The NEC: Protecting People from Electrical Hazards in and Around Water

We’ve all heard the saying that water and electricity don’t mix. This is true for a number of reasons: water can act as a conductor under the right conditions; water can reduce the resistance of a person’s skin when they’re submersed, and electricity can cause temporary paralysis that can lead to a person drowning.

These reasons are enough to justify taking certain precautions around water when it comes to the use of electricity. The purpose of NFPA 70®, National Electrical Code®(NEC®) (www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70E)is to protect people and property from the hazards that arise from the use of electricity. The NEC has an obligation to its mission to contain requirements for protecting people from electrical hazards in and around the water and it does this in a number of ways.

Before we dive headfirst into what the NEC requires, let’s first talk about the different ways electricity can injure or kill when water is a part of the equation. First, one of the biggest areas of concern as of late has been dealing with the phenomenon of electric shock drowning or ESD. What makes ESD so frustrating is how it is nearly impossible to know that the conditions exist and that it is often impossible to detect ESD as the cause of death because the victim usually shows no sign of electric shock, but presents all of the signs of accidental drowning. This is because ESD can happen when small voltage gradients exist in the water that cause low levels of current to disrupt the body’s ability to send signals from the brain to the muscles. In other words, it is like an electrically induced paralysis and when the victim can’t swim effectively, he/she often drowns. What also compounds this problem is that the source of the stray voltage is often a boat, a dock, or a metal ladder in the pool. When a victim senses a tingling sensation, they often feel the need to swim towards safety which is often the boat, dock, or ladder. The voltage field gets stronger the closer an individual gets to the source. So, a victim might think that they are swimming to safety but in reality, they are heading right into the danger zone!

Beyond ESD, water can serve as a conductor and present that alternative conductive path that can lead to a shock or electrocution hazard. Remember, the electrons in the wire will take any and all paths back to the source, not just the path of least resistance. However, more current will flow on paths that have a lower opposition to current. Water can take a normally high amount of electrical resistance and reduce it to a level that allows a dangerous amount of current to flow. Take for instance the skin on a human body. Our skin actually has a decent amount of resistance and can protect us from lower voltage levels, which is why NFPA 70E has a voltage threshold of 50 volts where it is not considered a shock hazard. However, submerging the body in water and now the resistance value of the skin has been reduced and might allow sufficient current to flow that could be hazardous.

So, how exactly does the NEC approach protecting people in, around, and on top of water? There are a few basic principles that the NEC uses to do this. We can either provide protection from electrical hazards by removing the person or removing the hazard. There are many requirements that are aimed at providing both types of protection. Let’s explore each a little bit more in-depth.

First, let’s look at the ways the NEC takes steps to remove the hazard as that is the more popular way to achieve safety through the design of the installation. Let’s start with the tried and true workhorse of protecting personnel from shock hazard – the ground-fault circuit interrupter or GFCI. GFCIs work on the premise that what goes out must come back in. If what is coming back in doesn’t match what went out, we can shout, “Houston, we have a problem!” Now, that difference could be a person being shocked or it could simply be a ground-fault to any other conductive object that is capable of returning current to the source of the power. Shutting the circuit off under ground-fault conditions is essential to both people and property safety, but regardless of what the reason is, the fact that it could be a person makes this method all the more important. You will find requirements for GFCI protection for personnel basically anywhere where there is an established history of clear and present shock hazards, which often involve water, in both large quantities, like a pool, or in moderate quantities, like a damp location. Receptacle outlets, lighting outlets, and hardwired electrical equipment all have requirements for some form of ground-fault protection when we start installing these near a body of water or if they are associated with the handling of that water, like a pool pump motor for instance. The 2020 NEC revisions cycle saw a significant number of changes involving ground-fault protection near bodies of water. From pools to marinas, if a person can come in contact with electricity while in the water, there are going to be provisions for protecting them. It’s worth noting, of course, that when it comes to marinas, not all ground-fault protection is GFCI. Shore power to the boats is required to trip at no more than 30 mA as opposed to the 4-6 mA of a class A GFCI device that we all know as personnel protection. This is because marina protection is after limiting the electric field in the surrounding water, not the direct protection of an individual who has current passing through his/her body.

Another way we can remove the hazard is to lower the voltage to a safe level. This can be done by using certain low-voltage equipment or by bonding non-current carrying conductive parts together to prevent them from being at different potentials. Afterall, voltage in its simplest form is the difference in electrical charges between two objects. Connect those two objects with a conductive path and current will flow. If a person is in that path, current will flow through them and can be potentially fatal. However, if we connect these objects with an intentionally low impedance path, like a bonding jumper, we end up equalizing the potential difference between the two surfaces and eliminate the shock hazard. For these requirements, you will find them any time we have a scenario where people will be submerged in water. For instance, in swimming pool installations we are required to bond any fixed conductive surfaces that are within five feet of the outside edge of the pool. Also, for certain pools with a conductive shell, even the shell needs to be connected with all these other conductive surfaces to form what is know as an “equipotential bonding system.” This equipotential bonding covers the inside of the pool, perimeter surfaces around the pool, any conductive objects around the pool, and any electrical equipment associated with the pool. That way everything stays at the same electrical potential and we eliminate any potential shock hazards.

Finally, the NEC has taken other steps to protect people by either keeping the person away from electricity or by locating the electricity far enough away from the person that it becomes less of a danger to the individual. This is very common when it comes to interaction between electricity, water, and people. One example of this, still focusing on pool installations, is the requirement to keep receptacle outlets at least six feet away. That distance might not be a coincidence when we consider that the standard length of a cord on equipment like a radio or television is in that six-foot range. Beyond that, we need to get to a distance of 20 feet without having GFCI protection. This way the shock hazard has been moved a significant distance away from the person in the water, and when it needs to be closer, we utilize other methods like GFCI and equipotential bonding.

The other way we keep electricity away from individuals, is height. Overhead powerlines, lighting fixtures, and ceiling fans all have minimum distances above the water that they must maintain and in the case of overhead lines, they must maintain this separation by height over the surrounding perimeter as well. Then, when it comes to areas like marinas where there simply isn’t the ability to have the same level of protection for people in the water as it is for a pool that we build, the NEC tries to prevent the individual from going into the water to begin with. Article 555 requires signage to be installed at marinas, boatyards, and docking facilities that warns individuals not to go in the water due to potential electrical hazards that can result in death. Because the certainty of the protection afforded by GFCI and equipotential bonding are lessened in these areas, and the threat of electric shock drowning is different than electrocution, this signage is a last step in keeping people out of the water and away from the electrical hazards presented there.

While our love for recreation involving bodies of water like lakes, pools, hot tubs, and oceans is not likely going away, our love affair with gadgets, gizmos, and whatsits continues to grow. This means that these two worlds will continue to collide for years to come. And right in the middle of this competition you will continue to find the NEC fighting to protect you and your family and friends from the dangers that come when we mix these two essential parts of our lives. However, don’t forget that you, too, can join the fight and get involved in the NEC revision process. While the public input stage recently came to an end in September, keep an eye out for the first draft report (www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70&tab=nextedition) so you can track the progress and see what is next in the world of protecting people and property from the hazards that our electrified world presents. Remember, we need your help. It’s a big world, let’s protect it together!

Derek Vigstol is Senior Electrical Content Specialist with the National Fire Protection Association in Quincy, Mass.

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