Do I need the ROMEX insulation on 10-2 wiring?

[kooshball]

I am going to add an outlet very close (16") to an existing one and I will reconfigure the existing outlet box as a junction box, with the infeed and have two outfeeds going to each outlet. Things are getting tight and I was wondering if I could remove the outermost ROMEX stamped insulation and just run the individual wires to where they need to go (they are also insulated) or if this is a no-no? The run is short, the boxes and conduit are PVC so there is little to no chance that I snag and cut into the insulation as you might in a long run in metal conduit / fixtures.

Let me know; thanks.

 

[bobby g]

If the wires are going to be in conduit, individual wires is the correct way to do it.

bobby g

 

[kooshball]

That is what I figured; I was just waiting for this response; wire in hand....

And now to tie it all in.

 

[scsmith42]

If the wires are going to be in conduit, individual wires is the correct way to do it.

bobby g

+1. Matter of fact, it's preferred not to run romex inside of conduit because you will have more heat build-up.

 

[Bryan S]

I am judging from your post that the wires you are pulling will not be in conduit. If I am judging correct, the answer is no, do not remove the outer covering from the cable.

 

[Charles Lent]

If you are using conduit, the wires inside should be single conductors and not Romex. If you are running Romex all of your Romex should be inside the walls or protected in some way. If it will be mostly on the surface you should be using single conductors in conduit and not Romex in any garage, workshop, or basement area where it may be easily damaged, in other words, from the floor up to 8' above the floor.

Charley

 

[Bas]

Let me add yet another answer to the mix. From what I read, you're allowed to sleeve NM (non-metallic) cable (aka "Romex") for protection purposes in conduit. But, you shouldn't strip the outer jacket. The insulation on the individual wires inside NM cable is not equivalent to the insulation used for individual conductors. Will it matter? From a safety point of view, probably not if it's a short run. Will it pass inspection? Who knows. I'm not an electrician.

 

[ehpoole]

Bas is correct. If you are going to abide by code, Romex wiring is only rated for use with its outer jacket, save for the 6-8" stripped off each end for termination. The insulation of the individual Romex conductors is not nearly as tuff as it needs to be if used as individual conductors, the outer jacket is responsible for providing that extra 'tuffness' and protects the individual wires while also functioning as a sort of self-contained non-metalic conduit for the enclosed bundle of wires. If you are going to run Romex within conduit, it must be run with its outer jacket intact. The excess volume created by the Romex outer jacket is the reason why you do not normally see Romex run in smaller conduit sizes.

To properly wire your new outlets, you will have to go to your nearest hardware store or electrical supplier and obtain some #12 copper THHN or THWN wire which IS rated for use as individual runs (you will want atleast the necessary length in white, black, green and possibly red if you need 240 or if you will be running a 120-120 split with shared neutral).

Now for your second potential issue. You state that your box -- and/or conduit -- is getting tight for space. There are maximum fill limitations for both the receptacle box AND your conduit and you should avoid exceeding those maximum fill requirement.

With respect to the conduit, you are permitted a maximum of 40% fill where fill is calculated as the total cross sectional area of the wires divided by the cross sectional area of the conduit (actual inside diameter, not nominal diameter). To do the raw calculations one needs a dial caliper (1/1000") from which you can then perform the calculations. One can also reference the NEC tables for common individual conductors (though there are no table entries in my books for Romex, so you would have to make that calculation yourself [width multiplied by height = sq. inches).

Cross Sectional Area & ID for Common Conduit:
===================================
1/2" EMT = 0.622" ID = 0.304 sq. in. (40% yields 0.1216 sq. in. usable)
3/4" EMT = 0.824" ID = 0.533 sq. in. (40% yields 0.2132 sq. in. usable)
1/2" Sch40 PVC = 0.602" ID = 0.285 sq. in. (40% yields 0.114 sq. in. usable)
3/4" Sch40 PVC = 0.804" ID = 0.508 sq. in. (40% yields 0.2032 sq. in. usable)
1/2" Sch80 PVC = 0.526" ID = 0.217 sq. in. (40% yields 0.0868 sq. in. usable)
3/4" Sch80 PVC = 0.722" ID = 0.409 sq. in. (40% yields 0.1636 sq. in. usable)


Maximum # Conductors Allowable for Select Conduit (if all identical)
================================================
EMT Sch. 40 PVC Sch 80 PVC
------------- | ------------- | ------------- | Cross Section
Gauge | 1/2" 3/4" 1" | 1/2" 3/4" 1" | 1/2" 3/4" 1" | Per Wire
--------- | ---- ---- ---- | ---- ---- --- | ---- ---- --- | -------------
14 TH*N | 12 22 35 | 11 21 34 | 9 17 28 | 0.0097 sq. in.
12 TH*N | 9 16 26 | 8 15 25 | 6 12 20 | 0.0133 sq. in.
10 TH*N | 5 10 16 | 5 9 15 | 4 7 13 | 0.0211 sq. in.
* You will need to calculate the sq. in. equivalent of your Romex cable
** I fear vBulletin is going to foulup the table spacing, so copy to your clipboard and add appropriate spacing to read more clearly.

With respect to the receptacle box you must allow for a minimum volume per wire that terminates in the box (any wire end that does not pass straight through the box with an unbroken connection). This is a more complex calculation for an amateur so I'm going to suggest going with a simple layman's gauge of box fill: If you have to stuff your wires, wirenuts, or receptacles into the box then it is very much overfilled. To solve the overfill problem you can simply add extension rings to the box to increase the available volume, thus avoiding the risks associated with overfilling the box. This may seem unnecessary to the amateur, but when a box is intentionally overstuffed it greatly increases the risk of damaging wire insulation and seperating tied wires (wirenuts) which can result in loose, intermittent, connections which can result in arcing and eventually lead to fire. Overfilling also increases the risk of heat buildup (such as from loose arcing connections) causing damage to the insulation of nearby wires resulting in undesirable conductive bridges and shorts.

HTH

 

[kooshball]

Wow; that is excellent info...thank you!

Looks like I need to tweak some things a bit, and I am glad to have this as a guide.

 

[kooshball]

For a 20A, 240V circuit I really only need 12ga wiring right? If so, this will allow for all the clearances mentioned above if I just go down to THNN 12ga in the existing 1/2 grey conduit and boxes and since these runs are a total a 3' this should be a quick fix.

 

[Bas]

For a 20A, 240V circuit I really only need 12ga wiring right? If so, this will allow for all the clearances mentioned above if I just go down to THNN 12ga in the existing 1/2 grey conduit and boxes and since these runs are a total a 3' this should be a quick fix.

Correct, for a 20A circuit you need 12 gauge. Since you only need 3' (well, 6' since you need to conductors, plus extra to make the connections, plus ground), you can pretty easily buy this by the foot at Lowe's or Home Depot. If you're coming to the picnic...I have a quite a bit of 12 gauge THNN wire (red color) left over. I'd be happy to snip off 10ft or so for you to use for free.

 

[ehpoole]

Correct, for a 20A circuit you need 12 gauge. Since you only need 3' (well, 6' since you need to conductors, plus extra to make the connections, plus ground), you can pretty easily buy this by the foot at Lowe's or Home Depot. If you're coming to the picnic...I have a quite a bit of 12 gauge THNN wire (red color) left over. I'd be happy to snip off 10ft or so for you to use for free.

#12 copper will be a fine substitute for a 20A 120V circuit (the #10 is a step above code and further reduces voltage drop, but voltage drop over a few feet is negligible). However, while he may use red wire as a substitute for the black (hot) conductor, it may not be used as a substitute for the white (neutral) or ground (either green or bare, but I prefer insulated green ground wires -- esp. in a tight box.

 

[Bas]

..it may not be used as a substitute for the white (neutral) or ground (either green or bare, but I prefer insulated green ground wires -- esp. in a tight box.

+1. (I was going to bring the roll of green wire too...funny how you always have 2/3 of a full roll over at the end of a project ) I like to keep my wiring ultra simple: Red for 240, black for 120, white for neutral, and if at all possible, not use a neutral as hot. Yes, you can mark it, most of the time the cost to run a new wire is negligible.

 

[kooshball]

+1. (I was going to bring the roll of green wire too...funny how you always have 2/3 of a full roll over at the end of a project ) I like to keep my wiring ultra simple: Red for 240, black for 120, white for neutral, and if at all possible, not use a neutral as hot. Yes, you can mark it, most of the time the cost to run a new wire is negligible.

Bas, thanks for the offer but I wont be able to make the picnic. I picked up the required wire today and have everything installed. I really appreciate the offer and all the great advice.