Don’t Get Zapped!

lightning-lead

Photo Credit: Dennis Brewer

by Dennis C. Brewer
October 23, 2014
Filed under Resources, Tech Tips

 

Tips on How to Make Your Motorhome Safer During Lightning Strikes

 

According to the National Weather Service, there are more than 22 million cloud-to-ground lightning strikes on average each year in the U.S. Even though the chance of being struck by lightning is low — only 1 in 600,000 — it does happen. I interviewed a lightning-strike survivor who suffered two secondary lightning strikes on one rainy day while in a campground. The first strike hit while he was sitting under an awning in an aluminum chair. The second strike, 15 minutes later, sent him to the hospital and occurred while checking on the breaker that fed power to the coach that had tripped off after the first strike. In spite of his exposure, he was one of the fortunate few who survived a lightning strike without any long-term health effects.

Understanding the Dangers

 

This multipowered portable NOAA radio is a great help to receive thunderstorm warnings.

This multipowered portable NOAA radio is a great help to receive thunderstorm warnings.

Lightning does not always come straight down from a cloud at a 90-degree angle; it follows the most conductive path along ionized air from charged clouds and can strike at a 45-degree angle from above. An approaching thundercloud or retreating cloud is just as dangerous as those directly overhead. Danger occurs when people or equipment become all or part of the conductive path as this energy charge reaches for the earth to dissipate its energy. Because there is a natural resistance in the earth, and in any objects on the ground, this zone of dissipation can cover a large area, putting everything in that area at risk of high-voltage current flows over multiple pathways.

Risk Awareness and Assessment


Become informed of the weather risks before you travel or engage in outdoor activities, and carry a National Oceanic and Atmospheric Administration (NOAA) portable weather radio.

Test the radio for signal quality at your destination location. Smartphones with data plans may have the WeatherBug or Weather Channel apps that show forecast warnings that lightning storms are imminent. Become familiar with the apps and/or listen to the weather radio or local AM/FM radio and TV stations. NOAA stations do not have complete coverage, nor do cellphone towers, so sometimes the only forecasts available are from nearby radio or TV stations. If you have an Internet connection, you can use websites such as www.weather.com or
www.wunderground.com.

Minimize the Risk

 

Smartphones with weather apps can keep you informed of weather events when a tower is nearby. Apps can also show radar and/or satellite views of approaching or receding weather fronts.

Smartphones with weather apps can keep you informed of weather events when a tower is nearby. Apps can also show radar and/or satellite views of approaching or receding weather fronts.

Minimize your risk from lightning storms and take immediate evasive action when strikes occur: Get off the water, seek shelter or occupy low ground if caught in the open. The safety rule to remember is that if you see a lightning flash and hear the sound from it in less than 30 seconds, you are in danger of having a strike at your location. Electrical storms travel fast; seek shelter right away. Do not consider trees shelter; trees are often struck by lightning, and when hit, often explode from the intense heat.

In June, “NBC Nightly News” ran a clip of a moving pickup that took a direct hit of lightning as it motored along the highway. The lightning ruined electronics in the truck and the occupants reportedly couldn’t get out without help, but it proves the next point. When a lightning storm is present, you are safer inside; inside nearly anything, except a tent or tent-like structure. The Faraday effect helps to keep you safe inside your home, motorhome or car. If caught out in the open, find and go to the lowest ground or ditch, while avoiding water, and stay put for at least 30 minutes after the last thunder boom.

Campground and RV Lightning Safety Factors


Staying safe from lightning strikes at campgrounds is a responsibility shared by the motorhome owner and park operator. Motorhome owners should test power cables for continuity and check and maintain electrical connections or have their service provider or dealer perform an electrical safety check annually.

To maximize safety there are three wiring details that should be, but are rarely completely understood. All three are of equal importance and must be fully functional to work together as a system to reduce the risk of injury and equipment damage from lightning that strikes anywhere in or even nearby the park. Let’s take a closer look at these details to understand how this risk can be mitigated by testing and complying with standards.

Grounded Conductor

 

This supplemental ground wire and rod were installed only to improve the park’s lightning safety.

This supplemental ground wire and rod were installed only to improve the park’s lightning safety.

On U.S. electrical systems, one current-carrying conductor is connected to the earth. In your RV’s wiring system, the neutral wire when correctly installed at a common three-prong 120-volt AC outlet will be the wider contact. The neutral (white) conductor is a part of the normal circuit-return path for operation currents powering all 120-volt AC lights and equipment on board. Lightning striking any one of the nongrounded current-carrying conductors will travel through lights, equipment, appliances and electronics to reach earth through the neutral conductor path unless you have sufficient surge protection on these lines. Every motorhome connected to a pedestal on the same transformer circuit shares the surge risk if any lines are hit.

Bonding Wire


Household living areas including motorhomes are required to have a bonding wire commonly referred to as the “ground” in 120/240-volt AC electrical circuits; it can be color coded green or be bare copper. Although this wire is also grounded in the electrical service panel or at the pedestal to the same lug buss assemblies as the neutral, its main purpose is not to carry normal operating currents. Its main purpose is to provide an alternative return path for any electrical voltage escaping from its intended return path, the neutral wire. This bonding (aka ground) wire then serves two primary functions. First, shunting the user of electrical equipment from becoming part of a return path in the electrical circuit; its other job is tripping the circuit breaker to off when a to-equipment-case (short) fault occurs. When using a surge protector on a power cord, the neutral wire (and in some surge models the bonding wires) provides the return path for surges higher than a specified voltage. Typically any voltage higher than 300 to 600 volts are shunted by the surge protector. These surges (overvoltages) can occur from primary or secondary line faults, problems at a substation or generation station, and from lightning strikes anywhere on the electrical supply line.

Grounding


The sole purpose for grounding is to carry voltages from lightning strikes harmlessly to the earth. At the motorhome, the primary electrical path to ground from a lightning strike will be found through the bonding wire and the grounded conductor (neutral) wire because they are both connected to the same lug. Non-intended secondary paths may also be present from metal pipes or cables used to hold down awnings or any other metal objects or wire touching the motorhome and the pavement or earth under and around it.

Two risks are evident when you hook up a power cord to an electrical pedestal. The first is the quality of the connections for the bonding and neutral wires on the electrical cord and plugs that connect to the outlet on the pedestal. This is true whether you connect with 120-volt AC; 15, 20 or 30 amp; or 120/240-volt AC 50-amp connections. The second risk is that the pedestal may not provide a sufficient path to ground for all the electrical energy present in a lightning strike. Any excessive resistance to ground on the neutral conductor and the bonding wire at the pedestal can lead to severe risk of electrical shock for anyone coming into, going out of or standing near the motorhome when a direct or secondary strike path occurs. Regrettably, many RV parks have been wired in such a way that the only good grounding is at the service panel at a building, on a pole-mounted service distribution panel or at a dedicated ground-mounted distribution panel, often a great distance from the RV. Sure, the neutral conductor and the bonding wire may well be in place and conducting to that point, sometimes 600 feet or more away from the RV hookup pedestal, but that is not always good enough when protecting the occupants from lightning strikes. The aboveground voltages in this scenario could be in the range of thousands of volts, and every RV hooked to that circuit is at risk of incurring excessively high aboveground voltages from a strike and risk becoming part of the lightning current’s shared path to earth.

To further understand this, consider the common sight of the bird on the powerline wire. A crow lands on a 70,000-volt power-distribution wire, crows a few times, flies away and nothing happens to it. The bird and the wire it landed on could be 70,000 volts or more above­ground potential but there was no ground path anywhere nearby. If everything is connected and there are no alternative paths to ground, there is no risk of shock or injury. RV park owners can protect their visitors by making sure that all the ground wires and neutrals back to the service panel are intact, connected tightly and properly grounded to National Electrical Code standards.

With supplemental ground rods at every pedestal and with the ties back to the distribution panels intact and grounded to meet code when lightning strikes in an RV park, it brings the entire park up to whatever voltage the lightning strike is for an instant. All the RVs in the park become like the birds on a wire with no alternative paths to earth for the current from a lightning strike to follow. A larger area of dissipation provided by multiple interconnected ground rods with low resistance to earth reduces the potential risk of damage or injury.

Safety-Checking Items on Your RV

 

A small volt/ohm/amp meter can be used for testing the resistance of the ground and neutral wires.

A small volt/ohm/amp meter can be used for testing the resistance of the ground and neutral wires.

Here are some ways to minimize your personal risk. First, with the inverters and generators turned off and also while not plugged in to any power source, periodically inspect the quality of your power cord. The plug tongs should be straight and clean, and the cable/cord should be undamaged with no wires showing or any of the cable sheathing frayed or cut away. Check the connections on the bottom of the power-distribution (breaker) box for tightness of the wires on the connection lugs; they should all be snug, tightly holding the wires. Repair or replace any damaged cords, plugs or sockets.

Next, test the resistance of the power cord. Bring the cable-end plug in to where the main power-distribution circuit breaker box is located. Use a volt/ohm/amp meter to measure the resistance at the ground prong to the bonding connection lugs in the breaker box. Do the same for the neutral wire.

Testing the line resistance from the plug end to the bus lugs in the breaker box should be done at least once each year. Calculate or tape measure the total wire distance from plug to the breaker box to determine the ideal resistance for the wire size. Theoretically, if the reading is much more than .033 to .004 ohms (.0011 ohms per foot) for a 30-amp 25-foot-long power cable, or higher than .01 to .02 ohms (.0004 ohms per foot) for 50-amp 25-foot-long cables, then some replacements or repairs are indicated. In reality, most inexpensive meters will show about 1 to 2 ohms for the full length of a 25-foot cable plus the connections leading to the breaker box. Test both the neutral (grounded conductor) and the bonding conductor. The two readings should be very nearly the same unless the cord has a smaller-gauge wire for the bonding connection. If the readings are more than 10 ohms, you have an issue that needs immediate attention. In more modern coaches, the bonding lug and the neutral lug in the breaker box are not connected except when plugged in at the pedestal. That is why the next step, to test the park’s pedestal outlets before connection, is so important.

This tester, made by Commercial Electric ($11), is intended for use in outlets. An adapter can be used to extend the tester for use in 30-amp/120-volt AC outlets.

This tester, made by Commercial Electric ($11), is intended for use in outlets. An adapter can be used to extend the tester for use in 30-amp/120-volt AC outlets.

The third task to reduce risk is testing the park’s pedestal. Test for the following at the park’s pedestal for the 15-, 20- or 30-amp outlets before you connect for these indications: open ground, open neutral, bad ground and reversed polarity — all indications of an incorrectly wired or faulty pedestal. Beyond the potential for damage to your equipment, any of these faults increases the risk of injury from a nearby lightning strike.

If the 15/20-amp circuits and 30-amp outlets are not correct, odds are the 50-amp may not be either. Do not hook up to any pedestal that fails these tests.

Some 50-amp portable surge protectors, such as the Surge Guard Model 3470, can also test for faults and “elevated ground voltage” indicating that the grounding system (aka lightning protection) is not up to par before you hook up.

Including these preventive steps in your routine takes very little time and reduces risk of injury or death from this natural yet very powerful phenomenon.

 

 Lightning True or False?

 

  • Lightning does not strike twice in the same place. (False) The same area can be hit multiple times in a lingering storm.
  • It’s safe to help a victim of lightning. (True) It’s OK to administer CPR and render aid; the victim does not stay “electrically charged.”
  • Rubber shoes will keep you safe from lighting. (False) Lightning voltage is too high for shoes or rain suits to make a meaningful difference.
  • Being inside a car is not safe. (False) The metal shell provides some protection.
  • Golf clubs or umbrellas will not attract lighting. (False) Any metal object and added height increases the risk.   

 


 

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