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I mistakenly ran 18ga twin lead through plastic conduit out to power 12 volt lights. Never hooked up. Now I want to power a .68 amp 120V pump on a water feature. Too many 90 degree elbows to be able to pull and replace the wire, I believe.

I read in my 1999 electical manual that I can safely use a GFCI on this ungrounded circuit at the terminus.

  1. I want to make sure this is OK.

  2. What about making a separate ground via a earth rod at the terminus?

Don't want to create a hazard for anyone of course, but I am trying to avoid having to but a new 12V pump and transformer or running all new service to the location.


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2 Answers 2

You're sadly screwed here on multiple fronts. First off, although 240.4(D)(1) provides provisions for protecting 18AWG conductors, they can't be applied to a branch circuit due to 210.20(A)(4):

(4) Other Loads. Branch-circuit conductors that supply loads other than those specified in 210.2 and other than cooking appliances as covered in 210.19(A)(3) shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG.

Furthermore, the "twin lead" 18AWG you refer to in your OP is either speaker wire, which isn't listed for 120VAC use to begin with, or a type SPT-2 flexible cord (lamp cord), which can't be used for permanent wiring due to 400.8:

400.8 Uses Not Permitted. Unless specifically permitted in 400.7, flexible > cords and cables shall not be used for the following:

(1) As a substitute for the fixed wiring of a structure

(2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors

(3) Where run through doorways, windows, or similar openings

(4) Where attached to building surfaces

Exception to (4): Flexible cord and cable shall be permitted to be attached to building surfaces in accordance with the provisions of 368.56(8)

(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

(6) Where installed in raceways, except as otherwise permitted in this Code

(7) Where subject to physical damage

Finally, the excess elbowing in your (PVC) conduit run violates 352.26:

352.26 Bends - Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes.

In other words, this is what those funky "conduit body" things are for...

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The wire needs to be designed to handle the capacity of the circuit it's attached to, not the device that is plugged in. Otherwise, if anything is plugged into the end, or if there is a short, that draws more power, but not in excess of the circuit breaker, you would have a fire risk. I don't have a copy of the NEC, but to the best of my knowledge, in the US, a 15 amp circuit needs a 14 gauge wire, a 20 amp circuit requires a 12 gauge, and a 30 amp circuit requires a 10 gauge. Therefore, your 18 gauge wire is insufficient to attach to any standard circuit breakers that I've seen.

To answer your second question, you could install a separate ground for the other end of the connection and wire a gfci to that, assuming that the existing wiring were adequate for the circuit.

To fix the conduit, I would eliminate any sharp 90 degree turns and if it runs over a long enough distance, break the run by going up to an access panel.

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