Hot skin issue please help

It's amazing the number of posts on these boards about tripping GFIs that are solved by plugging into a non GFI plug. Wrong answer.

And that's why you need a good safety ground on your RV. A tripping GFCI is a warning that something is leaking electrically inside your RV. Not dangerous just yet, but it could turn very bad in a heartbeat. There are very few GFCI random trips that can't be explained by a Hot-to-Chassis leakage of some appliance or Surge Strip (yes, they leak about 3 mA to ground). If you have a solid ground connected to your RV it will drain any voltage away before it becomes dangerous. But if you don't have a solid ground, then an RV hot-skin condition can exist with any appliance leakage to its chassis.

Under no circumstance should you ever measure more than a volt or two between the earth ground and your RV chassis. If you do, then you don't have a low-impedance connection back to the ground bonding point in the incoming power service panel. Seems like a simple concept, but often missed by both DIY and professional electricians.

And no, putting your jacks down on the dirt is definitely NOT a safety ground.

Mike Sokol

NJRVer wrote:
Mike, keep up the good work!

From what I remember the element was split open about a 1/2".

Yup... I've snagged a couple of burned out hot water heater elements for this experiment. Interestingly, in a home (240-volt) situation, the thermostat only opens up one of the two hot legs. So even though the hot water may be up to temp, there will be a continuous leakage of perhaps 2 or 3 amps into the water itself from the "always on" leg, and a steady stream of hydrogen and oxygen ( or chlorine) gas. I'm trying to remember my high-school chemistry, but I think that chlorine and hydrogen gas in the presence of water will create hydrochloric acid. May be the reason why some hot water heater pipes I've looked at appear to be rotted from the inside out. Also may explain why some hot water heaters seem to randomly explode. If there's a 2:1 proportion of hydrogen and oxygen gas in the top of the tank from this electrolysis action of the split heater element, then a spark caused by the broken element itself could ignite a Brown's Gas explosion. No proof of this yet, so I'm proceeding slowly so as not to blow up my garage (or me).

Mike Sokol

enblethen wrote:
No, the ground in the AC system is connected to the metal portion of the rig.
Induced current is what gets into the skin and also leakage from devices getson to the ground of the AC system.

That doesn't sound right; in fact it sounds dangerous.

Never mind I read it wrong; skipped over "ground"

SuwanneeDave wrote:

CA Traveler wrote:
The second apparent problem is a ground fault as indicated by the hot chassis. The new adapter with a good ground can mask a ground fault. Plug the rig into a known good GFI plug and turn various equipment on and off. If the GFI trips then you need to find the ground fault.

Yeah, I am wondering how the current is getting into the skin. Shouldn't the electrical system be isolated from the chassis?

Ideally the hot and neutral wires should be isolated but devices sometimes leak very small amounts of current to ground. GFIs trip when 5ma leakage is detected. Leakage above 5ma is not considered safe. The chassis and skin should be bonded to the power cord ground.

Per above a good ground masks the leakage so plug your RV into a GFI plug periodically to make sure it's OK.

It's amazing the number of posts on these boards about tripping GFIs that are solved by plugging into a non GFI plug. Wrong answer.

No, the ground in the AC system is connected to the metal portion of the rig.
Induced current is what gets into the skin and also leakage from devices getson to the ground of the AC system.

CA Traveler wrote:
The second apparent problem is a ground fault as indicated by the hot chassis. The new adapter with a good ground can mask a ground fault. Plug the rig into a known good GFI plug and turn various equipment on and off. If the GFI trips then you need to find the ground fault.

Yeah, I am wondering how the current is getting into the skin. Shouldn't the electrical system be isolated from the chassis?

Mike, keep up the good work!

From what I remember the element was split open about a 1/2".

NJRVer wrote:
Just to add. We had a hot skin condition that was caused by the electric heating element in the hot water heater.
Hot water heater had been energized by the dealer with no water in it which caused the element to burn out unbeknownst to us.
When the tank was full of water and we turned on the electric element it caused the hot skin.

I've been doing experiments along this line, and there's two pieces of information to consider.

First, if you have a properly grounded RV via the shore power connection, an electric hot water heater element with a pinhole leak WILL NOT cause a hot skin condition to exist. Of course, if you have an open safety ground due to a miswired receptacle, broken power adapter, or open ground in your extension cord, then certainly the electrical leakage in a compromised hot water heater element will instigate the hot-skin condition and can raise the voltage up to 120-volts with approximately 2 amperes of fault current available. This is enough current to trip a GFCI, but not enough to trip a 15 amp circuit breaker. I know this because I'm running a test right now using a rusted-out hot water heater element inside a visible hot water heater tank where I'm testing for hydrogen gas generation.

Secondly, a hot water heater element with a pinhole leak will create a steady stream of hydrogen gas bubbles, and quite possibly a matching stream of oxygen gas. How much oxygen that's created will depend on water chemistry, with high salt content creating chlorine gas and other stuff. The key point is that there will be either HHO (Brown's) gas created, which is highly explosive, or a combination of Hydrogen and some other corrosive gas which can rot out the inside of your hot water tank. I've been collecting a few cubic inches of Hydrogen and ??? gas per hour, so a week's worth of operation without turning on the hot water faucet to purge the gas could fill up your hot water heater with a significant amount of gas. I'm not sure just how explosive or corrosive this gas will be just yet, but that's my next experiment.

I'll be writing articles about this as soon as I gather some useful data.

Mike Sokol

Just to add. We had a hot skin condition that was caused by the electric heating element in the hot water heater.
Hot water heater had been energized by the dealer with no water in it which caused the element to burn out unbeknownst to us.
When the tank was full of water and we turned on the electric element it caused the hot skin.

beemerphile1 wrote:
I very much doubt it is an open ground. Most likely it is a case of reversed polarity. Read this;
http://www.noshockzone.org/rv-electrical-safety-part-iv-%E2%80%93-hot-skin/

Then also read this;
http://www.noshockzone.org/category/rv-safety/

If you read my NoShockZone articles carefully, you'll see that a standard "reversed polarity" (swapped neutral and hot) outlet will NOT cause a hot-skin condition on a properly wired RV with its own neutral and safety ground separated according to NEC and RVIA code.

However, there is one very dangerous outlet condition I've named an RPBG (Reverse Polarity Bootleg Ground) outlet, which sometimes occurs when an old ungrounded outlet is "upgraded" to a grounded outlet by putting a jumper wire between the neutral and ground screws, rather than running a new ground wire. If the incoming hot and neutral wires have been accidentally swapped, then the ground and neutral contacts in the outlet will be at 120-volt above earth ground, while the hot contact will be at earth potential. This creates a condition where the entire skin of the RV has a low-impedance connection to 120-volts, which is the most dangerous hot-skin condition possible. But, crazy as it seems, the entire RV will appear to operate properly even though its wired "upside down". And there's no 3-light tester in the world that will detect an RPBG condition, nor can you measure for it using a voltmeter across H-N, H-G and G-N contacts in the receptacle. The ONLY ways to detect this condition is to measure the trailer skin/chassis voltage to an earth ground (ground rod) or by using a Non Contact Voltage Tester (NCVT) such as a Fluke VoltAlert. Please read my article about RPBG dangers and how to test for them on Gary Bunzer's site (The RV Doctor) at RPBG Outlets

I'm an advocate for everyone testing their RV's for hot-skin conditions using an NCVT which are available anywhere for $20 or so. Typically used by electricians to see if an outlet is "hot", they can be used a a very safe and simple proximity test for an RV hot-skin condition. Watch this video at http://www.youtube.com/watch?v=Y8h64X33aKg where I hot-skin electrify a 40-ft RV and test for it with a Non Contact Voltage Tester.

Mike Sokol
mike@noshockzone.org