Mike Dolt Enterprises
Mike Dolt Enterprises
User: yrenner, Location: Oregon
Asked on: Monday, March 24, 2025 at 4:29 pm EDT
Answered on: Monday, March 24, 2025 at 4:50 pm EDT
Question: Hello,First time poster here. This is a common question but answers differ. I am not looking for the "right" answer, but any and all acceptable answers. I have a decent understanding of terms (as might be found in the NEC) and DIY experience. I am in the middle of a kitchen remodel and need to make a decision. The new double oven, of course, will come standard with 4 wires. The wire coming into our 1966 house is, of course, a 3 wire SEC cable (two hots and one bare stranded aluminum, pictured below). I understand this wiring configuration utilizes a "bootleg" ground that is no longer code compliant and potentially risky (one might say potentially lethal), but still allowed under an exception. As a matter of fact, the new oven we are purchasing includes wiring instructions for a 3-wire system like mine.In principle, I would prefer to replace the existing SEC cable for an appropriate 4-wire conductor, but DIY remodeling has its limitations. Here's what I know:The sheathing of the existing SEC cable is in very good condition under the crawl space.The run itself is no more than 25 feet and terminates at the main electrical panel and a 40 amp breaker. I opened the panel this morning and verified that the wiring appears to come in from the attic, which I don't quite understand because it first enters from the crawl space, but there you have it.I'm unsure if I have an actual grounding rod, but I do have bare copper bonded to the galvanized pipes in the crawler. (NOTE: I have already replaced 75% of the galvanized pipe with PEX).Now for my questions.If I am not able to replace the existing SEC cable, could I simply run a bare copper EGC from the junction box to the electrical panel and call it good?If solution #1 is not advisable, could I run the bare copper EGC to the same location where the galvanized pipes are grounded (as previously suggested in this thread), since presumably the existing copper EGC travels back to the electrical panel?If neither solution will work, what do you all suggest?
Okay, let's break down your situation and explore the options, keeping in mind safety and code compliance (even if you're leaning on an exception).
Understanding the Situation 3-Wire vs. 4-Wire
The fundamental issue is separating the neutral current path from the grounding (equipment grounding) path. In a 3-wire system, the neutral conductor is also used as the equipment ground. In a 4-wire system, the neutral and ground are separate back to the main panel.
"Bootleg Ground"
Connecting the appliance chassis to the neutral in a 3-wire system creates the "bootleg ground" situation. This can be dangerous because if the neutral connection becomes loose or breaks, the appliance chassis could become energized at a dangerous voltage.
NEC Exception
The National Electrical Code does allow the use of a 3-wire connection to an existing range/oven only in specific circumstances: It must be an existing branch circuit. The receptacle must be replaced with one marked "Suitable for Use Without Equipment Ground". A grounding-type receptacle is permitted if GFCI protection is provided.
Addressing Your Questions1. Running a Bare Copper EGC from the Junction Box to the Electrical Panel
Code Perspective
The NEC generally requires that any new branch circuit wiring conform to current code requirements. Since you are putting in a new oven and therefore messing with the wiring, running an additional EGC back to the electrical panel would technically be the "right" thing to do.
Practicality
If you can find a viable route from the oven junction box back to the electrical panel, this is the best option for safety.
This means a continuous, unbroken run of appropriate-sized bare or green insulated copper wire. Important Considerations
Wire Size
The EGC must be sized according to the overcurrent protection (your 40A breaker). Refer to NEC Table 250.122. For a 40A breaker, the EGC must be at least #10 AWG copper.
Termination
Ensure the EGC is properly terminated at both ends:
Oven Junction Box
Connect to the oven's grounding screw or lug.
Electrical Panel
Connect to the grounding busbar in the main panel. The grounding busbar must be bonded to the panel enclosure, and the panel enclosure must be grounded to the grounding electrode system (ground rods, water pipe, etc.).
Physical Protection
Protect the EGC from physical damage where necessary. Consider using conduit or running it alongside the existing SEC cable.2.
Running the Bare Copper EGC to the Grounded Galvanized Pipes
Absolutely NOT Recommended and likely a Code Violation! The NEC (National Electrical Code) specifically prohibits using metallic water pipes as the sole grounding electrode. There must be a supplemental grounding electrode, such as a ground rod or ground ring. You can not just tap into the piping. Why? Piping Changes
You've already replaced sections of galvanized pipe with PEX, which is non-conductive. Any future replacements could interrupt the grounding path.
Corrosion/Bad Connections
Galvanized pipe is prone to corrosion, which can create high-resistance connections, rendering the grounding ineffective.
Reliance on the Water Company
Your grounding system would depend on the water company maintaining their metallic piping. If they switch to PVC, your grounding is gone.3.
What to Do If Neither Option is Ideal Consider Profession Installation
Honestly, if you are uncomfortable, call in a qualified electrician to asses the situation. This is not the place to save a few bucks and have safety concerns later.
Really Explore Cable Replacement
The best, code compliant solution would be to just replace the 3-wire cable with a new 4-wire cable.
Additional Points to Consider Verify Grounding Electrode System
Confirm that your house has a proper grounding electrode system (ground rods, ground ring, or connection to a metal water pipe supplemented by another electrode). This is CRITICAL for safety.
GFCI Protection
If you absolutely cannot run a separate EGC, consider using a GFCI-protected receptacle for the oven. While this doesn't replace a proper ground, it provides a degree of shock protection.
Local Codes
Check with your local building department or a qualified electrician to ensure compliance with local codes, as they may have stricter requirements than the NEC.
In Summary: Your best option is to run a separate, properly sized EGC back to the main panel's grounding bus. This provides the safest and most code-compliant solution. Connecting to the galvanized pipes is NOT recommended.* If you're unsure about any of this, consult with a licensed electrician. Your safety is paramount! Flag for review