Getting Shocked

[hannibalmdq]

So, long post incoming.

For a while now I've suspected I was getting a little buzz occasionally when using my electric kettle. It's a 1500w 120v 6.5 gallon kettle. The housing is a hot pod.

Every time it happens, I double check my wiring with my multi meter. It always checks out. The circuit is isolated from ground, and the kettle itself is well connected to the ground prong. I've also checked the gfci outlets with a gfci tester. All things being equal, there no way I should be getting shocked. I've written off as my imagination.

Tonight I realized my kettle is close enough to the hose spigot that I could verify the potential between the kettle(again, grounded) and another ground.

It came back 1v.

I cut a length of 12 gauge wire and touched the kettle to the spigot. Small sparks. No gfci trip.

I've been running through what conditions this could happen. The only thing I can figure is that the kettle (which I know had a good connection to the ground prong) has a different voltage potential than the grounded pipe.

This is bothersome for a number of reasons. I tested the other ground receptors on the gfci to the pipe both under load and not. No difference in potential.

But under the load of the kettle, the grounded kettle remains at a different potential than the grounded pipe.

Thoughts? It's an old house (135 years). I'm wondering if maybe there's an issue with the wiring somewhere else in the house that's causing the load of the kettle to change the potential the ground circuit.

 

[lschiavo]

How old is the service entrance? It's the bonding to the water system done properly? The water meter should be jumped. The hot and cold on the water heater should be jumped in case of dielectric unions. Sometimes repairs of metal water pipes are done with plastic creating an unbonded section of the system. Those should be jumped as well. Around here, we also bond the gas line. Just a few things to look into...

 

[hannibalmdq]

Panel is grounded via a really thick piece copper wire to the copper pipe right where it enters the house. I live in the city, so I don't have access to the meter itself.

 

[lschiavo]

If you read 1V, Ohm's law says should have 200-1000 ohms resistance between your kettle and spigot to have between 1 and 5 mA of current. 1mA is the threshold to feel the current and about 5 is where the gfci will trip.

Easiest fix is to bond your kettle or control panel to the closest water line like you did temporarily with the piece of #12.

 

[hannibalmdq]

If you read 1V, Ohm's law says should have 200-1000 ohms resistance between your kettle and spigot to have between 1 and 5 mA of current. 1mA is the threshold to feel the current and about 5 is where the gfci will trip.

Easiest fix is to bond your kettle or control panel to the closest water line like you did temporarily with the piece of #12.

Well that would certainly ground the kettle, but right now I'm trying to ascertain why the kettle, grounded via the grounding prong in the outlet, would be at a different potential than the copper pipe.

Is it the element wiring leaking to the kettle, which I've checked is isolated many times, or if the load of the element on my house wiring forcing some voltage to the ground circuit?

 

[passedpawn]

Well that would certainly ground the kettle, but right now I'm trying to ascertain why the kettle, grounded via the grounding prong in the outlet, would be at a different potential than the copper pipe.

Is it the element wiring leaking to the kettle, which I've checked is isolated many times, or if the load of the element on my house wiring forcing some voltage to the ground circuit?

I'd be doubting the ground on your outlet. Maybe neutral, which carries current and thus can have a positive voltage when current is flowing. A simple tester would let you know.

When you say it's isolated power, what do you mean by that? Is it really on 120V isolation transformer?

 

[hannibalmdq]

Sorry, by isolated I meant I've verified with an ohmmeter that the hot and nuertal prongs on the kettle plug are not connection with the kettle or the ground prong. I've also verified the kettle itself is in connection with the ground prong. This should mean that the circuit is isolated from the kettle, correct? There shouldn't be any leakage of current from the element circuit right? I'm trying to figure out where the source of the voltage on the kettle is coming from. Assuming the element circuit isolated, could it be coming from the ground itself?

Would something like a crossed ground/neutral elsewhere in the house cause a small voltage on the ground when the element is under load? This is all speculation.

 

[flars]

You may find some useful information to solve your problem if you search "stray voltage".

 

[passedpawn]

Sorry, by isolated I meant I've verified with an ohmmeter that the hot and nuertal prongs on the kettle plug are not connection with the kettle or the ground prong. I've also verified the kettle itself is in connection with the ground prong. This should mean that the circuit is isolated from the kettle, correct? There shouldn't be any leakage of current from the element circuit right? I'm trying to figure out where the source of the voltage on the kettle is coming from. Assuming the element circuit isolated, could it be coming from the ground itself?

Would something like a crossed ground/neutral elsewhere in the house cause a small voltage on the ground when the element is under load? This is all speculation.

Yea, it's possible that ground and neutral are reversed. That could result in a voltage if other devices on same ckt were on and conducting on that neutral. Since they both get tied together back at the breaker box, a circuit tester wouldn't indicate a problem. Best think is to turn pwr off at the breaker and pull the outlet and make sure neutral is white and gnd is green/bare.

Also, ohm neutral and ground and make sure there's continuity.

Maybe also check your GFCI. It should have a test button - use that and make sure it trips.

 

[lschiavo]

I tested the other ground receptors on the gfci to the pipe both under load and not. No difference in potential.

But under the load of the kettle, the grounded kettle remains at a different potential than the grounded pipe..

What does this mean? Are you saying you checked other Receptacles? Are they on the same circuit? Did you plug in your kettle to these other receptacles?

Can you trace the circuit back to the panel? How many other devices are on that circuit?

I'd start by verifying I had a well bonded water line. Then I'd investigate the circuit back to the source. Electrical troubleshooting is a process of elimination.

 

[dyqik]

Is it possible that ground and neutral are reversed going into the GFCI outlet? That would explain a couple of volts from outlet ground to the water pipes, and why the GFCI doesn't trip (current is returning to the GFCI outlet's neutral, but getting sent from the GFCI to the ground).