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I am installing a new built-in oven, and while it has both neutral and ground pigtails, the manual states that they are "twisted together." I am interpreting this as "electrically connected."

Given the myriad of excellent explanations here on why the ground and neutral should only ever be bonded at the main panel, how does this not circumvent the protections offered by the single bonding location?

I understand that this isn't really my problem since the oven is UL listed and not really subject to NEC wiring practices, but I am curious because I have a subpanel, and if the ground between the main and the subpanel failed, it would seem all my grounds can now run through the neutral back to the main panel and I'd never know the ground wire was broken.

  • Does your built-in have a plug attached or is it meant to be hard-wired? The internal wiring is not subject to the NEC but the connection to your premises is absolutely subject to the NEC if your jurisdiction uses it. – ArchonOSX Nov 21 '17 at 11:00
  • It's hard-wired, and (while I know how to wire it properly), it also comes with instructions on connecting to either 3- or 4-wire supplies. Since I ran a new supply myself, I used a 4-wire supply (12/3 in this case). – Hari Ganti Nov 23 '17 at 1:19
  • Some appliances may come with a neutral / ground bond jumper in place internally but they usually have instructions on how to remove the bond jumper if you have a 4 wire supply. Since you already ran your own 12/3 supply then you should try to remove the bond jumper on the oven. – ArchonOSX Nov 24 '17 at 1:37
  • @ArchonOSX The manual doesn't contain any information about doing that – Hari Ganti Nov 25 '17 at 4:20
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That is absolutely correct. It is not OK to tie neutral and ground of an appliance. This is literally bootlegging ground.

"Ok" is not the same thing as "legal". It is legal to do this, only on dryers and oven/range, when installing on old wiring with no ground. This was a compromise worked out with the appliance industry, who feared losing sales. The rationalization is that dryers and ranges are rarely unplugged and moved, so a neutral wire failure is unlikely.

Unrelated, since then, Code now broadly allows retrofitting grounds.

Hooking up an appliance in this regime

There are only two legal ways to connect a range or dryer.

  • using a 3-wire connection (hot-hot-neutral no ground), you are to bond neutral to ground in the range or dryer.

  • using a 4- wire connection (hot-hot-neutral-ground), DO NOT bond neutral to ground in the range or dryer. This bond should be removed.

Using a 4-wire connection and still bonding neutral and ground would be a disaster for the reasons you cite.

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    I think you misunderstood me a little. It does have instructions for bootlegging the ground (stated as "where permissible"), but provides a 4-wire pigtail set. However, the instructions mention that, internally, the ground and neutral are twisted. I ran 12/3 to the appliance, so I am connecting 4-wire to 4-wire, but I can't do anything about how it's connected internally. – Hari Ganti Nov 23 '17 at 1:22
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    @HariGanti Weird. If you unhook power and neutral and ground, neutral to ground should be infinity ohms. Is that not so? It's always possible that a manufacturer is doing something they should not. – Harper - Reinstate Monica Nov 23 '17 at 5:00
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    I'll check when I get a chance. Currently, the oven (it's an oven) is in place, but I'll have to move it a little in the future for some remodeling work. Before I rewire it, I'll check the neutral to ground resistance. – Hari Ganti Nov 25 '17 at 4:21

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