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I have to add a 50 amp circuit to the sub panel in my garage. I found one of the open knockouts in the top of the panel to have a blue flexible conduit looking stuff in it which runs up into the ceiling. I thought, "cool, this guy planned ahead". So my plan was to just this to run the cable up into the ceiling then down a wall where I need the receptacle.

Question is, IS this conduit, and can I use it for this purpose? I'll be running 6-3 cable (romex, I suppose).

  • What size is the conduit, and where does it go to? Also, is the conduit properly fitted to the KO in the subpanel box (cabinet), or is it flapping in the breeze in there? – ThreePhaseEel Dec 4 '18 at 0:03
  • The conduit is at least 1" ID, possibly 1.25". – slambeth Dec 5 '18 at 15:44
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Smurf tube. The name its mom uses to yell at it is "Electric Non-metallic Tubing" or ENT.

You will need to run a separate ground wire since it is not metallic.

You have to watch out for conduit fill, there are fill calculators on the web.

If you plan 4 or more circuits in that conduit, come back and ask us about derating, but you probably won't have space for that.


DIYers must be careful when designing conduit pulls. Too difficult a pull requires an electrician's truck full of pulling tools, and the owner of that truck typically will only agree to do the whole job.

Most people go straight for multiconductor cable because that's what they know. Meet THWN-2: it is an individual wire with a special jacket made for pulling. It is typically stranded and much more flexible than cable. Conduit pulling is much easier. But it lacks the armor of cable so it cannot be used outside conduit.

So you have 3 choices: a) cable all the way including through the conduit, b) extend the conduit (using any conduit type) to your destination and use THWN-2 wires, or c) THWN-2 through conduit to a junction box, there splice to a cable. Any of these are a compromise on difficulty.

I would extend the conduit just because that's my better skill.

  • Derates are independent of conduit type. – ThreePhaseEel Dec 4 '18 at 2:43
  • @ThreePhaseEel I thought maybe the 60C rating of this conduit would reduce the figure from which you derate, e.g. When we derate from 90C we are usually dealing with both wire and conduit good for 90C. – Harper Dec 4 '18 at 2:50
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    I don't see this (wire rated to 90C, conduit rated to 60C) as any different as derating a NM cable -- the conduit temperature limit applies independently of the derate limit. – ThreePhaseEel Dec 4 '18 at 3:45
  • @ThreePhaseEel okay, works for me. – Harper Dec 4 '18 at 3:46
  • If I just run this stuff through it, does i matter? amazon.com/Cerrowire-147-4203A-25-Feet-Stranded-Ground/dp/… can't that wire be run right in the wall with no conduit? – slambeth Dec 4 '18 at 16:12

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