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Old 12-16-2008, 08:34 AM   #16
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Shocking kitchen appliance


Ok, if no ground wire connected to mixer outlet nor to mixer outlet electrical box, then it is looking almost sure the problem is with the mixer. (And there are no stray wires touching the metal electrical box which the mixer is plugged into. A hot wire touching the metal electrical box could cause the hot to contact the metal mounting brackets of the outlet and flow up the 3rd ground wire to the metal case of the mixer.)

Also if this is an *old* mixer, then more likely to have a problem with it. Old electric motors tend to leak to ground due to grease and crud building up inside the case.

I would still advise checking what is grounded or not grounded and of course put it on your "to do" list to rewire as necessary so you have properly grounded outlets.

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Old 12-16-2008, 05:39 PM   #17
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Originally Posted by cantre44 View Post
yes the gfci shood have tripped yet doesnt always. could be many things. bad gfi...wired wrong gfi..."" non grounded service "" make sure service panel is grounded properly, water meter is jumpped out properly, and hot water hank is jumpped out. call me if u have ? 978-747-7314 THE E MAN
If the current flow is below the threshold for the GFCI, it won;t trip.

and to the "non grounded service"; that makes no difference. A GFCI is a differential relay and all it concerns itself with is current flow on the hot compared to current flow on the neut. Ground, or lack of it, has nothing to do with the GFCI. As a matter of fact, a GFCI is the required work around for non-grounded receptacles.
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Old 12-17-2008, 03:44 AM   #18
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There is a good lesson here for those not familiar with how a GFCI works... Yes, we can be killed, even with a working GFCI.

To oversimplify it, if we are connected to the hot and neutral/fault, you become the load, and the GFCI will not notice the difference; a hairdryer does not trip the GFCI, and if you 'become' the hairdryer, you will not trip the GFCI... but your hair will be dry and you will be dead.

To the OP, do not assume you have a bad GFCI right off the bat, just because you got shocked; there might be a much more dangerous situation going on, that the other members are discussing.

I am posting this for general information; I know some of you guys can probably state it better, but I didn't find this in the posts in this thread.
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Old 12-17-2008, 07:36 AM   #19
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I sincerely doubt that your bran-new KitchenAid mixer is defective.
My first thought was that the ground conductor of your ungrounded 12/2 NM cable was picking up phantom voltage from the current carrying conductors, but when you said that the ground conductor never leaves the sheath, I took that to mean that the ground conductor of the 12/2 NM does not terminate inside the outlet box or to the receptacle itself, and therefore could not cause the appliance to become energized.

The appliance manual states that the appliance must be connected to a properly grounded receptacle. This is most likely due to a line filter that is connected at the input to the ground wire. These filters consist of capacitors and inductors. Capacitors will conduct a small amount of AC current from hot to ground under normal conditions.
If the receptacle into which this appliance is not grounded, then this "stray" current from the line filter will cause anything connected to the equipment ground to become "live" with this leakage voltage.
When you place yourself between this voltage and a good ground, you become the conductor of current. You will feel a slight shock if the voltage is not very high.

I suspect that the caps used in the line filter are fairly low value (0.01, or 0.1uf). At 60Hz, the reactance would be 26.5K ohms for a 0.1uf, and 265K ohms for a 0.01uF. AT 115VAC, you would get 4mA through the 0.1uF cap, and 0.4mA through the 0.01uF cap.
With your body acting as additional resistance, even the 0.1uF cap would not cause enough current to trip a GFCI.

So, my best educated "guess" is that there is absolutely nothing wrong with your appliance. What you need is to get an electrician to install a properly grounded receptacle (GFCI) in the kitchen.
Since you already have part of the circuit wired with 12/2 with ground, it might be fairly simple to find the point at which this cable runs into the ungrounded wiring, and rewire the circuit from the panel to that point.
If there isn't enough of the ground conductor protruding from the sheath of the 12/2 coming into the outlet box to attach a pigtail and ground it properly to the receptacle and the box, you will need to rewire that part of the circuit as well.

In the mean time, DO NOT USE THE APPLIANCE WITHOUT A PROPER GROUND!!!

BTW, my sister recently purchased a KitchenAid mixer, probably the same one you have. I haven't read the manual, but hers is plugged into a GFCI receptacle that has a proper ground, so there are no problems.
Perhaps I can use my capacitance meter to check the capacitance between the ground prong and the hot to confirm the capacitance I was talking about.

Edit: Since there will also be a capacitor from neutral to ground, the filter will form a voltage divider (with the open ground being the center point), so the voltage you get will be even lower than what it would be if the cap were only from hot to ground.
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Old 12-17-2008, 09:25 AM   #20
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I measured the capacitance at the plug of my sister's KitchenAid mixer (which may be the same one the OP has).

Hot to Ground: 0.316nF (0.000316uF)
Neutral to Ground: 1.255nF (0.00125uF)
Hot to Neutral: 0.318nF (0.000318uF).

With these values, there would not be anywhere near enough current through the caps at 60Hz to trip a GFCI, or to cause a serious shock.
However, with the warning as stated in the manual, as clear as it is, why would anyone knowingly disregard it?

The warning in my sister's KitecenAid manual:

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Old 12-17-2008, 09:41 AM   #21
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Quote:
Originally Posted by KE2KB View Post
I measured the capacitance at the plug of my sister's KitchenAid mixer (which may be the same one the OP has).

Hot to Ground: 0.316nF (0.000316uF)
Neutral to Ground: 1.255nF (0.00125uF)
Hot to Neutral: 0.318nF (0.000318uF).
More Homework: How much of that capacitance is due to the cord itself?
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Old 12-17-2008, 10:06 AM   #22
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More Homework: How much of that capacitance is due to the cord itself?
Interesting point. I had not considered the cord. I would think it very low, in the order of pf, not nf, but we're not talking about a lot of capacitance in any case.

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