# Shock while touching garage metal switch box



## clydesdale (Nov 25, 2010)

diykatz said:


> I just noticed a mild shock while touching the metal light switch box in the garage. The switch is probably 20 yrs. old or so. Should I suspect a defective switch?
> 
> I took a look at the metal box under our meter where the main breaker to the house. The ground rod protrudes above the ground, maybe 8" or so. The connection is very corroded.
> 
> ...


I will let the pros jump in on this one but if all of the sudden every outlet is reading hot and neutral reversed you may have an open neutral somewhere which is a dangerous situation. The ground rod is there for lightning protection so I would not go any further down that path at this time. I would unplug any electronics in the house as an open neutral can cause damage. Call an electrician.


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## diykatz (Sep 6, 2011)

Hi clydesdale,

Thanks for that info. I'm not actually sure that the "hot and neutral reversed" reading is an accurate one. After I got that reading, I searched the net & found that it can be an inaccurate reading with these plug in type testers. Hopefully I gave enough correct info. in my initial post. In regards to your statement -


> all of the sudden every outlet is reading hot and neutral reversed


I'm not really sure if this is the case, as in "all of a sudden". This may be a condition that has been like this forever & I didn't realize it. That's why I am suspecting an erroneous reading in this case.


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## clydesdale (Nov 25, 2010)

diykatz said:


> Hi clydesdale,
> 
> Thanks for that info. I'm not actually sure that the "hot and neutral reversed" reading is an accurate one. After I got that reading, I searched the net & found that it can be an inaccurate reading with these plug in type testers. Hopefully I gave enough correct info. in my initial post. In regards to your statement -
> 
> I'm not really sure if this is the case, as in "all of a sudden". This may be a condition that has been like this forever & I didn't realize it. That's why I am suspecting an erroneous reading in this case.


When was the house built? What type of wiring?


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## kbsparky (Sep 11, 2008)

Is this a detached garage?

Older installations may not have required separated neutral and ground wires. If there was a 3-wire feeder, this may be a possibility.

IF this is the case, your metal boxes and enclosures may be physically connected to your neutral conductor, which is a current-carrying conductor.

This can result in potential differences between those enclosures and the ground. In other words, touching the metal box, switch plate, or other grounded surface while standing on the dirt, or other grounded surface can cause one to feel that potential difference --> get shocked.

There are other scenarios which can be more lethal than this one, discussed elsewhere in this thread.


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## diykatz (Sep 6, 2011)

This house was built in 1982. It is actually a double wide on a block foundation, which is the garage/basement. I've only noticed this "shocking" scenario a couple of days ago. There has not been any new wiring or anything added for several years. Whatever is causing this is a reletavilty new occurrence. Something has gone "wrong" just recently.

I'm just needing some advise on what to look for as far offending item goes. That is why I mentioned the corroded ground rod connection. It would seem to me that with a faulty ground, electricity could be backfeeding and energizing that metal switchbox. There are other metal boxes in the garage, but after the initial shock (which isn't all that strong, really) I've been hesitant to touch any of the others.


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## clydesdale (Nov 25, 2010)

diykatz said:


> I'm just needing some advise on what to look for as far offending item goes. That is why I mentioned the corroded ground rod connection. It would seem to me that with a faulty ground, electricity could be backfeeding and energizing that metal switchbox. There are other metal boxes in the garage, but after the initial shock (which isn't all that strong, really) I've been hesitant to touch any of the others.


It is not the ground rod causing the problem. If you are going to start troubleshooting you will need a digital multimeter (DMM). Do you have one?


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## diykatz (Sep 6, 2011)

Yes, I have a DMM. How do you suggest I go about testing?


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## Speedy Petey (Feb 1, 2004)

diykatz said:


> That is why I mentioned the corroded ground rod connection. It would seem to me that with a faulty ground, electricity could be backfeeding and energizing that metal switchbox.


Like clydesdale said, the ground rod has nothing to do with this. In fact you could disconnect the ground rod wire and NOTHING would change. 
Grounding electrodes (rods) have nothing to do with the functionality of the circuits in the house. 

Begin by turning off circuits and testing the problem area. Get an extension cord and plug it into a known properly working receptacle. Test from the box to the ground pin and see which circuit make the problem go away.

I must say, I get the impression that having and electrician come out and check this, and everything else for that matter, would definitely be in your best interest.


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## clydesdale (Nov 25, 2010)

diykatz said:


> Yes, I have a DMM. How do you suggest I go about testing?


I would start with some basic voltage readings - take them at a few different outlets inside and at the box where you are getting shocked.

Hot to Neutral
Hot to Ground
Neutral to Ground


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## Billy_Bob (Sep 11, 2008)

"Grounds" in a house all connect together!

With that said, a malfunctioning freezer could have a "leak" or "short" to its metal case, then that electricity is traveling out on the 3rd prong (grounding prong) to everything else in the house which is grounded. That would include appliances with metal cases and 3 prong plugs, dryers, ranges, heating/Air conditioning units, electric water heater, and metal electrical boxes like for your switch.

All those things *should* be properly grounded, but things aren't always installed like they should be.

Anyway I would turn off the main power to the house, then peek inside that switch. Maybe post pictures here of what the outside of the switch looks like, then another with the cover removed, and the switch pulled out a bit so we can see the wiring inside. (Turn off main power to house before doing this of course.)

Then if there are no problems there, turn the power back on and use a multimeter from the metal case of that switch to the ground rod (use a long wire - speaker wire or whatever will do fine for this test). It should measure some AC voltage. Of course DO NOT touch the metal case or the wire to the ground rod while doing this test. Best to use "alligator test leads" to connect the multimeter to the wire/ground rod and metal case, then you can just look at the readings and not need to touch anything.

Next turn off one breaker at a time in your breaker panel. If the problem is coming from an appliance somewhere else, then turning off the breaker for that appliance will make the voltage go away. Then check out whatever is on that circuit.

This can get more complex than this, but that would be a good start. If you are not comfortable doing this, call an electrician. And DO have that ground rod properly repaired.

Alligator clip test leads...


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## Billy_Bob (Sep 11, 2008)

P.S. Warn everyone in the house to not touch the metal cases of any electrical appliances in bare feet nor any metal electrical boxes or a metal garage door if it has an electric opener, until this issue is resolved.


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## mpoulton (Jul 23, 2009)

Shocks from grounded objects and a hot-neutral reverse indication on the tester suggest a situation: Your main panel may not have the grounding system bonded to the utility neutral, and there may be a ground fault somewhere. This is quite a dangerous scenario - ALL "grounded" metal objects in the house would be electrified, including the ground rod itself, and possibly including the plumbing system.


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## frenchelectrican (Apr 12, 2006)

And also let me add this part that if you have city water in your place check the bonding jumper to make sure it is not corroded at all if that happend you have major issue and whatever you do with it is do NOT ever unhook the ground wire or bonding jumper some case it may have some current running thru.

There are some situation it will be best have electrician to find the issue and get this fixed properly.

Merci,
Marc


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## Stubbie (Jan 7, 2007)

> I just noticed a mild shock while touching the metal light switch box in the garage. The switch is probably 20 yrs. old or so. Should I suspect a defective switch?


Could be .. you could replace it for a few dollars. But don't touch the metal box it sits in till you make sure you have resolved the shock issue.



> I took a look at the metal box under our meter where the main breaker to the house. The ground rod protrudes above the ground, maybe 8" or so. The connection is very corroded


.

As said that is not your problem but the connection should be repaired if it is badly corroded.



> Could this be a possible source of the problem?


Nope it isn't your problem but it does need to be repaired.



> Also, I used one of those Ideal receptacle testers, and it displayed all the circuits in the house as "hot & neutral reversed." I'm wondering if this is a false reading, maybe due to a bad ground as I mentioned earlier?


The *earth* ground has nothing to do with it unless you have some very unlikely circumstances. I would not consider it until some other tests are made. Hot neutral reverse is possible. Best thing you can do *first* is turn off the circuit in question at the breaker box and check the wiring for any possible ground faults to a hot wire. You will need to make sure the metal switch box is not hot even after you turn the breaker off. 

You have made a few comments that would lend me to think that an experienced person should diagnose this shock your getting. An energized ground can be life threatning so whatever you do make sure you understand the seriousness and use common sense.


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## diykatz (Sep 6, 2011)

Found the problem circuit; 

When the water heater breaker is switched in, I get the hot & neutral reversed condition. At that time, I read 120 across the two flat terms & approx. 50 across the right spade & ground terminal. When I switch this breaker off, I have 120 across the two flat terms & 120 across the right spade & ground terminal.

So, now to diagnose what is going on in that circuit...


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## Billy_Bob (Sep 11, 2008)

I assume that is a double breaker for the water heater? (240 volts)

In any case, turn off the breaker to the water heater. (Better yet is to turn off power to the entire house.) Then with an ohm meter, measure ohms or resistance from each electrical connection on the water heater to its metal case and/or to the ground wire connecting to the water heater. There should be two "hots" and a ground wire if 240 volts. So measure from one hot to ground. And then from the other hot to ground.

And there should be INFINATE ohms (no continuity - no electrical connection whatsoever) from either of those hot wires to the water heater ground!

Additional testing is required beyond this. Water heaters usually have two elements. These are switched on one at a time. So those might not be connected to the main wiring connections if the water heater is warm enough and the thermostat has turned off, or if on, only one of the elements would be connected to the wiring.

Each element should be behind its own door. Remove each door and check the ohms between each connection and ground. Again there should be NO continuity! See "Test 2" on the following page...
http://waterheatertimer.org/How-to-test-water-heater-element.html

Have your electric bills been higher than usual?

If you are not comfortable doing this testing, call an electrician.


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## diykatz (Sep 6, 2011)

Thanks Billy,

I will test that today. We already switched it off. It is a double breaker. I seem to recall replacing an element, maybe five yrs. ago...

I am comfortable doing those tests, no problem. The electric bills have not been "higher than usual", but too high for my liking, lol. 

We still use about the same KW daily as we have for the past several years, according to the graph chart that the elect. co. provides on their website.


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## mpoulton (Jul 23, 2009)

Water heater ground fault, combined with no neutral-ground bond at the service. The water heater's fault is electrifying your plumbing and your grounding system.


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## diykatz (Sep 6, 2011)

Found the culprit. According to the test performed in the link that Billy provided, the upper element is shorted from the element terminals to the base of the element & also to ground. Now to pull & replace element. Yay! Looks like I will get away with an easy fix this time.


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## mpoulton (Jul 23, 2009)

You still have a bonding issue that you need to solve! Your equipment grounding system is not bonded to neutral in your main panel. If it were, the breaker would have tripped immediately and there would have been no hazard. Unless you fix that, it's just a matter of time until another ground fault somewhere electrifies your grounding system again.


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## diykatz (Sep 6, 2011)

mpoulton,

Should the neutral/ground be bonded at the service disconnect only? That is, my outside mains, which is located under the meter. I have been reading conflicting info. on the net about whether to also bond at the home's inside panel.

Also, In lieu of a crossover bar, I suppose I can simply use a length of insulated wire the same size as the incoming supply wire & connect it on the neutral & ground bars using a lug?


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## RWolff (Jan 27, 2013)

Sounds to me like you were lucky the floor wasn't wet or something, you only got a mild shock because you were not really, fully grounded- you had shoes on, it sounds like if you put a volt meter between that switch plate and a real good ground I'll bet you'll see it read the full 120 volts.

Over the years I have gotten such minor minor shocks, they fell like what I would imagine might be 60 volts or less. It can be the box is energized by a wire that is touching it or a screw terminal that is, and the ground is not there which is why the breaker isn't blowing.

I have seen this in conduit, where a damaged hot wire was in contact with the metal conduit, and the conduit was not grounded. Soon as the conduit had a ground connection on it in the circuit breaker box, the breaker flipped off.


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## mpoulton (Jul 23, 2009)

diykatz said:


> mpoulton,
> 
> Should the neutral/ground be bonded at the service disconnect only? That is, my outside mains, which is located under the meter. I have been reading conflicting info. on the net about whether to also bond at the home's inside panel.
> 
> Also, In lieu of a crossover bar, I suppose I can simply use a length of insulated wire the same size as the incoming supply wire & connect it on the neutral & ground bars using a lug?


Bonding at the service disconnect only. You can use a wire jumper instead of a bonding screw, assuming it fits.


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## diykatz (Sep 6, 2011)

mpoulton/others,

I finally had a chance to look this over, as I've been out of town. I realize I need to run another wire (fourth wire) from the main service disconnect into my house panel in order to bond them. As it stands now I only have the two hots (black) & one white from the service disconnect into the house.

As outlined in the diagram, I need another wire. Also, the water heater is plumbed with cpvc so there is no ground connection to the pipes. Do I need to address that in any way?


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## diykatz (Sep 6, 2011)

<bump>

Any input on this? 
Also, the water heater is plumbed with cpvc so there is no ground connection to the pipes. Do I need to address that in any way? Does the water heater need to have some type of ground to earth?


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## Billy_Bob (Sep 11, 2008)

A water heater with plastic plumbing only needs the ground wire from the power wire connected to its ground connection.

So far as the other trouble, I would turn off the main breaker / switch, then measure the resistance from the ground connection on the water heater to the neutral bar in your main disconnect. Get the reading in ohms. And also measure from the ground connection on the water heater to the ground bar in your main disconnect. Post the results here.

You will need a long length of wire to do this test (cheap speaker wire or whatever will do for the test). And that wire will have resistance (ohms) for the length you are using. Subtract that from your readings, then you will be left with the resistance of the house wiring/connections only.

You also may want to measure the resistance from the ground bar in the service panel to the ground rod outside. To the rod itself, not the wire connecting to it or the clamp, to the rod going into the ground.

These tests will determine if you have good ground connections from the water heater ground all the way back to the neutral bar or if there is a poor connection along the way somewhere.

Several wires / connections to all this...
Wire from water heater to service panel.
Wire from service panel ground bar to disconnect ground bar.
The bonded to box connections from the disconnect ground bar to the disconnect neutral bar.

And the disconnect neutral bar to the ground rod.

Note that even if the main breaker / switch is turned off in the main disconnect, there is STILL live power present! If you are not sure what is live and what is not, then don't do this testing. Also wear gloves and don't touch anything with your bare hands. Best to "assume" various wires are live even though the power is off. Ground and neutral wires can have voltage present from other sources than your house (neighbor's house). Rare, but it happens...


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## mpoulton (Jul 23, 2009)

Whatever metal plumbing you do have must be bonded. The water heater itself needs an equipment grounding conductor.


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## diykatz (Sep 6, 2011)

Billy Bob,

Thanks so much for that lengthy reply. It was late when I made my previous post, & I realize I omitted some info. I no longer have the hot & neutral reversed condition. Replacing the water heater element fixed that. 

At this point all I need to do is run that fourth wire as depicted in the diagram I posted. I was mainly inquiring about a separate ground for the water heater, but you guys have already answered that for me.

The entire house is plumbed in cpvc, so nothing is grounded/bonded to plumbing anywhere. At any rate, all great info. you fellows have posted. It will be good for future reference for others, I am sure. :thumbsup:


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