RV Electrical Safety: Part I – Volts

Jul 29th, 2010 | By | Category: RV Safety
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The No~Shock~Zone:
Understanding and Preventing RV Electrical Damage— Part 1
Copyright Mike Sokol 2010 – All Rights Reserved

If you’ve read the survey we did last July at www.RVtravel.com, you know that 21% of RVers who answered the survey  have been shocked by their RV.  What follows is the first in a 12-part series about basic electricity for RV users and how to protect yourself and your family from shocks and possible electrocution. Review the 21% report at http://new.noshockzone.org/15/

This series of articles is provided as a helpful educational assist in your RV travels, and is not intended to have you circumvent an electrician. The author and the HOW-TO Sound Workshops will not be held liable or responsible for any injury resulting from reader error or misuse of the information contained in these articles. If you feel you have a dangerous electrical condition in your RV or at a campground, make sure to contact a qualified, licensed electrician. 

RV-Safety

While RV’s as wired from the factory are inherently safe, they can become silent-but-deadly killers if plugged into an improperly wired extension cord or campsite outlet. This is because RV’s are basically a big cage of metal insulated from the ground by rubber tires. It’s up to you, the RVer, to make sure the frame and body of your RV is never electrified due to poor maintenance, bad connections, or reversed polarity in a power plug. This so called Hot-Skin problem is what causes a tingle when you touch the doorknob or metal steps of your RV while standing on the ground.

Just the Basics

I can remember teaching myself basic electricity when I was 12 years old. It seemed like such a mysterious force that could do most anything from run a fan to shock you if you touched a wire. I wanted to know all about it. So for two years I read every book I could find in the library, every Popular Science magazine I could get my hands on and ran “electrical experiments” in my bedroom. By the time I was 14 years old I knew the basics of DC electricity and how it worked. That interest is what launched my career in audio engineering.

Now most RVers really don’t want to learn about electrical engineering. However, everyone should be able to learn how to test for and avoid electric shocks or electrocution at a campsite. With that in mind, there are some novel ways to think about and teach basic electricity to the casual RVer. I promise little or no math, no fancy schematic reading and certainly no memorization of formulas. It’s my privilege to teach you basic electrical safety as long as you do one thing for me — let us know if the information is making sense and is helpful to you. So after reading this post on RVtravel.com, head over to www.NoShockZone.org and give us some feedback, good or bad. The failure of the student to learn is the failure of the teacher to teach, and I take my teaching job seriously. So feedback is encouraged.

Why Do We Get Shocked? (What is This Volts Thing?)

What’s so hard to understand about electrical shocks in general is that they don’t seem to happen for any obvious reason. For instance, you can watch a pigeon on a power line that’s not being shocked, yet sometimes touching a power tool yourself while standing on wet ground can bring you to your knees. Just why is that?

Well, the first thing to understand about electricity is the concept of Voltage. Think of Voltage as electrical pressure, just like the pressure in a tank of water. Now in a tank of water we measure pressure in something called PSI (pounds per square inch), which will of course increase if we get a deeper tank. This pressure is caused by the pull of gravity from the Earth and if you hook up a hose to the tank, the water will flow toward the ground. So while 10 PSI of water pressure from a short tank might give you a trickle of water when hooked up to a hose, 100 PSI of water pressure from a really tall tank gives you a stream that will spray much farther.

Water — and electricity — tries to flow to the side of least pressure. You can imagine that if a pipe is connected between two tanks with exactly the same water level and pressure (say, 100 PSI) there will be no flow of water through the hose. It just sits there and does nothing because the system is equalized. However, if you connect one tank with 100 PSI of water pressure to another tank with 10 PSI of water pressure, water will flow from the high tank to the low tank. We measure this water flow in gallons per minute.

 Under Pressure

The same thing happens with electricity. You’ve often heard of “completing an electrical circuit,” but think of it as different electrical pressures. Getting back to the pigeon on the power line, if both of the bird’s feet are on the same wire, they’re at exactly the same electrical pressure. Because they’re at the same pressure, there’s no electrical current flowing through the bird. If, however, the pigeon is unlucky enough to touch one foot on a power line and a wing to the grounded metal power pole, then his one foot will be at 1,000 volts (think PSI of water pressure) and his wing at 0 volts (think an empty tank). This will cause a lot of current to flow through the bird, which we’ll measure in Amperes. And indeed 1,000 Volts across a pigeon can cause a bird explosion.

Hot Skin Shocks

Now, consider your RV. Sometimes you may feel a shock when you touch your hand on the doorknob, and sometimes not. What’s happening is that there could be an electrical voltage (think pressure) on the body of the RV, which is waiting for some different electrical voltage level to head towards. If your entire body is inside the RV, then like the pigeon every part of you is at exactly the same voltage. And like the pigeon, there’s no current flow and you feel no shock. However, if one foot is on the ground at essentially zero volts and your hand is on the door of your RV that is at 100 volts, you become the pipe and the different electrical pressure (Volts) will push current (Amps) through your hand, arm, chest cavity, torso, leg and foot. If your foot is on dry ground there might be so little flow that you might not even feel it. But stand on the damp ground with a wet shoe, and you’ve made a zero voltage connection to the ground with your foot. In that case, a lot of current will flow through your body if you simultaneously touch a doorknob or metal step that’s at 100 Volts or so.

Heart to Heart

The dangerous part is when this electrical flow goes through your chest cavity since right in the middle of you is your heart, and hearts don’t like to be shocked. That’s because the beat of your heart is controlled by electricity, which comes from your own internal pacemaker. And just like a clock radio can be scrambled by a nearby lighting strike, even a small amount of electrical current passing through your heart can cause it to start skipping beats and cause a heart attack. Just how little? Glad you asked.

I’m sure by now you’ve seen the 20-Amp marking on a circuit breaker. That means it can supply 20 Amps (Amperes) of current flow when asked to do so.  Again, you can think of it as gallons per minute of flow, and Amps are indeed a count of electrons per second flowing through a wire (think pipe). Much more on that later, but it takes less than 5 milliamps of current to cause your heart to go into fibrillation mode. That’s just 5/1000 of an Amp or 0.005 Amps of alternating current to cause what’s essentially a heart attack. It takes just 30 Volts of Alternating Current (AC) to stop your heart if your hands and feet are wet. On the strange but true side of the coin, while 60 Hz Alternating Current (AC is what comes out of your wall outlet) can cause your heart to go into fibrillation and stop pumping blood, the rescue crew will use Direct Current (DC) of several hundred Volts to reboot your heart and get it beating regularly again. That’s what they’re dumping through the paddles placed on your chest — Direct Current from big capacitors like you see charging on the TV dramas before they yell “Clear!”

Play It Safe

The first rule of staying safe from electrocution is to keep your heart out of the current flow. You can see that getting shocked from hand to hand or hand to foot is about as bad as it can get. That means if you’re plugging in your RV plug to a campsite receptacle with one hand, the last thing you want to do is hold onto the metal box with your opposite hand or be kneeling on the wet ground. If you have two points of contact and something goes wrong (like you touch a bare wire), the current will flow to your opposite hand or feet, passing through your heart in the process. So always turn off the circuit breaker when plugging or unplugging your campsite power. Not doing so is to invite death by electrocution, and nobody wants that.

Quick Tips

  • Use only one hand to plug or unplug any power cables
  • Turn off breakers in the pedestal before plugging or unplugging campsite power
  • Never stand or kneel on wet ground while making electrical hookups
  • If you feel a shock from any part of your RV, do not get into your RV. Shut off the pedestal circuit breaker immediately and alert the campsite manager.

Part 2 of this series will cover how to measure voltage at the campsite pedestal before plugging in. Stay tuned and stay safe.

Mike Sokol is the chief instructor for the HOW-TO Sound Workshops (www.howtosound.com) and the HOW-TO Church Sound Workshops. He is also an electrical and professional sound expert with 40 years in the industry. Visit www.NoShockZone.org for more electrical safety tips for both RVers and musicians. Contact him at mike@noshockzone.org.

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27 Comments to “RV Electrical Safety: Part I – Volts”

  1. Gail West says:

    Read your article on RV Travel Weekly. It was well-written. Good analogies. Enough information to understand the principles involved and the “reasons why” for the tips or words of caution.

  2. Don Schulte says:

    Mike, i read your first article and found it very helpful. I myself understand the basics of electricty and am the mechanically inclined type. I understood exactly what you were trying to convey. I’m thinking though, looking back on times I have tried to explain some technical things to family or maybe a friend, that no matter what I say you can still get that look of “I dont really understand you”. I’m assuming there will be a lot of people who read your article and left with that puzzling look also. I guess what I’m trying to say is I have the interest to want to know how things work, whereas I believe the majortiy of people who will read your articles are wanting to know how to prevent a possible accident. I am not critical of your methods at all, in fact I think it a very well written article, and I’m sure you toiled at figuring the best way to present it for a varying audience. Just thought I might share my feelings of trying to explain things to people and what I felt. Great job, and thanks. Don

    • Mike Sokol says:

      Don,

      Your comments are spot on. I know that most people really don’t want to learn about electricity, but that’s mainly because electricity is both invisible and overwhelming. I think that if all RVers would read just one NSZ article a week and maybe re-read it a few times, it will all “stick” at some point. That 20 minutes or so spent reading each week will be rewarded with not only a better understanding of shock hazards and how to avoid them, but also a greater understanding of electrical appliances in general. America is falling behind the rest of the world in math and engineering, mainly because we’re afraid to understand how things work. But these articles are a small step towards understanding more about a technology that each of us holds in our hands everday… electricity. From your cell phone to your computer to the CFL bulbs in your house, we are immursed in advanced electronics everyday. And understanding electricity is just one small step towards knowing how to make it all work for you, not against you.

      (soapbox mode off) Mike

  3. Larry Andrew says:

    Thanks for focusing on RV Safety. Your first article hit home….so to speak because of a recent experience we had related to use of our Honda 2000 generator. We have a fifth wheel with a full solar system including 2 8d batteries that usually suffices when we are dry camped. We carry the portable generator as a back up for cloudy days, etc.

    We were recently camped for 10 days in Wyoming at a Forest Service campground. We found it necessary to use the portable to supplement the solar because of limited sun for a few days. Anyway, I was continually getting zapped when I touched the metal door handle getting in and out of the rig. I tried to research the issue of grounding for the generator but that issue is so complex I couldn’t determine what to do. Is grounding of the generator the problem?

    I have a fairly sophisticated electrical management system that I had to bypass when using the generator because it would shut down rig electrical power so that I had to turn it off to use the generator. I went ahead and used it quite a bit and all the systems worked fine except that I kept getting zapped. Any advice?

  4. m meredith says:

    great article

  5. m meredith says:

    Great article on rv electric. Thanks

  6. Ed Owens says:

    Great introductory article with already many good points to ponder (1 hand to plug in, turn off the switch, etc.) Keep it up. Looking forward to the series.

  7. Michael Erps says:

    Good information, looking forward to reading more. I have always turned off breakers before plugging in my rv cord. Unfortunately I see RV’ers plug in all the time with the breakers on.

  8. Thanks for writing this. A really good article!! I’m looking forward to reading the ones yet coming. Your presentation is simple enough that even an old traveler can understand.

  9. Richard Charter says:

    So far your presentation is really easy to understand. Nice way do it when a lot people don’t know anything about electricity. I use to be a tv eng. in the ser. so it was to easy for me but keep doing that way someone will be helped i’m sure.

  10. Proto says:

    Good article, well written with plenty of information, however since you titled it volts and yet still went slightly into amps I could see where some people would get confused. I was able to follow the flow (sorry) of the article but I always worry about the students that are just learniing and have no background.

    • Mike Sokol says:

      Ah yes… it’s nearly impossible to talk about volts without mentioning amps. Like you can’t talk about water pressure without discussing what happens when you cut the pipe and the water starts flowing. Now there’s no guarantee that everyone will learn every point of these articles since some people just don’t do well by reading without real hands-on training. That’s because each of us learn differently. However, my main gig has been presenting technology seminars for the last 10 years and I’ve learned a lot about teaching complex subjects to non-technical people. It’s not always a perfect system, but most of the time nearly everyone in these seminars learns the basics. So if everyone reads all 12 articles in the series, most everybody will learn the basics to keep out of electrical trouble around RVs. However, I’m sure you all will let me know how I’m doing. Your feedback is always welcome.

  11. Teri says:

    Mike,
    Very informative info on a difficult subject. I am a Campground owner and I’d love to have you visit us in the winter. We are a small 30 site RV Park but we are close to full most of the winter and I know that RVers would love to learn more about RV electrical safety.
    Thanks for the article.
    Teri

  12. Sherman says:

    Great job Mike. I really enjoyed meeting you at SprinterFest East this past Saturday and being able to talk a bit about this series on RV electrical safety (among other things). Your electrical safety demo with “Flash” (an action figure with a flash bulb head) was very cool!

    I’m not a teacher but I enjoy explaining electrical and mechanical concepts to others (whether they enjoy it is another question…). I’ve found the water analogy you used to be the easiest for most people to understand. Graphic animation (like that found on http://www.howstuffworks.com) can sometimes help.

    As others have mentioned (and as you well know) it can be very difficult to teach — particularly certain subjects. I remember when I was in college I was often frustrated by the PAs’ inability to explain things. The PAs were typically graduate students who presumably understood the basic concepts of calculus (for example) very well, but they did not all have the ability to teach. I’m sure it was frustrating for them as well as the students sometimes.

    An additional tip might be to use a rubber mat outside the entrance to the RV, where people are most likely to stand and touch it. Needless to say, it’s always best to avoid any possibility of there being a difference in potential between the RV and earth ground, the mat would just be an added precaution (and help keep the carpet clean!). I work for Metro in D.C. and it is common practice for the employees that work on or around the 750 Vdc ‘third rail’ to cover it with a rubber mat, even if it is de-energized.

    My wife and I are just getting interested in RVing so I’m not familiar with what the RV campgrounds provide, but it would be good if every RV had a dedicated ground wire and every RV site with electrical service had it’s own ground, so that even if the shell or frame of the RV became ‘hot’ the circuit breaker would trip.

    I wonder if there would be some way to wire RVs with a GFCI that would protect against this sort of problem?

    I meant to tell you, I saw a Sprinter at SprinterFest that had one of those inexpensive electrical outlet testers plugged into an outlet. The type that has three lights — 2 yellow and one red IIRC. That might be worthwhile. Not fail-safe, but as long as the owner remembers to check it it could be useful.

    Does the NEC cover RVs and/or RV campgrounds at all?

    Thanks for all of your hard work on this. I’m sure you will save some lives.

    Sherman

    • Mike Sokol says:

      Sherman,

      Yes, I’m going to recommend a basic rubber mat (like a shower mat) to stand on while checking live voltage on a campsite pedastal. I used to stand on a wooden chair with one hand in my back pocket while working on low-voltage (under 500 volts) live circuits. The 10,000 volt live stuff starts to get scary, and the 250,000 volt stuff in INSANE. And you are correct that an inline GFCI could save your life. But many RVers bypass the ones found on campsite outlets since they “trip too much” due to electrical leakage in the RV itself. Of course, it’s trying to save your life, so if you bypass the GFCI by using a 30 amp to 20 amp adapter plug and something goes wrong with the plug polarity or RV wiring, you can receive a full 120-volt shock with dire consequence. Modern RVs all have Ground Fault Interrupt outlets, but sometimes people will pull those out which is really dangerous as well. I’ll cover GFCI theory and usage about article #9 or so. And yes, I currently recommend a $5 outlet tester with the 3 lights to be plugged into your RV and left on. It’s a good warning sign when something has gone wrong somewhere else in the campgrounds that has electrified your ground somehow.

  13. Joe Jeter says:

    Thanks for the very important info. Looking for ward to the other installments. One question, should you turn the pedestal circuit breaker back on after plugging in, and if so, when?

    • Mike Sokol says:

      You’re jumping a bit ahead to Part II which will publish next week, but essentially after you’ve made the plug connection into the campsite pedastal but before anybody jumps into the RV, you’ll want to turn the CB (circuit breaker) back on. At this point you’ll want to confirm that you don’t have an open ground or hot-skin condition where your RV has been electrified. A simple 3-light outlet tester plugged into an RV receptical can confirm you don’t have a polarity reversal due to a miswired extension cord plug or campsite outlet, and a non-contact AC tester can confirm the body of your RV is safe to touch. Should take less than 30 seconds to do these simple tests. That last bit will be in Part III of the series, so stay tuned.

      Mike

  14. KEITH KOLB says:

    Thanks for your write up on electricicity, sometimes we all need a refresher course. The one thing I forgot how to do is to do a amp check on the draw of a microwave I have for my rv. I purchased two microwaves that claim to draw 700 watts, I also have a 1000 watt honda generator that wont pull the microwave so trying to figure the actual draw and requirements

    • Mike Sokol says:

      The rating of a microwave oven is it’s power OUTPUT, not its INPUT. So if you have a microwave that’s rated for 700 watts, that’s its power output. However, all electronic devices are inefficient, wasting some of the input power in various ways. So a 700 watt OUTPUT microwave might draw 1,100 watts from the INPUT AC power line. Plus anything with a motor will have a peak power draw that could be another 50% on top of that for a fraction of a second. That’s probably what’s kicking out your generator. I plan to detail how to figure this all out in a later article in this series.

      Mike

  15. Jake says:

    Can I get an electric shock (Hot Skin) from a bad step motor?

    • Mike Sokol says:

      Jake,

      Yes you certainly can. Anything that’s connected to a power supply that’s connected to a power outlet can have its chassis electrified with a “hot skin” condition. So even if your using a 12 volt DC supply to power your stepper motor, that power supply is probably bonded to the “safety ground” in the outlet. If that outlet is wired incorrectly (say, with a Reverse Polarity Bootleg Ground – what I call an RPBG) then the chassis of the stepper motor controller and the stepper motors themselves can be electrified to 120 volts. But they will operate normally as if nothing is wrong, and can do so for years. However, if you’re standing on damp concrete with wet leather boots (been there, done that) than touching the chassis of the stepper motors (and anything they’re bonded to) will result in a shock to you. How bad of a shock depends on a number of factors, but it can certainly kill you or anybody else who touches it. Get a NCVT (Non Contact Voltage Tester) from Fluke, Amprobe, Sperry, Greenlee, or Extech, and check the machine chassis for voltage. If any of the testers “beep” then it’s time to get out the DMM and investigate what’s really wrong. Any machine with electricity in it and a grounded plug should NOT show more than 1 or 2 volts referenced to earth ground.

  16. Patti says:

    I’m one who wants to know more than how to not get shocked…want to fix it myself, make changes, and, oh…just ordered a Honda eu2000. Gotta go, lots of reading to do. One thing that is working is exactly what you said–rereading and keep reading whatever I find. It starts to stick to the wall that way. Thanks bunches–Patti

    • Mike Sokol says:

      Patti,

      I taught myself all about electricity much the same way when I was just a kid. I just kept reading everything I could get hold of, and one day I woke up and understood the basics. At that point you can start adding on all sorts of cool stuff like semi-conductors and inductors. I’ve tried to tailor these basic electricity articles to be easily digestible so that if you read one every few days and repeat the sequence a few times, you’ll soon have it all in your brain. Let me know how you do with your electrical studies, and pass on these articles to every RV’er you know.

  17. Johna138 says:

    Great, thanks for sharing this article. Really Cool. dbefdddeefeg

  18. mkawa says:

    Hi good article, but am no professional at this things but today while i was checking my outlet(3 pin with live, neutral and ground), with a neon contact tester (on the live wire point/hole) and i got a shock, i don’t know the reason, its not the static build-up
    i tried it again it was the same, i thing its because of the ground wire which might got cut in between or something like that.. its not the fault of tester, tested with other neon tester same result.

    • Mike Sokol says:

      How exactly are you using the neon contact tester? Old electricians would hold onto one lead with their hand, and probe with the other lead. But that can be dangerous under certain situations. What make/model tester is it?

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