# Wires. Same Circuit. Different Conduits



## cabletie (Feb 12, 2011)

You found the right article. 300.3(b). B1-B4 more than likely don't apply. 

Easiest would be use conduit as ground and tape your existing ground white. I know taping a #6 grounded conductor white is not allowed, but what are you going to do. Looks like you couldn't even fit it if you pulled it out and pulled in two #8s for a ground and neutral.


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## cabletie (Feb 12, 2011)

McGraw Hill 2008 Handbook

300.3. Conductors. Part (A) requires that single conductors described in Table 310.13(A) must be used only as part of one of the wiring methods covered in Chap. 3. This basically means that the various insulated conductors recognized in Table 310.13(A) may not simply be strung overhead, without benefit of being incorporated into a cable assembly or otherwise protected and supported by con- duit or tubing. The Exception to part (A) recognizes the permission given in 225.6, where individual conductors are permitted to be run as “open conductors” in overhead feeders and branch circuits installed outdoors, as well as in festoon lighting.
Part (B) requires that all conductors of the same circuit—including the neutral and all equipment grounding conductors—must be run in the same raceway, cable tray, trench, cable, or cord. Part (B)(1) recognizes the use of separate race- ways and cables, where circuits are made up of multiple (two or more) sets of conductors or cables in parallel. The exception that follows correlates with 300.5(I) Exception No. 2 for isolated phase installations. Part (B)(2) in that rule notes those very specific and unusual sections of the NEC, where an equipment grounding conductor may be run separately from the other conductors of the cir- cuit such as for DC circuits and for retrofits under the provisions of 250.130(C).
Part (B)(3) requires taking steps to prevent induced currents where nonmetal- lic or nonmagnetic sheathed conductors are run through metallic enclosure walls with magnetic properties as covered in 300.20(B). The second sentence gives a similar warning for Type MI cables and references 332.31, which addresses the concern for induced currents. Both of those other rules discuss methods for pre- venting induced currents.
Part (4) of 300.3(B) permits limited use of a pull box equipped with a terminal block for the connection of the system neutral, as the point of origin for branch circuit neutral conductors. That is, a properly sized neutral is run to the pull box—which is connected by an auxiliary gutter to a column-width panelboard— from the panelboard, and the individual branch-circuit neutrals may be run from the pull box and need not go back to the panelboard where the hot conductors originate. This saves space within the panelboard, but is only permitted for column-width panelboards connected by an auxiliary gutter to a pull box that is manufacturer-equipped with a neutral terminal block. Note that there is no inductive heating in this arrangement and it is arguably permitted even without this permission. Every ampere that comes up the auxiliary gutter from the panel on a branch-circuit conductor is equaled by an ampere of current moving down the same gutter space to the panel over one of the feeder conductors.


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