Electric shock through screen door

[ITSNO60]

Think of it this way, in order to clear a ground fault, current flow must increase high enough to trip a circuit breaker (or melt a fuse). In order for this to happen, there needs to be a good path back to the transformer's center tap for many electrons to flow quickly (ie: a complete circuit). The main neutral, or the grounded conductor as it is properly referred to in the NEC because it is solidly grounded to the center tap, is a superhighway back to the transformer. The current races back to the transformer in the thousands of amps. tripping the breaker immediately before someone gets hurt, or worse.
On the other hand, the earth is a very poor conductor, think of it as primitive trails for the electrons to navigate. While some electrons will travel through the earth over to the ground rod at the transformer (electricity takes all paths) and make their way to the center tap, there will not be enough to increase the current substantially to trip the breaker. The grounding system will simply remain energized and will add to the available surface area of energized metal that can shock you. The electrons will sit there like a big traffic jam. Now bring in the main bond at the service, it is like an "on ramp" for the electrons. Since the resistance is much lower than the earth most of them will jump onto the superhighway and race back to the center tap, tripping the breaker.

A huge common myth is that electricity "returns to the earth". Electricity returns to it's source, all of it. If it didn't, there would not be a circuit and the electricity would not work.

[Al and Missy]

Originally Posted by ITSNO60

Earth grounding at the levels of voltage being discussed here by the use of ground rods etc. does nothing to mitigate a ground fault, as Mollysdad points out with his ground rod experiment, the earth's resistance is too great to carry enough current to do anything, let alone trip a circuit breaker. In the case of an uncleared fault the ground rod and everything connected to it simply becomes energized, a very dangerous situation. Ground rods were never intended to clear faults in household systems. That would be the job of the grounded conductor, or the neutral as some call it. The grounded conductor, not to be confused with the grounding conductor, is solidly connected to the center tap of the transformer. When a ground fault occurs, current travels along the grounding system back to the main disconnect where the grounding system is bonded to the grounded, or neutral conductor. This allows massive current to flow which in turn overloads the over current protective device (circuit breaker) causing it to open, which removes the ground fault.

Grounding is a largely confusing and mis-understood subject, even by many "electricians". Anyone who has a firm understanding of Ohm's law can see how a ground rod is useless at clearing faults of household voltage levels. The ground rods at your house are there for lightning and for faults on the grid caused by transmission lines contacting secondary lines.

A ground rod at the trailer sets the potential of the trailer (whatever that is) to the potential of the ground near the rod. This does not clear any ground fault but reduces the potential for personnel shock. As previously mentioned, in the absence of a good connection between the trailer ground system (everything connected to the trailer green wire network) and the neutral to ground bond in the distribution panel at the campground or home, filters in appliances like Televisions and Converters can cause a potential of 60 volts or so (at a very low current) to exist on the trailer green wire ground.

Al

[ITSNO60]

Originally Posted by Al and Missy

A ground rod at the trailer sets the potential of the trailer (whatever that is) to the potential of the ground near the rod. This does not clear any ground fault but reduces the potential for personnel shock. As previously mentioned, in the absence of a good connection between the trailer ground system (everything connected to the trailer green wire network) and the neutral to ground bond in the distribution panel at the campground or home, filters in appliances like Televisions and Converters can cause a potential of 60 volts or so (at a very low current) to exist on the trailer green wire ground.

Al

Yes I agree to some extent but setting up equipotential bonding in this case would be putting a band aid on instead of getting to the root of the issue. Also due to the resistance of the earth there will likely still be an unequal potential existing unless one is standing directly on the ground rod in bare feet. Equipotential bonding is normally used to bond adjacent metal surfaces to eliminate the potential between them, trying to bring a spot of earth to the same potential as a metal object would not work so well.

[TG Twinkie]

I was referring to the coach distribution panel. Which is considered a "sub" panel.

[ITSNO60]

Originally Posted by TG Twinkie

I was referring to the coach distribution panel. Which is considered a "sub" panel.

I assumed you were but I wanted to make it clear to others reading this thread.

[paddle whisp]

I'd be hooking that camper up and headed straight to the dealership it came from....
Or Ohio to the airstream factory
Don't mess up your warranty

[azeeb]

Originally Posted by uncle_bob

Hi
There is indeed another possibility - grandpa's house may not be grounded properly (yikes !!). You can have the whole house wired up so in the house "ground is all the same". You will not quickly notice any issues. The connection from what the house calls ground to the "earth outside" may or may not be a solid one. All will seem ok, but it's not. Yes, that's the abridged version, there are a few other boring details. It might well be worth having an electrician stop by and take a look.

Bob

I think this was probably the case. We were plugged into a detached garage just off the house. In retrospect, I'm not sure if the garage even had it's own sub panel and ground rod, or if everything was wired back into the house. The house is 70-80 years old. I only noticed the issue with my bare feet on the ground and touching the screen door. Even then it was a pretty small tingle.

We haven't had any issues at the campground we are at now, and everything tests correct at the pedestal and at the outlets inside the trailer.

[ITSNO60]

Originally Posted by azeeb

I think this was probably the case. We were plugged into a detached garage just off the house. In retrospect, I'm not sure if the garage even had it's own sub panel and ground rod, or if everything was wired back into the house. The house is 70-80 years old. I only noticed the issue with my bare feet on the ground and touching the screen door. Even then it was a pretty small tingle.

We haven't had any issues at the campground we are at now, and everything tests correct at the pedestal and at the outlets inside the trailer.

This could happen with a compromised neutral in combination with a neutral/grounding bond. The return current meets up with higher resistance on it's way back to the source and some of it divides onto the grounding system.

[uncle_bob]

Originally Posted by azeeb

I think this was probably the case. We were plugged into a detached garage just off the house. In retrospect, I'm not sure if the garage even had it's own sub panel and ground rod, or if everything was wired back into the house. The house is 70-80 years old. I only noticed the issue with my bare feet on the ground and touching the screen door. Even then it was a pretty small tingle.

We haven't had any issues at the campground we are at now, and everything tests correct at the pedestal and at the outlets inside the trailer.

Hi

We are in the middle of getting grandma's house "up to code" so it can be sold. It's been "improved" many times over the last 70+ years. I'd bet that none of it was done by somebody with a proper license. Every visit for the last 40+ years has involved at least a day's work on one or another issue ....

So yes, I very much understand what may be lurking in an 80 year old house and it's wiring. It's worth having it looked at.

Bob

[Voltair]

Gosh, electrons flowing on this Post.Reminds me off another posting by some very intelligent Old Burt's on discussing vapor locks in Airstream fuel systems, that was worthy off being a Monty Python skit, but this is not... while arguing the toss back n forth sitting in your trailer's your neighbors child runs up the door in bare feet wondering what all the funny commotion inside is all about and under ideal condition well.....
I build products that use very large voltages - amperage both AC/DC, after all the installations are done by experts, I personally drive in a 8ft copper ground rod with proper connections directly back to the metal body work off my machines.
Ohms Law: a deep rod into the ground next to my Airstream = lower
potential than the neighbors kid's bare feet.
Connection:a suitable unbroken DC flexable battery cable from engine to body frame to chasis to bolted connection on the rod in the ground. In the END a very cheap insurance against Lightning strikes,spiralis voltage from any electrical breakdowns to static electrical feilds that will cause fili form damage to thoes shinny alloy skins. Dont forget to unbolt befor you drive away thoe.

Rus

[Glenritas]

Grandma's 70 -80 year old house may still have knob and tube wiring . The house may be only a 2 wire system and somewhere in the system the hot and neutral wiring may have been reversed at a fixture or in an appliance .

So the rest can be scary thus the tingle.

[uncle_bob]

Originally Posted by Glenritas

Grandma's 70 -80 year old house may still have knob and tube wiring . The house may be only a 2 wire system and somewhere in the system the hot and neutral wiring may have been reversed at a fixture or in an appliance .

So the rest can be scary thus the tingle.

Hi

Even more fun ... exposed knob and tube. At least that way you *know* what you are dealing with. I've spent a lot of time ripping that stuff out and replacing it. The "tingle" issue sometimes is the least of the hazards .... That's why a check is well worth the effort. The problem the guy finds may be much more significant than a simple ground potential difference.

Bob

[Re-Pete]

Originally Posted by azeeb

I think this was probably the case. We were plugged into a detached garage just off the house. In retrospect, I'm not sure if the garage even had it's own sub panel and ground rod, or if everything was wired back into the house. The house is 70-80 years old. I only noticed the issue with my bare feet on the ground and touching the screen door. Even then it was a pretty small tingle.

We haven't had any issues at the campground we are at now, and everything tests correct at the pedestal and at the outlets inside the trailer.

azeeb,
I.had a very similar experience about 5 years ago. While visiting a friend living in an older home, which she rented, I plugged into a grounded outlet in the basement where she had her washing machine plugged in.

Latter walking around the back of my AS I touched my bumper and got quite a tingle. I had checked the outlet with my voltage meter before plugging in and it was fine, but I hadn't checked the power to ground. Surprise,l there wasn't one. Someone had simply replaced the original two prong outlet at some point with a three prong outlet, but they did it on an ungrounded circuit. So, that hole for the ground prong was totally valueless, not to mention dangerous.

Since our friend had her washer plugged in there, on a concrete floor I warned her to call her landlord to fix it. I'm not sure she did, but for me it was a lesson learned, never trust anything in an unfamiliar house, especially if it's older.

I know that's what it was because I've been more careful since and have not had a repeat experience. Not day you shouldn't verify, but I'm sure your camper is fine.

Safe travels,

Pete

[Mollysdad]

Life is full of surprises.
I don't want to repeat the one I got when crossing the electric fence while standing in a puddle. The barbed wire pierced my jeans. I only did that once.

[GandW]

From 40 years of experience, This could also be a utility company problem. If they have a poor neutral connection at their transformer, but their ground is good, the return will be split between neutral and ground. Most of the current will return on the neutral, because it is still the better conductor. Less will return though the ground, because it has a higher resistance.

I had a neighbor that was afraid to wash clothes in her bare feet. When she touched the washer, even with it off, she was shocked. Electricity will do some mind stretching things!

[streaminwild]

Originally Posted by Mollysdad

I don't want to repeat the one I got when crossing the electric fence while standing in a puddle. The barbed wire pierced my jeans. I only did that once.

I'm into this kind of pain...so once is not enough.

[MelGoddard]

Originally Posted by streaminwild

I'm into this kind of pain...so once is not enough.

YER WIERD!!

[Jammer]

Originally Posted by azeeb

A few weeks ago I remember seeing a thread from somebody about feeling a slight electric shock through the screen door. ... I tested things a bit and it seemed to go away when the radio was turned off. I am plugged into a 15 amp circuit at my wife's grandpas house. The circuit tests correct with my plug in tester.

Has anyone else had this problem and figured out how to fix it? Now I can't reproduce it, so it seems intermittent. When I get a chance I'm going to pull the stereo and look for a loose connection.

There are many possible causes, and electrical problems are next to impossible to diagnose over the internet. You've gotta have someone truly qualified looking at the problem, and for intermittent grounding problems, that's going to be a hard individual to find.

That said, my money is on the problem being in the house rather than the trailer. In older houses where some of the wiring was installed by unqualified individuals, it is common to find the neutral and the ground wires connected together deliberately at various points. This can lead to a mild electric shock when contacting something that depends in the ground wire working correctly. Typically the problem will come and go as loads in the house are turned on and off. The three-light outlet testers will not catch this problem.

Good luck