8-3 Romex in PVC conduit

Discussion in 'Electrical Forum discussion & Blog' started by dabiz7, Jun 13, 2008.

  1. dabiz7

    dabiz7 New Member

    Messages:
    42
    Trying to finish my kitchen re-model...I will be running a new run (25') of 8-3 Romex from panel in the garage to hole through wall into kitchen for the oven. The instructions say use 8 ga wire. My local electrical inspector guy told me that exposed wiring in the garage should be in conduit (PVC, metal, etc).

    BUT, I thought that I had read and heard that you aren't supposed to run Romex in PVC conduit. Something about the heat build-up. is this true or crap? I have 30' of Romex already bought, don't want to take it back. Do I strip the jacket off the Romex before fishing through the PVC or just forget about it and run it in the PVC as usual?

    what a great forum, I read the plumbing and electrical sections everyday !
  2. Furd

    Furd Engineer

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    446
    Location:
    Wet side of Washington State
    DO NOT strip the outer jacket from the cable.

    It is perfectly acceptable to run non-metallic sheathed cable through conduit for physical protection.
  3. Bob NH

    Bob NH In the Trades

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    Location:
    New Hampshire
    You are better off running THHN in the conduit. You will have enourmous difficulty pulling #8 Romex through conduit.

    You can put four #8 THHN through a 3/4" conduit and it will be rated at 50 Amps. The #8 Romex is rated at only 40 Amps.
  4. dabiz7

    dabiz7 New Member

    Messages:
    42
    Well, It hink you guys are right, after handling the 8-3 Romex for a little while, I think it will be about impossible to pull it through the 3/4 PVC conduit. But here is my problem, I already bought 30 ft of Romex, as expensive as copper wire is, I really don't want to go buy some TTHN. Why couldn't I just strip off the outer jacket of the Romex and then I would have four seperate wires, same as if I had bought THHN, right?

    Just trrying to save some cash!

    Why would seperate wires be rated higher than bundled together in Romex? Isn't the insulation used, the wire gauge the same between #8 wire in the Romex and seperate THHN wire?

    Thanks for the advice
  5. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    There you go, thinking logically. I'm not sure, but I think the reason you can't use the individual conductors is that they aren't individually marked with their specs. I'm sure someone who knows will give us the true poop.
  6. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Cable is listed for use as an assembly. Removing the outer jacket any further than just for connections will void that listing. Get some larger I.D. conduit.
  7. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    If you strip it and pull it through the conduit I doubt very much if the inspector will care. I would not tell him; I would just do it. There is no issue of safety.

    It will probably be apparent because the ground is probably not insulated.

    If you pull a piece of the jacket off and slip it over the end of the wires and into the end of the conduit it may look like you pulled the Romex, but it could also give it away.
  8. Chris75

    Chris75 Electrician

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    Location:
    Litchfield, CT
    I guess there is always the conscience thing though...:rolleyes:
  9. dabiz7

    dabiz7 New Member

    Messages:
    42
    Here is my compromise !

    Strip off the jacket, use the black, white and red wire, and go buy 30ft of green wire to replace the un-insulated ground in the Romex. hahahaha

    I think I like this option best.
  10. kd

    kd New Member

    Messages:
    207
    Measure the outer diameter of the cable. Use Pi R squared to compute the area. If it is larger than .269 sq inches you cannot run 8-3wGn cable in 3/4 PVC 40 conduit. This is based on 53% fill. If size is OK put busings on each end, lube it, and pull it through. If not, install bigger conduit. If you must use the 3/4 PVC--install a box to transition from cable to conduit. Then strip off the sheathing. You do not need to do splices. You can run 5 #8 THHN in 3/4 PVC, so 3 plus ground should be easy to pull. It is OK to use the bare ground wire.
  11. jimbo

    jimbo Plumber

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    8,997
    Location:
    San Diego
    Just curious.....are the conductors in a Romex cable actually THHN, just not marked, or is it the case that they are not actually rated??
  12. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT

    Not sure because they are actually not marked, most people believe they are THHN.
  13. mc_1_2_3

    mc_1_2_3 New Member

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    Location:
    Western Pennsylvania
    Wire in Romex is solid, THHN is stranded, much easier to pull the THHN. The insulation is single layered on the wires in Romex, THHN is much tougher. Compare the two at your local store, you'll see the difference. The insulation on the wires in Romex are damaged much easier when you pull through conduit (been there, done that). You should either keep it in the Romex and use bigger conduit or use THHN. The inspector WILL care if he sees it. If I'm not mistaken, you must also use crimp connectors on the ends of the THHN if it will be attached to a screw terminal, such as that on an outlet.
  14. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    The insulation on the conductors of type NM-B cable is NOT THHN although it IS rated for 90 degree C. operation.

    THHN insulation may be applied to either solid or stranded conductors.

    The N signifies a nylon (or equivalent) outer covering over the 90 degree Centigrade thermoplastic insulation.

    T=thermoplastic insulation.
    H=high temperature (75 degree C.) and the second H=extra high temperature (90 degree C.) rating.
    N=nylon (or equivalent) outer covering.
  15. dabiz7

    dabiz7 New Member

    Messages:
    42
    When I was stripping the insulation off the Romex wires to connect to the oven, I noticed that the each wire (red, black, white) was stranded wire, not solid.
    Also, the insulation had a clear layer over top of the color layer.
    This looks exactly like THHN to me.

    Just to confirm, its ok to run the bare copper wire in the PVC conduit with the other wires (if I strip off the Romex jacket)?
  16. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    Nope.



    You can fit the cable into the 3/4 conduit. You just have to do it a piece at a time. Plan ahead and use no more 90's than necessary.
  17. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,726
    Location:
    Central Florida
    I seem to remember someone commenting once that it is explicitly illegal to do that -- the cable has to be pulled through the entire conduit run in a single pull.
  18. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    True....if you are pulling wire thru conduit.

    Here we are sleeving cable with conduit for protection.

    There is a technical difference.
  19. bartman

    bartman Telecomm Engineer

    Messages:
    2
    Location:
    new jersey
    I just found this site. I love it. This particular thread is exactly what I was looking for! I will post my question here rather than starting a new thread. But if I should post a new thread please let me know..

    I am running 6 AWG to a outdoor Hot Tub (50Amp). I need 75' of wire (indoor) from breaker box to the disconnect GFCI panel, located on the outside wall of my house. From the GFCI panel to the Hot Tub (outdoor)requires an additional 25' of wire.

    Do I run #6 awg NM romex for the 75' indoor section and pull THHN through pvc conduit for the outdoor 25' section? Or should I run the THHN all the way?

    The cheapest would be NM all the way and thread the sections of 1" conduit over it. Difficult but acheivable. But would this pass inspection?

    (fyi Many years ago I ran UF cable outdoors to a pool via conduit. The inspector made me rip it out a pull the THHN. I still dont understand that. The conduit was there to protect the wires should anyone dig.)
  20. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Either way is acceptable. If you run the individual wires inside they must be enclosed in conduit.


    No. The wiring between the disconnect and the hot tub MUST have an insulated equipment grounding conductor. The equipment grounding conductor must have green insulation and the entire run from the disconnect to the hot tub must be in conduit.


    It was the bare ground wire in the type UF cable that made the installation non-compliant.
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