Shocked by my FWC

[TravelAmateurs]

I know much less than I'd like to about electrical systems so today was an important learning experience.

I pressed my face against the front wall of the camper to check my bumper spacing and felt like something bit me in the cheek. Plenty of bugs in VA this time of year so I didn't think much of it until I felt the same "bite" while grabbing the rear camper door (standing barefoot on the concrete driveway). Reached back towards the door slowly and the buzz confirmed I had been shocked. Unplugged the camper from shore power and stared confused at my soon to be home.

We had plugged into the same extension cord in the past but I realized the camper had always been on blocks on the ground. The camper was now sitting on a rubber mat in the bed of a truck with rubber tires, and I had created a human path for whatever charge was leaking into the frame. We also hadn't run the connection from the truck battery to the camper yet. Would that have mattered?

A little investigating confirmed that the extension cord was connected to an open ground outlet in the shed. Also, while using the open ground extension cord I shoved a big screwdriver into the dirt(for a ground) and tested the camper door with my multimeter to show 49 volts! Another earth ground source resulted in the same reading. Plugged into a properly grounded outlet and the camper door voltage was gone. Any further checks I need to do?

Found this site and the electrical safety series to be a good read for anyone interested:
http://www.noshockzone.org/rv-electrical-safety-part-iv-%E2%80%93-hot-skin/

Also, picked up these two gadgets as I'm sure I'll be plugging into some questionable outlets in the next year or so, and 13+ countries:
Outlet Tester
Non-Contact Voltage Tester

 

[billharr]

Get a GFIC plug for any cord you are using outside. If the camper wiring has problem you will know right a way.

 

[takesiteasy]

Interesting article. Thanks for posting it.

x2 on the GFCI.

 

[TravelAmateurs]

Get a GFIC plug for any cord you are using outside. If the camper wiring has problem you will know right a way.

Thanks Bill. Any suggestions for the type of GFCI plug I would use? After reading up on these systems for the better part of the day I want to be sure I'm getting this right. After plugging into a properly grounded outlet, the AC outlets in the camper tested good.

In most of the articles I've read, the cause of the "hot skin" condition is attributed to a bad or missing ground, improper power plug connection, or bad outlet. I had originally assumed that a voltage leak or wiring problem in the camper was necessary for the current to reach the frame/skin. I'm beginning to think that any camper would have the "hot skin" issue, if plugged in without a ground or an improper plug/connection.

Would any camper become "hot" if using an open ground AC plug or does my FWC have additional issues that I need to diagnose?

 

[Espresso]

My 2001 Grandby wouldn't shock me, but it would blow a GFI at home every time.

 

[jmsokol]

I'm Mike Sokol from The No~Shock~Zone. Thanks for posting links to my blog here. First of all, nearly any RV without a proper ground will tend to bias itself to around 1/2 of line voltage. So for a 120-volt system, that's about 60 volts or so. That doens't imply that anything's wrong with your RV's internal wiring system or appliances. However, it does tell you that your RV has lost its EGC (Equipment Grounding Conductor), more commonly called a safety ground.

While this probably was a relatively high-impedance ground-fault leakage with low fault currents available and not deadly, it can easily turn into a low-impedance, high-current ground fault at any time that will jump up to 120 volts and can easily kill you or a loved one. While it's the current that can kill you, it's the voltage which allows the current to flow. So even 30 to 40 volts AC can be deadly if your hands and feet are wet.

So anytime you read more than just a few volts (maybe up to 3 or 4 volts) between the frame/skin of your RV and an earth ground, that means something has gone very wrong with your grounding system and needs to be corrected immediately. I still think that a standard NCVT (Non Contact Voltage Tester) is the best way to double-check your RV for a hot-skin voltage. Watch my video and feel free to contact me with any questions.

Also, while I do think that a cable GFCI may add an extra layer of protection, they can often nuiscense trip due to additive hot-to-chassis leakage from multiple appliances inside your RV even when nothing is really wrong. For example, a standard surge strip plugged into an outlet in you RV can leak up to 3 mA current to ground and still be UL and code compliante. However, just two surge strips plugged inside of your RV can have more than the 5 or 6 mA (milli-amperes) tripping current.

In any event, any shock should be considered dangerous and corrected immediatly.

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

 

[Stan@FourWheel]

Sounds like there might be a short in the refrigerator 110/120V wiring junction box ?

This junction box is usually located in the back of the kitchen cabinets, on the inside wall of the cabinets, on the other side of the refrigerator cabinet wall divider (under the sink or stove area, depending on sink & stove locations).

I have only heard of this maybe once in the last 13 years. Not sure what else it could be ?

The shop guys said that this is the first place they would check.

The 110/120V electricity wiring is pretty simple and accessable, so I would start poking around and see what you can find.

For around $10 bucks you can get a wire tester at any hardware store or Wal-mart. This might (might?) help you located where or what the possible wiring problem could be.

Hope this helps a little.

Stan




.

 

[craig333]

Thanks for coming on board to explain this condition.

Only about $20 on ebay and amazon. Less if you go offbrand or bid on one from china. I got this one.
http://www.ebay.com/itm/FLUKE-1AC-C2-II-VoltAlert-Non-contact-200-1000V-AC-Ditector-Pen-Voltage-Tester-/251888012111?pt=LH_DefaultDomain_0&hash=item3aa5b20b4f

I rarely plug in to shore power except at home (to charge the batteries) but better safe than sorry.

Now lightning is one we've discussed before so I found this one worth reading.

http://www.noshockzone.org/lightning-safety/

 

[wuck]

GFCI= "Ground Fault Current Interrupter". You had a ground fault, but no interrupter, so you got shocked.

Your camper wiring by itself should not have a path between hot and ground, at least at a low enough impedance (AC current resistance) to cause an issue. However, any electronic device connected will add leakage paths, they are designed in. For instance, an Iota charger/converter, the inverter drive electronics for a refrigerator, or even filtered power strips will all contain capacitors connected between the hot and ground to filter out electrical noise. If the safety ground is secure these are of no consequence. However if the safety ground is bad/absent, and you provide the ground path through your body then you get shocked, or worse. So, as [SIZE=13.63636302948px]Mike Sokol pointed out above, [/SIZE]even if there are no direct shorts present in the wiring you can still get shocked by the lack of a safety ground.

​The little tester Stan attached is great for checking for wiring errors and omissions, they are very cheap insurance. Any and all outdoor outlets at your house/shed should be GFCI protected. This doesn't necessarily mean a GFCI at every outlet, but one at the start of each string or a GFCI breaker can protect the entire path if properly installed. A GFCI plug/cordset will protect you from faulty installations at other places.

 

[TravelAmateurs]

Thanks for the responses. I really appreciate all the input. This is exactly why I love WTW!

Stan - Thanks! I had forgotten about that hidden outlet in the cabinetry so went ahead and tested it with an outlet/wiring tester. When plugged into properly grounded shore power, it tests good. All the outlets show as open ground when I'm plugged into the bad connection from the shed. Also, when I traced all the 110/120 wiring I didn't see any areas of concern.

Mr Mumbles - I'll also rarely be plugged in once I get the solar panels on the roof : ) I have a non-contact voltage tester on the way and will be using that to check the skin/frame and outlets every time I plug in. This also appears to be the best device for identifying a RPBG (Reverse Polarity Bootleg Ground), since an outlet/wiring tester will show as "good." Will be using an outlet tester as well.

Mike & Pat - Thanks for the great info. Seems like any camper/RV with electronics (converter, fridge, etc.) is going to carry some sort of charge if not grounded properly or plugged into faulty wiring/outlets.

The source of my problem was a "2 prong" cord plugged into a non-GFCI outlet in the shed. A surge protector was somehow plugged into this cord, and another "3 prong" cord into that...scary setup caused an open ground. This was a family member's shed but I should have taken the time to check the connection and will do so in the future.

I'd suggest that everyone test their shore power connections. It's very possible that I could have continued to use this bad connection without identifying the issue/danger. When my Hawk was sitting on its jack stands it was grounded, so no shock. When mounted on the truck and I climbed in/out using a plastic stool (off the ground), no shock. Even with shoes on, touching the camper, I wasn't able to feel the shock. BUT barefoot, standing on the ground, and touching the camper I learned that I had a "hot skin" condition the whole time. I also wonder if I was plugged from camper to truck battery, if enough voltage would have drained through the truck to hide the condition (camper is on rubber mat, not touching truck).

Based on feedback it sounds like the faulty ground was the issue, rather than a short in the camper wiring. I was showing 49 volts on the door frame which is less than the 60 Mike mentioned as typical without a safety ground. Thoughts? For reference I have an 05 FWC Hawk (base model options) plus an Isotherm CR-65 fridge (DC only - direct to battery), furnace, and TriMetric TM-2030 RV.

Thanks again everyone!

 

[jmsokol]

Based on feedback it sounds like the faulty ground was the issue, rather than a short in the camper wiring. I was showing 49 volts on the door frame which is less than the 60 Mike mentioned as typical without a safety ground. Thoughts? For reference I have an 05 FWC Hawk (base model options) plus an Isotherm CR-65 fridge (DC only - direct to battery), furnace, and TriMetric TM-2030 RV.

The 60-volt measurement is an approximation of the bias voltage from ANY ungrounded appliance or RV plugged in without a safety ground. So it could be biased at 40 volts or 80 volts AC or anything in between with a high-impedance ground fault. But if the fault turns into a direct short, then the voltage will rise to the full line potential of 120-volts (in the USA).

If you want to see something really crazy, use a high-impedance voltmeter to read the voltage on the body of an iPhone while plugged into a wall charger. It will show 50 to 80 volts, but at very low current. However, there have been a few electrocution deaths in the last year from people standing in a shower and picking up their iPhones while still plugged into a wall charger. In the two instances I know of, these were aftermarket knock-offs and not Apple brand. But you never know when a low-current ground fault that gives you a tingle will turn into a high-current ground fault that kills you. And while a GFCI is supposed to protect you from these fault currents over 6mA, there's a surprizing percentage of GFCI failures that won't reset or trip properly, up to 40 percent in some cases of them mounted outside in non-weatherproof enclosures. The instructions tell you to test all GFCIs every month, but when's the last time you tested your GFCIs for proper operation?

Mike Sokol
www.NoShockZone.org