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Old 06-19-02, 02:05 PM
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conduit

I am running 4 cabels of 12/2 wire with ground through 1 1/4 inch coduit for 50 feet from main panel to 4 circuits . The wire is romex and taped together in the conduit. Is this ok? Thank you
 
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Old 06-19-02, 08:36 PM
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Romex is UL approved to be used without conduit. It's doubtful 4 of them in any conduit is legal because UL most likely hasn't tested it for that application. Why don't you use THHN wire since your running conduit?
 
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Old 06-19-02, 09:00 PM
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12/2 cable is calculated as if it was round cable 1/2" in diameter. Thus each cable is considered to to have a cross-sectional area of 0.196 square inches. Four such cables will then have a total cross-sectional area of 0.785 square inches. For four cables, you are limited to using 40% of the cross-sectional area of the conduit. Thus, you need a conduit with a cross-sectional area of at least 1.96 square inches.

Different kinds of 1.25" conduit have different cross-sectional areas. Since you didn't say what kind of conduit, I'll need to make an assumption. Let me suppose you meant EMT conduit. 1.25" EMT conduit has a cross sectional area of 1.496 square inches. So you can see that this is not big enough to satisfy code. There are 12 other types of conduit listed in the code, but none of them are the required 1.96 square inches in the 1.25" size.

Whenever you put multiple wires in the same conduit, you must also consider the potential ampacity reduction required. Your four cables will still allow you to use a 20-amp breaker, but if you put any more in the same conduit, you will be required to reduce the breaker to 15-amps, even though it is 12-gauge wire.
 
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Old 06-20-02, 04:53 PM
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conduit

The conduit is made of pvc 1-1/4 inch round with 4 elbows. Of the 4 cables that are in the conduit only 3 are being used I can do without the 4th one but it will have to stay in the conduit because it is taped to the other wires. Is this ok? Thank you for the help.
 
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Old 06-20-02, 05:37 PM
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If your installation will be inspected by the local municpality, it probably would not be acceptable. The inspector would assume that at some point the fourth cable would be used for something.
It sounds like these cables are taped together for a significant legnth. You will have a lot of trouble physically pulling these cables through the conduit without breaking the cable or the PVC conduit at the elbows.
Could you use individual conductors and at either end of the conduit but a junction box to convert to romex?
 
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Old 06-20-02, 06:07 PM
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conduit

The wire in the conduit is romex 12/2 with ground there are 4 cables going through. AT one end 2 of the cables go into one junction box and the other cable goes into another. At the other end the cables go into the main panel box with 3 different breakers, one being a gfi for a tub.
 
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Old 06-20-02, 07:45 PM
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The codes for conduit fill do not care at all whether the wires are carrying current or not. Ampacity calculations care, but conduit fill calculations do not.

I'm not sure it was a really good idea to tape the cables together.

Strangely enough, saying that the conduit is "PVC" is still not specific enough. The code covers several kinds of PVC: Rigid PVC schedule 80, rigid PVC schedule 40, HDPT, type A rigid PVC, and type EB PVC. But anyway, as I said before, all of them are too small.

Before going to the trouble to remove the extra cable, call your inspector and discuss the situation.
 
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Old 06-21-02, 02:46 PM
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conduit

I gess this comes down to is this a dangerous situation or not.My concern is if this will start a fire or whatever. The 3 circuits won't be using much juice one circuit goes to a jucuzzi one goes to a gfi plug that feeds a switch for an exhaust fan and the other goes to a gfi plug that feeds a switch for a light. The 4th cable was put in the conduit just to have on hand. These cables are for two bathrooms. Please reply. Thank You,
 
  #9  
Old 06-21-02, 02:49 PM
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Romex in conduit?

I'm confused as to why Romex is being ran in conduit. Never heard of such a thing.
 
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Old 06-21-02, 05:05 PM
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John's calculations are correct. PVC conduit sch 40 nor sch 80 has enough capacity to carry the four romex cables. PVC sch 40 has 1.4 and sch 80 PVC has 1.2 and you need 1.96.

As for the ampacity derating you have 4 cables and as far as I can pick up three of the four cables are 120 volt rated making the black and white wires both current carrying conductors. YOu therefor have a total of 6 current carrying conductors not counting the spare romex cable. This means that you must reduce the ampacity of 20 amp rated branch circuits being 12 awg conductors down to a 15 amp breaker because of the 20% reduction required for 4 to 6 current carrying conductors. If you energize the fourth cable you would have an ampacity less than 15 amps and unable to use those cables at all for 120 volt wiring.

YOu ask if this is safe. What you discribe does not meet the minimum safety standards therefor it would not be considered as safe.

YOu could solve your coduit fill problem by doing what was previously suggested by changing the romex in that junction box at the end of hte conduit from romex to THHN and running those conductors to from that junction box to the panel as single THHN conductors but switching back to Romex in the junction box at the other end.

However the NEC still requires you to protect those 12 awg conductors to 15 amp breakers and you no longer can use the conductors you installed for the bathroom receptacle becuase the bathroom receptacle must be served by a 20 amp branch circuit. Even though you have 12 awg conductors this branch circuit is considered as a 15 amp branch circuit becuase the branch circuit amp rating is rated by the overcurrent device being the breaker serving that conductor that is now 15 amp rated due to more than three conductors in a raceway.

A suggestion to solve your design problem is to run two 3/4" or 1" PVC conduits and install two romex cables in each conduit. Then you would be fine without concern of conduit fill or ampacity reduction requirements.

HOpe this helps

Wg
 
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Old 06-21-02, 05:57 PM
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Wg, I think you overlooked the fact that that ampacity derating is from the 90-degree ampacity of 12-gauge wire. So you should derate it from 30 amps, not from 20 amps So you can continue to use a 20-amp breaker until you add your tenth conductor to the same conduit (i.e., the fifth 12/2).

Your idea of adding a second conduit is probably the best solution to the conduit fill problem.
 
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Old 06-21-02, 06:11 PM
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John you did it to me again. You caught me at the exact same mistake the last time this subject came up. As usual you are accurate in your statement allowing the 20 amp breaker till you energize the 10 th conductor is accurate. I made the same blunder as I did the last time we had this discussion. Maybe I will learn one day.

Wg
 
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Old 06-21-02, 07:16 PM
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confused

The reason for the conduit was , because there were wires running along the walls in the garage which I thought would be out of code and I wanted to do it neatly. I thought puting the wire in the coduit would be neat and within code. I gess I was wrong. I am a little confused about changing the wire in the junction box to thhn what is thhn? and the only junction boxes I have are the two at the end of the conduit which are not connected to the conduit . The wires run out of the conduit for about a foot and go into the two junction boxes which have romex wire going into them for my curcuits. And on the other end there are no junction boxes the wire comes out of the conduit for about 3 feet then goes into the main panel. Thank You
 
  #14  
Old 06-21-02, 09:24 PM
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YOu can extend the conduit and connect both ends to the junction box and panel by using the same type conduit or installing a piece of flexible conduit using terminal adapters on the end of hte PVC conduit then a coupling then a flex connector converting that conduit to a flexible conduit. If you use THHN then that THHN must be protected in a conduit.

THHN is single strand wires just like the black and white wires you found inside your Romex only single strands without the outer sheath of the Romex. That is why the THHN is required to be protected by conduit becuase those wires are without the outer sheath of your Romex.

Hope this helps

Wg
 
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Old 06-22-02, 06:24 AM
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Interesting, based on everything I've read here, joe4h is using the "conduit" as a wire chase to neaten up the installation - hence the reference that the "conduit" is not attached to the junction boxes. How does the code look at this? I ask this question because when my house was built, I installed several pieces of CPVC pipe (not conduit) between the basement and the attic for future use - to make it easier to pull wires. So far, I've only used a couple for Cable vision and phone>
 
  #16  
Old 06-22-02, 09:24 AM
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Complete system

There's a note to table 1 in chapter 9 that I've never fully understood:

"(2) Table 1 applies only to complete conduit or tubing systems and is not intended to apply to sections of conduit or tubing used to protect exposed wiring from physical damage."

I can find no definition of "complete conduit or tubing system," and I have no way to figure out what "complete" means. How long does a piece of conduit have to be before it is a "complete system"?

Even if you decide that the system is not "complete," does that mean that you can cram as many wires in there as you can?
 
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Old 06-22-02, 11:05 AM
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John I believe DaveF has a point. This post pertains to a long piece of conduit that is not connected to anything. This throws a curve to the rules if Note 2 applies omitting the requirements of 40% fill for more than two cunductors in a raceway.

In this case we have a perdominant nonmetallic wiring method using conduit only to sleeve for protection. I would read the the conduit fill calculation you and I were discussing were using 100% fill not the 40% fill required in table 1 omitted in this setting by rule 2.

The conduit fill of a predominant Romex wiring style would still have to be calculated but not as a conduit system limiting the 40% fill for more than 2 conductors in a raceway omitted by rule 2 but would still have to be calculated using the 100% fill.

The numbers would change allowing more Romex cables in a conduit sleeve but the fill limit would still exist only not at 40% fill but 100% fill which would make quite a difference.

If we took 1 1/4" EMT as you originally calculated we would have a 100 % area square inch of 1.49. If you look at what you used for 1 1/4" conduit that 1.49 was what you used. Therefore Note 2 has been met by omitting Table 1 calling for 40% fill in your calculation. Your original calculation still stands becuase you did not use table 1 on your calculation as rule 2 dictates you not to use.

You originally calculated that situation correctly concerning conduit fill of Romex in a sleeve.

The ampacity deration is omitted only if that conduit was less than 24" long. The conduit in this post was much longer than that so the ampacity deration is still correct as you originally calculated also limiting to a maximum current carrying conductors of 9 current carrying conductors. The original post claimed 4 Romex cables in that conduit all being 120 volt rated therefor you have 8 current carrying conductors in that conduit omitting any reduction of breaker size to 15 amps as you originally spoke in your calculations.

Hope this rambling reply helps

Wg
 
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Old 06-22-02, 08:49 PM
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conduit

At this point I don't know what to do. I might pull everything apart and just run the romex along the wall. I gess what I need to know is what can happen if I leave the wire in the conduit. Also at this point I'm completely confused as what the codes realy say. I would appreciate all help on this situation.ThankYou, Joe 4h
 
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Old 06-22-02, 10:28 PM
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terrywouldbe
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Joe, I'm not an expert here, but I would just cut everything out and run the romex along the studs, securing them with staples every 2 - 4 feet.

Romex is approved for use without conduit, as Mike134 said.

Considering the amount of discussion here on this topic, and considering the technical level with which it is discussed, there may be something I'm missing.

I would think that NEC would require the conduit to be attached to the junction boxes - I'm unclear as to whether or not your current situation involves this.

Anyway, that is what I would want to do to just make it simpler. Of course, the Romex which runs into the knockouts of the (steel ?) junction boxes should be anchored to those boxes with Screw-In cable connectors, so as to not damage the cable.

This is just my unprofessional opinion, Joe, and you should probably not do anything with it until John or Wg replies.

If I'm wrong about this, I hope someone will enlighten me; but it seem as though the discussion is a bit deeper than what Joe is needing

-Terry
 
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Old 06-23-02, 08:26 AM
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NM cable is allowed in most areas without conduit, but only where protected from physical damage. In most cases, stapled to the surface of studs is not allowed because it does not provide adequate physical protection. Through bored holes in the studs would probably be allowed.

However, I still cannot give you a definitive ruling on whether note (2) of Table 1 of Chapter 9 saves you or not. Seems that you could advance the argument that almost any installation was not a "complete" conduit system, thus remdering all of Chapter 9 meaningless except in Chicago. This doesn't seem logical.

Again, I appeal to the experts. Has anybody seen a reliable definition of "complete conduit system" from an authoritative source?
 
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Old 06-23-02, 06:05 PM
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conduit

What I would like to know is what would happen if I left everything as is, and would it help the situation if I could take one of the cables out of the conduit.
 
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Old 06-23-02, 09:35 PM
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joe4h, sorry about the technical jargon in this post. I got a bit difficult to provide you with an accurate answer. As far as I can see you would be fine if you split the Romex cables into two conduits or increased the size of your conduit one or two sizes bigger in diameter than you have now. YOu are exceeding the conduit fill calculation per appendix C for all conduits types. No concern is needed for ampacity deration per table 310.15.B.2.A.

You ask what can happen. YOu are creating a condition that is too tight for that conduit per the NEC which can damage the wires being pulled into the conduit causing shorts or packing so tight that the conductors can not cool properly.

John the following copied section of hte NEC 2002 and the handbook commentary, sorry that is all I know to provide for substantiation as to a complete conduit system available in the NEC. I suspect the best help would be the use of the Handbook commentary and explaination concerning complete conduit systems.

Chaper 9 Tables


Table 1 Percent of Cross Section of Conduit and Tubing for Conductors
Number of Conductors All Conductor Types
1 53
2 31
Over 2 40


Notes to Tables
(2) Table 1 applies only to complete conduit or tubing systems and is not intended to apply to sections of conduit or tubing used to protect exposed wiring from physical damage.

NEC Handbook Commentary;

The maximum fill requirements do not apply to short sections of conduit or tubing used for the physical protection of conductors and cables. Cables are commonly protected from physical damage by conduit or tubing sleeves sized to enable the cable to be passed through with relative ease without injuring or abrading the protective jacket of the cable. However, a fitting is required on the end(s) of the conduit or tubing to protect the conductors or cables from abrasion. [See 300.15(C).]

HOpe this helps

Wg
 
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Old 06-24-02, 06:35 AM
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Thanks Wg. It's a bit clearer, but still far from definitive. The NEC Handbook suggests that "short sections" of conduit are not "complete conduit systems". Now I just wish I knew how short is "short."

Something tells me that 50 feet is not "short," but maybe that's just me.
 
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Old 06-24-02, 12:40 PM
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In a discussion elsewhere, a gent who seems well qualified described "short sections of conduit" as those used to bridge a gap, for example through a return air duct or similar hazardous gap of a couple of feet or less. I agree that 50 feet is only short if your tractor has lost its brakes.
Tom Carter
 
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Old 06-24-02, 03:42 PM
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Tom, I liked that catchy last statement. Made my mind go graphic.

You could look at 50' of conduit as being short in comparison of the total footage of wiring in the entire project.

I don't know of any where in the NEC or elsewhere that specifically defines "short sections of conduit for protection or sleeving" I guess that definition should be ruled upon by the AHJ.

I see the concern of gray that John is implying.

Guess we just used accepted practice as to incomplete conduit for sleaving as being a building not predominantly wired in a condiut wiring style.

Wg
 
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Old 06-24-02, 05:54 PM
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conduit

Just to let you guys know , I took the conduit out and ran the cables along the wall , in the corner by the celing through the sheetrock in between the floor joist to the junction boxes.I am under the impression that as long as I keep the cables 8 feet up it's within code. What I would like to know is if I can double up the cables and use one cable staple for two cables.
 
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Old 06-24-02, 06:48 PM
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Not sure the NEC mentions anything about any "8 feet up" rule. But I do understand that some local juristictions enforce this rule. If the inspector thinks the cable is protected from physical damage, then it is. The code says that the cable must be protected "where necessary".

Yes, you can use one staple for two cables, assuming the staple is long enough so that it is in no danger of coming out. Lay the two cables flat, one on top of the other, before driving the staple. Flat cables must not be stapled on edge.
 
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