Electric Shock from bad water heater element

[evolvingpowercat]

One comment on my prior post - I forgot about the fact that most modern digital volt meters don't put enough load between the camper frame and ground rod to dissipate stray voltage caused by electromagnetic fields in the world around us. These may cause a measurable stray voltage but can't produce enough current to feel or do harm. Here is an updated diagram if you read a voltage and want to see if it is harmless. Put a 10,000 ohm resistor between the same two places you connected your AC meter. This is simulating the kind of load that a person with dry skin would put between the RV and the ground so the voltage you read with this resistor there is what is important to know and deal with if it is over 0.3 volts AC.

 

[kakampers]

WOW, Randy...thanks for this great detailed information! Next time we have an electrical issue in our coach, I know exactly who I'm looking up....

 

[RollingHome]

There was/is question about the mechanics of heating element construction. These I suppose are to answer the OP as to how (exactly) this could have happened. There was also discussion how/why the anode fits in. Here is how most are constructed. There are various attachments to the device (water heater) some screw in, some have a flanged bolt pad and some are integral to the unit being heated. The point is, they are attached and provide an excellent path to ground for stray voltage “IF” the ground is good. Past the attachment is what is commonly called a calrod. This is a generic name for the following. The elements have 2 conductors, hot & neutral (black & white). The wires attach with nuts or screws. The calrod is actually a case (conduit) usually made of metal or ceramic. Inside the calrod is nickel chromium wire commonly known as Ni-chrome wire. This Ni-Chrome wire is what heats the water when voltage is applied. Immediately surrounding the Ni-Chrome wire is silicon sand – just like white beach sand. The sand insulates the Ni-Chrome wire from the outer case and prevents burn through because it takes about 3000 F to melt it. This is basically how all heating elements are constructed. This is the general construction whether they are in your electric baking oven, water heater or other device.

If the anode is not replaced and is eaten up, the next thing to dissolve is usually the heating element. This is why it is important to replace the anode yearly.

 

[JohnDar]

Thanks for the info on the element construction, Tom, I was interested in it. But, it sounds like one of the first levels of prevention is regular inspection/replacement of the anode rod. For those of us that winterize our rigs, it's necessarily part of the process. I would wager that most of us don't even think about the condition of the element until it stops working. From strictly a curiosity standpoint (used to do a fair amount of failure analysis), I'd like to know what the OP's heating element looks like, but thoroughly understand they would not be of a mind to satisfy that curiosity.

Also glad they were only shocked, albeit seriously, and not electrocuted.

 

[evolvingpowercat]

> This all fun academic stuff. The real concern remains why did the water heater element pass current to the frame of the trailer and almost electrocute some people. If this is a possibility as rigs age, what is the preventative measure to guard against it?

Preventative measures:

Electric Hot Water Heater on a GFCI protected circuilt. The trailer electrical box may take GFCi breakers if so the breaker in the RV could be replaced with a GFCI type one. Or the whole trailer could be protected with a GFCI equipped surge supressor in line with the power cord or the kind that is permanently hard wired in the travel trailer. These solutions have the advantage of working anywhere you are, on either a generator or shore powered outlet.

 

[jimtoo]

There has been lots of great information posted here about preventive measures, checking procedures and remedies. But I would like more information from the OP.

The OP posted, "Last week we had the unit plugged in at home & we weregetting ready to head out for the 4[SUP]th[/SUP] of July weekend."..

My questions are:

Is the trailer normally stored at home where it was located at the time this happened?
Was the trailer plugged into a 15 amp, 20 amp, 30 amp, or 50 amp circuit?
What kind of cord was used,, regular one that came with trailer,, or some other type of extension cord?
Was the water hooked up and turned on? Was the water heater full of water?
Did the water heater work on electric the last time it was used?
After the event happened, was the trailer unplugged and then plugged in again when the checking was started?
The 110v that was measured,,,was it from trailer body or frame to ground or how and where was it measured?

I think we need some answers from the person or tech that did the checking and determined what was causing the problem.

Jim M

 

[porthole]

If it looks like a************ .............................

Still only one post.

If you want to know what the comment that was censored out was (unnecessarily so) - pm me

 

[katkens]

If it looks like a**************...........................

Think I have to agree , poster has been back on with no further comments.......

 

[jmsokol]

I'm the author of the No~Shock~Zone website (www.noshockzone.org) and have experimented and written extensively about hot-skin conditions on RVs. Unfortunatley, a lot of what's already been answered on this thread is hearsay and old-wives tales, and much of it untrue. I've written a 12 part article there which is also posted on www.RVtravel.com about how electricity works and how to test for dangerous conditions.

Here's how the electrical grounding system on an RV really works.

All modern (and correctly wired) RVs will have a safety ground wire in their shore power power plug. This is the little U-shaped or round pin on your power plug. This ground pin needs to be "bonded" to the frame of your RV (inside your power panel) so that it provides a low-impedance (short-circuit) path from the RV's frame/skin to the ground-bonding point in the incoming electrical service panel. It's job is two-fold... first it's there to drain off any small leakage currents inside your RV from appliances. It's also there to trip the circuit breaker if you pinch a wire in a box, creating a direct short to the appliance or RV chassis. Int the first instance, these leakage currents can be caused by an aging microwave with its power transformer insulation degraded by heat and vibration, or a pin-hole leak in the heating element of the hot-water heater (sounds like what happened to you). Now, for the safety ground wire of your RV to actually do its job, it must be connected to a properly grounded/bonded power outlet. That way there's a complete circut path from the electrically leaking appliance back to the service panel, where that current will short out at the panel's bonding point, which is where the Neurtal, Ground and Ground rod are all supposed to meet (bond). This works well in principal, but ALL RV's (no matter what the age or brand) can have a hot-skin condition caused by plugging into an incorrectly wired power outlet. The most common failure in a house or garage outlet is that the ground connection is open (broken). This condition allows the chassis and skin of the RV to go to whatever voltage it feels like, which can vary from close to zero (no appliance electrical leakage) to 120 volts (fully energized ground pin). Usually it drifts to around 60 volts AC or so. Here's a video of me electrifying a 40 ft RV with various voltages and testing for a hot-skin condtion: http://www.youtube.com/watch?v=Y8h64X33aKg&feature=plcp

Now not withstanding the previous post about 3 volts being dangerous, I suspect he meant 30 volts as that's the generally accepted minimun electrocution voltage. However, one brief word about using the word "electrocution". To say that you're "electrocuted" actually means you were killed by electrical voltage. You can be "shocked" and not killed, but you can't be "electrocuted" and still be alive.

So I believe that your real problem is an improperly wired electrical outlet in your garage. It most likely has an open ground, which allowed the internal electrical leakage of your hot water heat to bias the chassis/skin of your RV to 110 volts. Fixing your hot-water heater element without correcting the wiring problem in your garage outlet will set you up for a repeat of this terrible event in the future. The next time an appliance in your RV developes some electrical leakage (could be your fridge or microwave next time) your RV chassis/skin will go back up to the line voltage. So have the outlet checked to proper ground immediaty, before plugging anything else into it.

There's also an extremely dangerous outlet condition which I've deemed an RPBG (Reverse Polarity Bootleg Ground). This often occurs when an older house or garage has been "upgraded" to grounded outlets. See http://www.rvdoctor.com/2001/07/friends-of-gary-mike.html for the article I just wrote about this condition on Gary Bunzer's RV Doctor newsletter. An RPBG outlet can't be detected with a 3-light tester (like shown in a previous response), nor can it be detected using a $300 Ground Impedance tester such as an Amprobe INSP-3. You can't even detect it using a volt-meter between Hot-Ground, Hot-Neutral and Neutral-Ground. Everything will tell you it's wired properly and your appliances and RV will appear to operate correctly. However, it will induce a full 120 Volts AC with 50 amp current potential on the frame and skin of your RV. The ONLY way to detect this condition is to either measure from the chassis of the RV to a metal rod driven in the ground (lots of work) or use a non-contact AC test like a Fluke VoltAlert ($25 and easy to do). See http://www.youtube.com/watch?v=iLk-6pvSlWg&feature=plcp for a video where I demonstrate how 3-light testers and ground impedance testers fail to find a RPBG outlet, and how to test for this condition with a NCVT (Non Contact Voltage Tester) such as a Fluke VoltAlert. Here's a video of me testing a small scale RV model for hot-skin condtions: http://www.youtube.com/watch?v=rtT3te_XNBM&feature=plcp and an printable article on the subject as well: http://www.noshockzone.org/rv-electrical-safety-part-iv-–-hot-skin/

Please have your electrician contact me about thesting since I believe he missed the fact that your garage outlet either has an open ground, or an Reverse Polarity Bootleg Ground. And feel free to contact me directly about how to avoild getting shocked from an RV. You were very lucky that nobody was killed, and I've received hundreds of similar emails from around the country about similar events, some of which resulted in death. ANY outlet you plug your RV into should be checked for both voltage and ground conditions, and simply using a $20 NCVT on the skin of your RV right after plugging it into ANY power source will find most (if not all) dangerous hot skin conditions.

Contact me at my email below for clarification of any of this. But be assured, I've done the experiments and published papers about this subject. If anybody ever feels even the slightest electrical tingle from their RV, it could be caused by a failed extention cord, broken dog-bone or pigtail, corroded Ground bonding point in the RV, or a miswired or corroded electrial outlet in your garage, home or campground pedestal. Unplug immediately and have it vetted out from the outlet to the frame of your RV.

Mike Sokol
mike@noshockzone.org
www.noshockzone.org

 

[kakampers]

Mike...I assume my 50 amp Progressive EMS will also detect the RPBG?? I know it detects open grounds...

 

[TedS]

Mike, thank you for the correct advice.

 

[Urban350]

Mike...I assume my 50 amp Progressive EMS will also detect the RPBG?? I know it detects open grounds...

I hope mine works on everything mentioned in this post also.

 

[wdk450]

JMSokol:
Great post on this safety subject. Would you agree with me that one of the weak links in the grounding system might be the power connector to the trailer, that is continually connected and disconnected, thereby causing wear on the connecting surfaces, the internal wires, and loosening the connector wiring screws?

Making the analogy to my hospital electrical safety inspections, bad grounding in power cords was the deficiency we would most often find. Of course, we also tested that the device was still within low electrical leakage specs WITHOUT the ground intact (simulating a broken cord ground).

 

[jmsokol]

Mike...I assume my 50 amp Progressive EMS will also detect the RPBG?? I know it detects open grounds...

No it will not!!! I've actually talked to Progressive and a few other manufacturers about this, and none of their products will recognzie an RPBG outlet with with Hot at earth potential, and the Neutral/Ground at 120 volts. And they don't disconnect the safety ground wire in the shore power plug if they trip. So it's possible to have a RPBG induced hot-skin with all the power in the RV turned off. Turning off the circuite breakers in your RV won't disconnect the hot-skin currents either. And if you have a reflected hot skin caused by the campground's unbonded safety ground, and another RV on your branch circuit leg, even turning off the main circuit breaker on your pedestal won't stop the hot-skin condtion. The only way to find a RPBG on a 120-volt outlet is by comparing it to earth, either by measuring the voltage from the RV frame to a ground rod, or by using a NCVT such as a Fluke VoltAlert.

 

[jmsokol]

JMSokol:
Great post on this safety subject. Would you agree with me that one of the weak links in the grounding system might be the power connector to the trailer, that is continually connected and disconnected, thereby causing wear on the connecting surfaces, the internal wires, and loosening the connector wiring screws?

Making the analogy to my hospital electrical safety inspections, bad grounding in power cords was the deficiency we would most often find. Of course, we also tested that the device was still within low electrical leakage specs WITHOUT the ground intact (simulating a broken cord ground).

Yes, most certainly!!! All connectors are the weak links in the system, as you well know. So the shore power connector should always be inspected for pitting, corrosion, and loose screws.

 

[jmsokol]

I hope mine works on everything mentioned in this post also.

You didn't mentions the brand and model, but I know there's nothing being manufactured currently that will detect and shut off a hot-skin voltage if you're plugged into an RPBG outlet. If any of the manufacturers would like to contact me about it, I'm glad to consult with them on the topic and arrange for a demonstation.

Mike Sokol
mike@noshockzone.org
www.noshockzone.org

 

[Urban350]

It was also the progressive ems, thanks.

 

[jbeletti]

Mike,

Thanks for your feedback on this thread. Not sure if we're going to hear back from the OP but I sure hope they circle back and read the thread they started. If the theory holds that they did have a failed AC water heater element that exhibited with current on the frame/skin caused by an open ground on their electrical supply from their house, I just hope they can get that checked out and repaired as well.

I think this is a good learning thread for all in the sense that it points out that AC power source issues can have odd/dangerous effects on the coach in certain circumstances. And of course, this is not limited to power sources at our homes, but also at RV parks. I've heard all kinds of stories from our members about CG power issues, some of which caused issues with equipment in their coaches.

Maybe we all need to look closer at 30 and 50 amp RV receptacle testers that can test for all perils.

Jim

 

[JohnDar]

...Maybe we all need to look closer at 30 and 50 amp RV receptacle testers that can test for all perils.

Jim

Does such a device exist? If anyone has a lead on it, please post the link.

 

[jmsokol]

I got buzzed yesterday while crawling around under the trailer on the damp ground. Called a few smart people and I have verified that my feed coming into the well house is only a 3-wire. The RV service is wired correctly with a 4-wire conductor. I will be installing a ground rod to the neutral lug in the breaker box this weekend. the first couple times were just a tingle then a couple were more of a jolt, like an electric fence. We determined it was a problem with the shore power because it didnt do the same thing on generator power. It stopped as soon as I disconnected the shore power.

Actually, a separate ground rod won't fix it... and unless it's bonded to the incoming service box's groud/neutral/ground-rod's bonding point, is a serious code violation. The reason for this is simple.... the earth is actually a pretty poor ground. Even a properly intalled ground rod will have something like 25 ohms impedance to earth, and could be up to 100 ohms in dry soil. The ground rod at your electrical service panel is there to drain away lightning-strike voltage, not provide a return path for fault currents in the branch circuits. You need to run a safety ground wire from the ground screw of your outlet back to your service panel's ground-bus. The service panel bond point creates a ground-plane that's CLOSE to earth ground (maybe only by a volt or two), but it's not supposed to be the fault current path, so it's a code violation to use a separate ground rod, not matter how convenient it might be.

Now, a ground rod may appear to fix a high-impedance leakage from something like a microwave's transformer being old. But it probably won't be able to drain off the charge from a pin-hole leak in a hot water heater element, and it certainly will do nothing to trip the circuit breaker in your RV or outlet if you pinch a hot wire under a bolt or box lid. In that case, it may happily send 5 or 6 amps to the earth (120 volts divided by 20 ohms equals 6 amps) which is not enough to trip a 20 or 30 amp circuit breaker. That's why the code requires all ground wires be directly connected back to the service entrance panel.

Mike Sokol