By Mike Sokol
I’ve just started reading your RV Electricity articles, and it seems there are hundreds of them. How long have you been writing this stuff? Can you repost some of the simpler ones so I can learn about electricity without hurting my brain too much? —Dawson
While I have been a technical writer and seminar instructor for more than 30 years, the vast majority of that has been about big sound systems, including how to mix bands as well as keep safe around electricity. But I’ve been writing for the RV industry for around 9 years or so, and have published a few hundred articles on electricity as it relates to campgrounds and RVs. I think this a great point to visit the way-back machine and see how I got here.
What follows is the first in the reboot of my 12-part series about basic electricity for RV users and how to protect yourself and your family from shocks and possible electrocution.
While RVs 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 RVs 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/Contact-Voltage is what causes a tingle when you touch the doorknob or metal steps of your RV while standing on the ground.
Just the basics
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 basic ways to think about and teach basic electricity to the casual RVer.
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. 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 try 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.
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 11,000 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, 11,000 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 lightning 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.
- 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, shut off the pedestal circuit breaker immediately, pull the shore power plug, and alert the campsite manager.
- Do not get into an RV that has shocked you until you have disconnected it from shore power.
Part 2 of this retro-series will cover how to measure voltage at the campsite pedestal before plugging in. Stay tuned and stay safe.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
©Mike Sokol 2010/2019 – All Rights Reserved
Hi Mike. In your quick tips, you wrote: “Use only one hand to plug or unplug any power cables.”. Can you help me understand why you recommend this?
Read just above the “Tips” again