Running wire under the sink for an outlet


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Old 05-02-21, 08:03 AM
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Lightbulb Running wire under the sink for an outlet

Hi, I live in Southern California.
I am adding an outlet for my mother in law because she wants to buy one of those toilet bidets (that washes your butt).

When I remodel the house last year, my contractor did this for my bathroom (we forgot to tell him before he built the counter, otherwise the wire would be in-wall).

My question is if it is up to code. I got different opinions after searching online:
1. It is ok because wire would not be subject to physical damage.
2. I should use Liquidtight Flexible PVC Non-Metallic conduit like this one (or the one with 12/2 wire pre-assembled)
1/2 in. Dia x 25 ft. - Flexible PVC Non Metallic UL Liquid Tight Electrical Conduit

3. I should use Flexible steel conduit ( or the one with wire pre-assembled)
1/2 x 25 Flexible Steel Conduit

Option 1 is easy, just fish the wire out of the wall and staple it along the edge of counter.
Option 2:
Question 1: I cannot find an old work plastic box with 1/2 knockout unless I cut one myself. However, to think about it, if they don't make one, does that mean it is not supposed to be connected to a conduit.

Question 2: How would I feed the wire into the wall to the existing GFCI outlet.
1. Do I use a romex to connect to the outlet, and strip the romex sleeve after it exists out of the wall, and put it into the conduit? If so, how do I fasten the flex pvc conduit end to the wall?
2. If I feed the entire conduit into the wall, it would require me to open up a much bigger opening. How would I fasten the conduit to the 1 gang new work box, since it doesn't have 1/2 inch knock-out hole.
Opinion 3:
If I went with the Flexible Steel Conduit. The newly added outlet must be in a metal gang box, right?
I found this old work metal box that clamps on the cutout hole.
2-1/2 in. Deep Gangable Switch Box with NMSC Clamps and TIGERGRIP for Old Work
That takes care of one end of the cable, but it faces the same problem on the GFCI outlet end.
1. If I strip romex cable at the exit of the wall, how do I fasten the metal conduit to the wall?
2. If I feed the metal conduit into the GFCI outlet, how do I fasten it to the plastic gangbox?
Any suggestion is greatly appreciated.Thank you.













My mother in law apartment



My house - 14/2 romex

My house - 1 gang box

my house - result
 

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05-04-21, 04:57 PM
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--You don't put romex cable inside conduit.
.Why not? The NEC does not prohibit NM cable from being installed in conduit. It isn't normally considered good practice, but it is not prohibited.

1. I went to home depot, the senior electrical guy says it's fine to directly put romex in conduit without sleeving. When I asked about heat dissipation, he said it is fine for 15A which I seriously doubt it.
Huh! Put romex in conduit without sleeving? The conduit is the sleeving! I suspect the senior electrical guy meant "without the sheathing" and that just proves why you should be very very careful getting advice from the big box store guys. You might occasionally find a good one, but it is very rare. You don't strip the sheathing from NM cable before installing it in conduit.

2. Another popular belief is to sleeve the romex then put it into the conduit.
If this is so popular, please explain how you sleeve romex before installing it in conduit.
 
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Old 05-02-21, 05:25 PM
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No has replied so I will take a shot, and may get qualified by others that reply.

You are ambitious with lots of questions, which is good. However my perspective is not being sure if your current knowledge base or skill level is enough to get you moving on this, or maybe you just need to narrow things down before you can get useful replies, rather than all the info in your post?

Meanwhile some pointers on workmanship and code, bear with, it is not clear what you are aware of.
--You do not attach metal conduit to a plastic box.
--You don't put romex cable inside conduit.
--There are specific connectors to attach flexible metal conduit to metal boxes.
--Most old work plastic boxes, don't have 1/2" knock outs, and simply accept romex via the captive
cutouts you see on each end.
--Romex should not be exposed inside cabinets.

For the pic that says mother in law apartment, you need a metal box that transitions romex from the outlet, to flex metal conduit at the start point inside the cabinet, then run the FMC inside the cabinet to a metal bidet outlet box.

Finally keep in mind that the devil is in the details with electrical work. This includes details that one is not aware of. May I suggest figuring out what can go wrong in advance and making sure that doesn't happen.

Even if you are certain what device or material goes where, an error in workmanship, and there are many ways an error can occur, can spell failure.
To name a couple...
--A wire gets nicked during stripping, then breaks at a connection point as a result.
--A metal conduit termination that doesn't protect conductors and causes a short to ground.
 
Norm201 voted this post useful.

Last edited by Gen; 05-02-21 at 06:01 PM.
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Old 05-02-21, 09:57 PM
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@Gen, thank you for your information. I understand I wrote quite a bit. I am not a electrical professional by any means. I have replaced outlet with smart outlet, replaced 3 ways light switches, and replaced breakers, installed ceiling fan. I can measure typical 3 wires by multimeter.​ So this is my knowledge base.

--You do not attach metal conduit to a plastic box.
Yes, I understand with metal box, you can use either pvc or metal conduit, but with plastic box, only plastic conduit. Hence, option 2, plastic box with flex pvc conduit. And option 3, metal box with flex metal.


--You don't put romex cable inside conduit.
Yeah, about that ... I have heard all kinds of sayings:
1. I went to home depot, the senior electrical guy says it's fine to directly put romex in conduit without sleeving. When I asked about heat dissipation, he said it is fine for 15A which I seriously doubt it.
2. Another popular belief is to sleeve the romex then put it into the conduit. Since you can put individual THHN in the conduit and romex's inner insulation is rated the same with THHN, this you can put sleeved romex in conduit. Personally, I'm more leaning towards this. The reason I mentioned this method because I can connect the GFCI outlet end with normal romex cable through the plastic gang box clip.


--There are specific connectors to attach flexible metal conduit to metal boxes.
yes, I saw at home depot, it sells 8 ft flex steel with 12/2 wires in it and adaptor. It is the push in kinda adaptor.



--Most old work plastic boxes, don't have 1/2" knock outs, and simply accept romex via the cutout.
yes, I see old work 2 gang with knockout, but never with 1gang.

--Romex should not be exposed inside cabinets
Agreed, another popular belief on the internet is that if the the romex is securely stapled at somewhere not be the subject of damage, then it is ok. I was worry about the faucet rubber o-ring eventually give out and start dripping water down. Hence, I thought about using liquid tight pvc conduit.


 
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Old 05-02-21, 11:45 PM
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@Gen
Just to make sure I understand correctly. As soon as the romex exists out of the wall, I should clamp the romex to a junction box, and then out of junction box to metal outlet.

How come we use FMC not LFMC since it could be wet area if water drips?
 
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Old 05-03-21, 05:05 AM
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Why bother with any electrical system at all? I'm assuming you're going with an instant hot water module.
I have installed several bidets and am not a fan of the warm or hot water system (cold water is fine and one gets use to it very quickly). However in your setup, where the sink and toilet are on the same wall, you do not need an electrical system. Just tap off the hot water sink line and pipe to the bidets (the add-on type that you attach to an existing seat have both a hot and cold water option). If the water needs to run for short period of time to flush out any standing cold water in the hot water tubing, just switch the system to clean until it gets warm.
 
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Old 05-04-21, 10:10 AM
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I don't see any code issue with the way it's wired. The location of the cable protects it from damage as no one is going to stack things up to the countertop under the sink. Of course, this is an opinion statement - and your local inspector (AHJ) might have a different opinion.

AFAIK, there's no issue with a plastic box in the location you have it. Not all that common of course, but again, not a code violation as far as I know.

If you needed to protect the cable, you could sleeve the NM-B cable in 1/2" PVC or EMT conduit (I would use PVC). It wouldn't actually connect to anything, just terminate just outside the plastic box. The plastic box would continue to have the cable clamp as-is. There's no issue with sleeving cable in conduit - as it's just protecting the cable, not acting as a raceway.

If you wanted to upgrade the box, you could use a double gang metal box. It would be a bit more complicated to mount as you'd need to add a 2x4 or something to screw it to. You could then attach a conduit directly to it. Then on the wall-end of the conduit, use a EMT-to-Romex connector, which acts as a clamp for the cable entering the conduit system.

Number of different options... not sure that any are really fully worthwhile though!
 
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Old 05-04-21, 04:57 PM
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--You don't put romex cable inside conduit.
.Why not? The NEC does not prohibit NM cable from being installed in conduit. It isn't normally considered good practice, but it is not prohibited.

1. I went to home depot, the senior electrical guy says it's fine to directly put romex in conduit without sleeving. When I asked about heat dissipation, he said it is fine for 15A which I seriously doubt it.
Huh! Put romex in conduit without sleeving? The conduit is the sleeving! I suspect the senior electrical guy meant "without the sheathing" and that just proves why you should be very very careful getting advice from the big box store guys. You might occasionally find a good one, but it is very rare. You don't strip the sheathing from NM cable before installing it in conduit.

2. Another popular belief is to sleeve the romex then put it into the conduit.
If this is so popular, please explain how you sleeve romex before installing it in conduit.
 
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Old 05-04-21, 06:57 PM
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Huh! Put romex in conduit without sleeving? The conduit is the sleeving! I suspect the senior electrical guy meant "without the sheathing" and that just proves why you should be very very careful getting advice from the big box store guys. You might occasionally find a good one, but it is very rare.
You are absolutely right, English is my second language. I have been in US for more than 10 years, I still get confused from time to time. I am pretty sure he meant "sheathing". When I say "sleeve", I mean strip the romex outter layer.
 
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Old 05-05-21, 10:47 PM
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I have come up with a plan.
1. Cut a hole at the opposite wall
2. Fish Romex to the hole below the counter
3. Install a handy box right next to the hole
4. Install a wire clamp on the box
5. Mount PVC with THHN or Romex to handy box
6. Mount the other end to a metal box with a side clamp to clamp on the cutout.
7. Install a weatherproof box over the metal box because I am worried the sink water will overflow and get in the outlet (e.g. accidentally knock off a cup of water)

Any suggestions?

diagram
 
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Old 05-07-21, 06:39 PM
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Just to be a little neater...If feasible I would install the handy box over the hole( to cover it) rather than next to it. (Or consider using a 4" square box) Then use the knockout in the back of the box for connections.
 
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Old 05-08-21, 04:02 AM
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From what I see in the pictures I would say you are fine. The Romex is not subject to physical damage the way you have it run and should not need protection.

However, it appears that you have run 14/2. Make sure that the existing wiring is the same and the breaker protecting the circuit is 15 amps. If it is 20 amps and/or the existing wiring is 12/2 then the new wiring needs to also be 12/2.
 
 

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