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USA Home, built in early 80s.

I was looking at my homes oven wiring and noticed the 40 Amp circuit has a special ground wire. It appears to be twisted/stranded silver wires.

I could not see if a neutral was also included in the same cable.

Is this a common type of cable and what would it be called?

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  • That's just an aluminum grounding wire. Are you sure this goes to your oven and is not part of the supply? It looks too small to be on the supply, but looks too big for a 40A circuit (even for aluminum).
    – tnknepp
    Mar 29, 2021 at 16:52
  • Yeah for sure going into the same jacket as the oven breaker wires.
    – justing
    Mar 29, 2021 at 16:55
  • Are the rest of your oven wires aluminum? Guessing they are. By the way, when I said the wire looks too big I was thinking of copper. Aluminum will be a larger gauge, so ya, this is just a stranded aluminum cable. If you can count the number of wires in the cable then you can determine if you have a neutral (if 4 then you have a neutral, if 3 then no neutral)...or you could open the outlet on the oven end (with power off of course).
    – tnknepp
    Mar 29, 2021 at 17:03

2 Answers 2

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Noting the irregularities in the way the strands are spiraled, that is certainly SE type cable, or "Service Entrance" cable. Service entrances (weatherhead to main panel) are run hot-hot-neutral with no ground, so naturally, SE cable provides exactly that. The bare wire is neutral, not ground.

Use of SE cable for ranges was legal in the 1970s, and as such, it is "grandfathered" today. It is neutral, not ground, which means your range has a 3-wire ungrounded connection, also legal in the 1970s.

While it's grandfathered to the inspector, it is not grandfathered to the reaper. 3-wire connections have a fatal flaw: in this setup, the chassis of the range is bonded to the neutral wire. If it has a simple and common contact problem, it energizes the chassis of the range with lethal voltage when the oven light is on (i.e. door is opened).

When fatalities happen this way, it is reported by the press as miswiring which is untrue: it was wired correctly but neutral had poor contact. Which happens.

The new doctrine is to provide a separate ground wire; or; fit GFCI protection at the breaker. Both of these solutions require removing the bad-news bonding strap inside the range that ties the chassis to neutral.

Merely removing the bad-news bonding strap is not enough; now the chassis will be energized by any ground fault (which grounding or GFCI would have detected).

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  • Thanks Harper, great info. Why would the oven light circuitry energize the chassis then? Is it using the chassis as a 120V return normally?
    – justing
    Mar 29, 2021 at 21:59
  • I guess the bonding strap would ensure that actually. Thanks again.
    – justing
    Mar 29, 2021 at 22:07
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    @justing exactly. It's using the neutral in the normal fashion as one would expect, the oddity is the chassis being bonded to neutral. Mar 29, 2021 at 22:12
  • Thinking on this more, wouldn't the 120V loads on the range trip a gfci breaker at the panel due to mismatched currents on the hots? Or does it not trip on that mechanism like outlet GFCIs?
    – justing
    May 11, 2021 at 23:25
  • @justing a 2-pole GFCI actually has 3 wires going though the comparator. 2 wires have current flowing one direction, another has current flowing the other direction. (and this changes dynamically). As long as the currents "add up" (cancel each other out considering direction), the GFCI will not trip. However, a GFCI on a 3-wire range requires ground not connected to neutral. May 12, 2021 at 2:26
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To me that looks like it would be for the Stove and that is the neutral/ground. Based on the information you supplied I would assume you have a stove that needs 220 and based on when the house was built, it did not need a ground and a neutral in the same wire. Today, you would have a ground, neutral and 2 hot wires but back then 3 wire was common in this type of situation and the ground and neutral was basically shared in that wire.

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  • I guess I should also add they did this as aluminum wire is a lot cheaper and by code you can use it on anything greater then 8 gauge wire. It is not a safety hazard by its self, but it is no longer to code and you must now run 4 wire to such appliances that need a neutral. Some appliances don't need a neutral and can still have 2 hots and a ground but that's another story... lol Mar 29, 2021 at 17:46
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    Actually aluminum is legal for any size wire. However it has to be the new AA-8000 alloy, and terminations must be rated for aluminum. You could wire your whole house in it if you really wanted to, and you'd pass inspection fine. But you'd have trouble selling it because of home-buyer prejudices. Mar 29, 2021 at 20:22
  • Thanks Keith, I will have to see what I can find once I pull the old oven out. The other answer makes it sound like it is probably the neutral and has no dedicated ground run. I assumed the red and black covered conductors were copper, but they probably are aluminum as well then. I will have to check that out closer next time.
    – justing
    Mar 29, 2021 at 22:03

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