By Mike Sokol
If you recall the survey we did July, 2010 in RVtravel.com, you know that 21 percent of RVers who responded had been shocked by their RV. Review the 21 percent report at www.noshockzone.org/15. What follows is the fifth segment of a 12-part series about basic electricity for RV users and how to protect yourself and your family from shocks and possible electrocution.
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.
What’s an Ampere?
We often abbreviate ampere as “amps,” but basically it’s a measure of how many electrons are flowing through a wire or conductor per second. The actual electron count isn’t important, so you can think of it as gallons of electrons per minute, using our water tank model [illustrated in earlier articles in this series]. And, yes, we call this effect “current” both when talking about the flow of water in a river as well as the flow of electrons in a wire. Pretty cool, eh?
Pumps and Hoses
If you look at the first illustration, you’ll see a pump pushing water around in a circle. And depending on the pressure produced by the pump and the size of the pipes, you’ll either pump a lot of Gallons Per Minute (GPM) or a little. In this case we’re using a pump that can produce 120 PSI (Pounds per Square Inch) pressure to move water around a pathway or circuit. And because we have a large diameter pipe all around, this circuit can support a lot of current flow without losing hardly any energy or pressure in the process.
As you can see from the next illustration, if you use a very narrow pipe for part of this flow, your gallons per minute (GPM) flow will be very low. So a pump that might be able to push 10 Gallons Per Minute through a big pipe could be restricted to perhaps 1 GPM if you use too narrow of a pipe for any part of the circuit. And just like the garden hose you use to water the plants, it can’t deliver enough flow if it’s too small in diameter or too long in length. The exact same thing happens to electricity as it flows through a wire like an extension cord.
Take a look at the illustration of the electrical circuit on the left. Instead of a pump let’s substitute a battery or generator, and instead of a pipe use a wire going around in a circle, which we’ll call a circuit. If the wire is large enough in diameter, then the generator or battery can push the full 10 amperes through the circuit, which is the amount of current your coffee pot might require to heat up. And as long as you don’t try to push more amperes of current through a wire than its rated for, then all should be fine.
However, the exact same generator or battery could be in trouble attempting to push those 10 amperes of current through a skinny wire or extension cord. And while you may notice a significant drop in flow from your garden hose if it’s a bit too skinny, you may not notice the problem you’ll have from a small extension cord when it’s supporting a lot of current flow. Instead of just restricting the water flow in a hose, electrical wires can heat up to the point of catching on fire if you try to push more current through them than they’re rated for. How much current is OK? Well, glad you asked.
Size Me Up
For those of you unfamiliar with extension cord specifications, the lower the number of the gauge, the thicker the wire and the more current that can flow through it without overheating. For example, a 14-gauge extension cord might be rated for only 15 amperes of current flow, while a 10-gauge extension cord could be rated for 30 amperes of current, depending on total length of the cable and type of insulation.
More on this in a future article, but here’s the basic AC amperage capacities of AWG [American Wire Gauge; standardized U.S. wire gauge system] standard wire sizes. As you can see from the chart, the lower the gauge, the larger the diameter of the wire and the more current it can carry without overheating.
Also, it’s often noted that you should make the wire one size larger than called for in the chart if you’ll be running a long distance. NOTE: 50 or 100 ft of extension cord from the campsite pedestal to your RV is a very long distance. Do not expect a 12-gauge extension cord to carry a full 20 amps of current over 50 feet or more. In that case, go to a 10-gauge cable to handle the current over that distance. And you can see that if you want to draw the 50 amps from a 240-volt receptacle, you’ll need a 6-gauge extension cord if you’ll be drawing current from the outlet at maximum capacity. This will also minimize your voltage drop.
Did I say “voltage drop”? I’m sure you’ve heard of it, but how many of you know what it really means? Well, that sounds like a good subject for the next article. So stick around while we continue learning about RV electricity and how to stay safe while using it.
•Extension cords can heat up and catch on fire if you exceed their amperage rating by drawing too much current.
•The lower the gauge number (AWG) on an extension cord or wire, the more current it can safely carry without overheating.
•Electricity needs a complete circuit for current to flow from the high voltage side to the low voltage side of the generator or battery. That current is measured in amperes.
Part VI of this series will cover how amperage draw causes voltage drop, which is why your coffee pot can cause your lights to dim in your RV. Stay tuned.
After you’ve read this article at RVtravel.com, take a trip over to www.NoShockZone.org and send us your comments and suggestions. We love to know how we’re doing with this important project.
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 firstname.lastname@example.org.
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