By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.
Did you see this story about a swimming pool drowning in New Jersey a few days ago? First they said it could be electric shock, but then they say that’s been ruled out. How else could you explain two healthy adults and an 8-year-old drowning in an above-ground pool? —Dory
Thank you for sending the link to the story HERE.
Yes, something seems suspicious about recanting the electric shock part of the story. It does seem unlikely that all three family members could drown in an above-ground pool, even though none of them could swim. Maybe the electrician checked out every possible source of electric shock and ruled them all out. However, many residential electricians aren’t trained in proper equipotential grounding and may not be aware of the latest requirements for GFCI protection of hot tubs and swimming pools. I’ll research more about this particular incident later.
In any event this is a good reason to reread my article on Electric Shock Drowning (ESD) as it pertains to your boating and swimming activities this summer. Read my previous article about ESD HERE.
But first, let’s cover a few quick definitions…
Electrocution is defined as death due to electric shock, which occurs in low-voltage circuits around 120 volts (under 600 volts is considered “low voltage”), which cause enough current to flow through your heart to send it into fibrillation. No physical damage needs to occur from the shock itself since only 10 to 30 mA (milliamperes or 0.030 amps) of current needs to flow through your body to interrupt your heart’s beating cycle.
Without CPR and an AED (Automated External Defibrillator) used in a few minutes you’ll be dead. Of course, there can also be high-voltage shock if you get tangled in the 14,000-volt (or higher) power lines from the power company substation to your local transformer, and that will indeed cause all kinds of physical damage.
Electric Shock Drowning (ESD) is something else entirely. And ESD can occur when you’re wading or swimming in freshwater near a dock or boat that has an electrical fault current flowing through it. But instead of the water acting like a low resistance copper wire, freshwater sort of spreads out the current in what you can imagine as concentric circles with different voltages. We call that a voltage gradient since the voltage gradually changes with the distance from the fault current source.
So if you were to reach your arms out to the sides in water with a voltage gradient near a boat with a grounding failure, you can have enough current flowing through your body that your muscles will lock up, and you simply can’t swim. This can cause you to slip below the surface of the water and simply drown, even though it’s technically not an electrocution. And the counterintuitive thing is that technically (and according to the autopsy) you were NOT electrocuted, you drowned from some unexplained reason.
So, never swim around a boat dock that has electricity connected to it for a boat lift or light. Never swim around a boat that’s plugged into shore power. And if you do feel your arms and legs getting so tired you can’t move them as you swim closer to a dock, then turn around and swim back the way to you came from until you regain control of your extremities, then find another place to get to land. And NEVER jump in the water to try to save someone who’s getting shocked without turning off the AC power first. You don’t want to become yet another victim.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ 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.
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