nm in metal conduit on a rewire

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Old 05-03-07, 07:57 AM
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nm in metal conduit on a rewire

Is it an acceptable practice code to run NM wire through metal conduit, (taking capacity issues into consideration), provided I ground each metal box with the ground wire in the NM? What would the appropriate type of securing nut in the box be?
Any information would be appreciated.
 
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Old 05-03-07, 08:57 AM
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Based on what Iíve read here, itís best not to run NM cable through conduit due to heat issues unless it is a short length for protection, say from a box on a basement wall up to the joists where the NM would then run exposed.

Where you are using a complete conduit run from box to box you should run individual wires (type THHN/THWN).

If you describe your project in more detail, the pros here will give you more specific advice.
 
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Old 05-03-07, 09:27 AM
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If you have existing conduit, or if conduit is required where you are, then run THHN wires inside. It will be shorter and easier. If you wish to use conduit for protection of NM cable, then use it only where needed.
 
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Old 05-03-07, 09:42 AM
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It's allowed but not preferred. There's usually a better way.
 
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Old 05-03-07, 11:51 AM
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Thanks to all who replied so quickly...

I didn't give the details on what I was looking to do, because, initially, I wasn't sure if the electrical inspector would allow it, anway. I was waiting on a call back from him when I posted here.

My sister owns a house with metal conduit, and individual cloth covered wires running through them. (I believe the house was built in the 50's.) Through the years of her ex-husband and sons jury-rigging everything under the sun, she now has, what I consider an accident waiting to happen. I built an addition on my own house, and had everything inspected, so I have SOME wiring knowledge...just not enough to attempt this without something of this nature without first asking a whole bunch of questions.

My suggestion to her is to rewire each circuit, (it's a small house with an unfinished basement), total 12 circuits, not including the AC and furnace, which were installed recently, so the wiring should be up to code. By utilizing the existing conduit, it would alleviate the busting up of plaster walls to run new wire. I would like to use NM, just because I have experience with it. She had a new service panel installed last year, so by running NM back to the panel, I should also be able to resolve the ground issue, as the existing outlets are 2 prong, except where 3 prongs were installed incorrectly.

By the way, the inspector called back, and said it would be fine to run through the conduit, provided I grounded correctly, to each box.
 
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Old 05-03-07, 12:02 PM
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It's much, much, much easier to pull individual wires through the conduit than NM. But if you can get it through without damage and without violating fill rules, then you can. I still wouldn't, however.

I know you have experience with NM. But really, how long would it take before you had experience with THHN too?
 
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Old 05-03-07, 12:06 PM
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Disclaimer: You are taking a great liability upon yourself doing this for someone else since you are not licensed. Even if it is your sister you are, in my opinion, making a mistake. Tread very carefully.

You will find it easier and cheaper to use THHN.

Also, you MUST correct any wiring that is not up to present day code. That means new receptacles if the existing ones are not properly spaced. That means AFCI breakers for the bedrooms. That means GFCI protection in the kitchen, bathrooms, unfinished basement, garage and outside. That means the bathroom circuits must be proper, as well as the small appliance circuits (kitchen, dining room, pantry).

Bottom line you probably cannot just replace the existing wiring without making other changes.
 
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Old 05-03-07, 12:23 PM
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Thanks again to the moderators for their input. The inspector said it would be ok for me to help, as long as she did the work. As far as code violations, that would be where the inspector comes in, correct? My goal here is get her house safe, as well as compliant.
 
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Old 05-03-07, 12:44 PM
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Inspections are good and essential, but don't rely on them to guarantee safety. If the inspector is in and out in ten minutes, he's not going to catch everything. Most of safety and good workmanship is still up to you. If you're not sure how to do something correctly, then don't do it until you are sure.
 
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Old 05-03-07, 12:51 PM
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Helping your sister is one thing. Doing it for her is another. The line between those two can be drawn just about anywhere. That is why I said to tread lightly.

As John stated, the inspection might not catch everything. Further, when it does catch something, you do not want to have to undo hours of work to correct a simple mistake that could have been avoided.

It is up to your sister to do the job properly from the beginning, and that means knowing that bathroom receptacles cannot share the same circuit as bedroom receptacles, for example, and that you need at least two circuits serving the kitchen counter, and that no lights can be on that circuit. There are plenty of other rules I eluded to as well. You and your sister need to learn them BEFORE you start the job.
 
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Old 05-08-07, 07:22 AM
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After doing more research on the subject and following the advice given here by the moderators, I have concluded that THHN would be the way to go where the existing conduits can be reused. Due to some of the conduit runs being incomplete, (sections of conduit are missing), I will need to run some NM.
That leads me to the next question/problem. When verifying the main panel, (which was installed last year), was grounded, (remember, we're going from a 2 wire system without ground to a 2 wire with ground), I found that there may be a problem with that...It appears there are 2 ground wires running to the main ground bar...One is a braided copper wire that comes in from the utility pole, and the other is an aluminum wire that runs to a copper water line. The problem, (I think), is the wire is attatched about 25 feet from where the main comes into the house. Shouldn't this be within 5 feet, plus be on the street side of the meter?
Also, regarding THHN...I've read that some professionals will strip the exterior sheathing off NM wire to utilize the wires inside like THHN. Is this acceptable? Would the bare ground wire be ok to run in metal conduit?
Thanks again for your help.
 
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Old 05-08-07, 07:39 AM
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Yes, it should be within 5 feet by modern code. But there's lots of things about your installation that don't meet modern code.

No, it is not acceptable to strip NM sheathing to use the wires inside. Besides, it's a lot of work.

Yes, you can run a bare ground inside conduit.
 
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Old 05-08-07, 07:53 AM
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There must be a jumper to go around the meter. The jumper ensures that the street side of the water pipe is electrically connected to (or bonded to) the house side.
 
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Old 05-08-07, 01:53 PM
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Could you describe exactly what sort of conduit the current wire is in?

By the 'bare ground in conduit' question, I presume that you are asking about the equipment ground wire for your branch circuits. But if you are asking about the 'grounding electrode conductor' running from your service to your water pipe, there is another issue to keep in mind: the wire could be bare or insulated, but is must be 'bonded' to _both_ ends of any conduit used.

-Jon
 
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Old 05-09-07, 09:30 AM
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winnie,
You are correct...I am referring to the branch circuits in conduit. Ground wire to the water main is run bare through open floor joists in unfinished basement.
 
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Old 05-09-07, 12:20 PM
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Upon further investigation, it turns out the water meter is actually outside the house. There is a shut-off valve, only, at the point where the water line enters the house. Does this validate the connection to the copper water line, or is the requirement still there to be 5' from entry to house?
 
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