduit body nipple doesn't have female threads?
The box is made with a female slip (and glue) hole or socket? Not sure I follow.... picture or link?
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