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Condition: My house is 37 years old and our kitchen remodeler (not an electrician) did the following. He tapped into one of the oven’s 120 volt legs to power a 120 volt duplex receptacle. There is no neutral wire back to the panel for this duplex receptacle’s circuit, instead the remodeler used the ground wire connected to the oven’s 3-prong receptacle. The duplex receptacle is used to power the microwave and the warming drawer. All appliances are independent of each other. At times about 20 amps flowed to the microwave and the warming drawer. When using both of these appliances, touching their metal surfaces was required.

Remedy: We used the oven and warming drawer for some time before identifying the problems and having them rectified by licensed electricians and inspected by our city.

Question: While we never felt a shock, my conclusion is that because the oven’s ground wire was used as a neutral wire, the ground wire energized the metal on the oven and the microwave when the duplex receptacle returned current to the panel. We did not feel a shock because in our instance, the voltage was very low on the duplex receptacle’s neutral wire. Are these conclusions correct?

RelaxTax
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    The live/hot section of a device is supposed to be isolated from the housing/case, so you should not get a shock when everything is normal. The ground is suppose to be attached to the housing, in case hot does come in contact with it. With using the ground as neutral, there was no safety if something did happen. – crip659 Jun 22 '23 at 17:30
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    I'd send the licensed electrician's bill to the "kitchen remodeler". – FreeMan Jun 22 '23 at 18:00
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    Was the same wire connected to both the neutral and the ground on the receptacle? Or is the receptable ungrounded? – David Schwartz Jun 23 '23 at 10:34

2 Answers2

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used the ground wire connected to the oven’s 3-prong receptacle

An oven's 3-prong receptacle has neutral. It does not have ground. Ovens need neutral so the oven light can be 120V and use a standard incandescent bulb. (Yes, that is the reason these dangerous, ungrounded oven circuits still exist, heaven forbid you have to go to a hardware store and get a special 240V bulb for an oven!)

my conclusion is that because the oven’s ground wire was used as a neutral wire, the ground wire energized the metal on the oven

That's by design. In 1966 when they required grounding for everything else, oven and dryer makers howled and said this would ruin their business, and that it ought to be OK to attach dryer/oven chassis to the neutral. Yes, if the neutral wire broke, this would energize the chassis of the oven - however what are the chances of that? These connections are rarely disturbed. So it's a legally sanctioned bootleg ground off the neutral.

It sounds like your remodeler took that as inspiration to also bootleg the grounds of those 120V sockets, to fool the inspector's 3-light tester. Criminal fraud IMO. The remodeler should have installed GFCI outlets and labeled them "No Equipment Ground" and connected ground to nothing. It's still illegal to wire an ungrounded 120V new outlet post 1966, but that at least removes most of the danger.

So this clown put your family in danger for a quick paycheck. I'd send my lawyer in for a class action and subpoena their records of every customer to see who else they're trying to murder.

Guy probably does it on every remodel and thinks there's nothing wrong with that. I would raise holy hell just to educate the guy. Go after their insurance for the cost of repair.

We did not feel a shock because in our instance, the voltage was very low on the duplex receptacle’s neutral wire.

Yes. What they did works, as long as nothing goes wrong. Nothing went wrong for you, apparently. I'm surprised you found it other than by something going wrong - this is a sleeping danger.

Harper - Reinstate Monica
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  • You are right, I did notice something askew. When creating a circuit breaker map for my panel, I did not find breakers for the microwave or warming drawer. After noting that, things got expensive . . .. removal of appliances, two dedicated 120 volt receptacles, city inspection and reinstall of appliances. – RelaxTax Jun 23 '23 at 14:23
  • I thought the "No Equipment Ground" GFCI was allowed by code in a wide range of situations where existing wiring doesn't provide a ground, because doing so would be so much safer than any practical alternative. – supercat Jun 23 '23 at 21:54
  • @supercat yeah, it would be illegal for the contractor to have use N-E-G labeled GFCIs there, but it would have eliminated the vast majority of the danger. The guy's insurer (if any) would appreciate it! – Harper - Reinstate Monica Jun 23 '23 at 22:20
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Under normal conditions, the ground is still held at (or near) zero volts, even when being used as a bootleg neutral. However, if the ground wire were to fail or get disconnected, then the neutral connection to the ground could allow the metal chassis to be energized to 120 volts which could be deadly.

Also, the ground wire is often undersized, on the theory that it doesn’t normally carry current. This means that using it as a neutral could overload it and cause a fire. However, using the ground on a 40+ amp circuit as a 20 amp neutral is unlikely to overload it.

Finally, I should note that tapping a 20 amp receptacle off of a 40+ amp circuit is bad by itself as it is not properly protected against overloads.

DoxyLover
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