Travelers in separate conduit?

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Hello Don

I was just getting ready to ask if maybe you all knew something I didn't,
like maybe it was in Canada.

Anyway I found this I knew it was a violation and had to find it.

NEC_300.20(A).jpg


Thanks: Don

Ronald :)
 
Hello Gus and Don

Like I said I agree with you usually there is no harm and the heating isn't that great.

But it is a against the code and that is for a reason.

I look at it like this if we didn't have that code everyone would be abusing it.

We have rule and measures for reasons like you can't parallel any conductor smaller than a 4/0.

If they didn't have that rule starting at that larger size you would see electricians every where
paralleling 2 # 14/ 2 nm romex for water heaters, 2 10/3 nm romex for ranges and the like every where.

Tom no it doesn't have a thing to do with magnetic fields, what ever give you that idea?

Ronald :)
 
ronaldrc said:
My Bad, I knew that didn't sound right and didn't look it up.:D

Thanks :)
Click to expand...

I just assumed it was a typo. Some use the 10-key pad instead of the top row on the keyboard, and I just figured you accidently moved your finger up one key from the '1' to the '4'.
 
Jim told me about this thread tonight, I just read it over and I think he's onto something here...

raider1 said:
Take a look at 300.3(B).

Chris
Click to expand...
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
Click to expand...
I can read that as saying that "if I am not using the grounded conductor, then I need not install it in the conduit."

How can the sentence not be read that way?

------
Bear in mind, Jim and I know that there will be current induced on the conduit - I'm looking at what appears to be a hole in the language.
 
Ronald,
After a bit of research, it appears that I am wrong about the Canadian code rule. The rule in their code covers what is 300.20(B) in the NEC, not 300.20(A) like I thought.
 
Lets settle this

Lets settle this

Thank you for your posts so far, but I get the feeling we are not settling the issue. We have established that it is a code violation but, I still have several local inspectors that are not convinced that this is a safety issue. I teach "Electrical Level 2A" at Gateway Community college in Phoenix, I am going to settle this the way we do in class. I will build a model this weekend and test with various loads connected. I will then be able to predict how strong the magnetic fields will get, and how much inductive heating will occur under most conditions. I should also be able to predict when the overcurrent protection will be adversly affected by the added impedance. I will post the results when I have them. Anyone else that wants to do this, Please share your results as well. Maybe I will learn something new or, maybe we can start to eliminate what I feel is a dangerous practice.
 
ronaldrc said:
Hello Gus and Don


....Tom no it doesn't have a thing to do with magnetic fields, what ever give you that idea?

Ronald :)
Click to expand...

Because if I clamp an amp meter around a conduit that has only travelers in it, I will have net current indicated. Net current means a magnetic field. I need either the return switch leg or the neutral in the conduit to cancel this field. Refer back to 480s explanation of a single pole sw leg.
 
George,

George Stolz said:
I can read that as saying that "if I am not using the grounded conductor, then I need not install it in the conduit."
... - I'm looking at what appears to be a hole in the language.
Click to expand...

I agree.
I think that is a 'hole' in the language, which may miss the 'Intent' of NEC.
The physics seem clear enough, but the wording of rules is difficult.

Comments?
 
Single phase, 2-pole circuits may not need a Grounded conductor. This is an example that conforms to the wording in the first sentence of 300.3(B).

If one is supplying lighting with 3-way or 4-way switching, how is it that the travelers can be installed without the conductor (most likely the switched conductor) in the same raceway without, 1. violating 300.3(B), and 2. possibly setting up a heating condition within the metallic raceway.

Ronald also brought up a valid concern, of the circuit not being able to handle a ground fault condition properly if the impedance is substantial enough.
 
Pierre,

I agree that a two pole circuit may not require a neutral.
OTOH, a switch loop and two returning switch legs would balance current flow.
I am trying now to imagine a 3-way circuit where there would be NO balancing current flow.
Oh, yeh, the infamous 'California 3-way' (which is not code any more).

Just to show how friendly these comments are meant to be,
let me remind you of the old country 3-way made with several strings
tied between a pull-chain fixture and each door-jamb. My grand-daddy's favorite!
Of course, there was no return wiring there, ha.

To be more serious, though:
From my calculations, which I did for my boss after a similiar comment,
the difference between D.C. resistance and 60Hz A.C. Impedance
is about .017 percent.
That makes me think that impedance is not an issue.

I have heard your comment before, but still don't understand where it would apply.
In a Radio frequency circuit, I would buy it in a New York Minute.

Your comments always catch my ear. Try me.
 
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