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Multi-Wire Branch Circuits: Saving Money, But at What Cost?

Multi-wire branch circuits can help to increase available energy and reduce costs, and proper installation can increase safe usage, but the hazards they entail may make them cost-prohibitive in the long run.

There’s a reason multi-wire branch circuits exist. These electrical conduits, consisting of two or more ungrounded, or hot, conductors connected to a single-grounded, or neutral, conductor help to facilitate greater load at less expense. Say, for example, you wanted to plug in multiple devices that suck up a lot of energy.

With a multi-wire system, you could get double the power (or more) to electrical outlets, allowing you to power myriad electronics and appliances without the fear of blowing the breaker when you operate more than one at a time. Normally, you’d have to set up multiple independent circuits to make this happen, including multiple ground wires, and that would entail a greater expense than simply splitting a system with a single ground wire.

Unfortunately, there is high danger when using multi-wire branch circuits. If the system isn’t set up correctly and the load isn’t split evenly between the two circuits, one of the hot wires or the shared neutral wire could end up carrying much more of the load than intended, and this can be extremely dangerous. So, what are the dangers surrounding multi-wire branch circuits? Can this system be safely implemented?

Why are Multi-Wire Branch Circuits Dangerous?

The presence of unintentional voltage could result in increased risk of shock (especially for electricians working on the system), but there are also dangers for users. In multi-wire branch circuits, the ungrounded conductors are out of phase and the ground wire facilitates sharing the load so that the voltage is equalized. Any mistake in setting up the system could lead to one portion having more voltage and the other having less.

When this occurs, certain electronics could experience lower voltage while others get a much higher dose. At the very least, this could lead to electronics that don’t function properly, but the more dangerous aspect is the potential for electronics to overload and overheat as they receive added voltage and wattage that they are unequipped to handle, leading to ultimate (and irreversible) failure of the device. Even instances of minor overload can add up and reduce the life of the electronic device.

The greatest danger, of course, is the damage users won’t notice occurring—the damage to the neutral conductor. Overloading can wear material components, including insulative materials, possibly resulting in arc-fault fires that originate in unseen areas throughout the home. This type of house fire could be devastating.

Is There a Way to Safely Use Multi-Wire Branch Circuits?

The National Electric Code (NEC) has provisions pertaining to the safe and proper usage of multi-wire branch circuits, notably section 210.4(B), which states: “Each multi-wire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.” The best means of complying with this safety regulation is the use of a handle tie applied to two single-pole breakers.

There are dangers inherent to using multi-wire branch circuits, even when properly installed with required fail-safes. The NEC, however, does have guidelines in place to make them as safe as possible. The best way to avoid the hazards of using multi-wire branch circuits, of course, is to simply spend the money to install multiple grounded conductors to handle energy demands.

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The Dangers of Electric Shock: What Everyone Should Know

The Dangers of Electric Shock: What Everyone Should Know

We’ve all yanked a cord out of the wall and gotten our fingers a little too close to the prongs, resulting in a mild shock. Of course, it doesn’t feel very mild. It feels like you just got zapped. Fortunately, most of these incidents do little more than remind us of the potential dangers of electrocution and cause us to act with more caution in the future.

There are cases, however, in which shocks do a lot more harm. According to the National Safety Council, an estimated 300 people in the U.S die each year from electric shocks received from either 120V or 277V circuits—in other words, your average home or commercial outlet. This might not sound like a lot of voltage, but as little as 50V administered for as little as just one second can disrupt the rhythm of your heart, and when voltage forces electrons through the human body, serious damage (and even death) can occur.

Within minutes, a serious electric shock could prove fatal if your heartbeat is disrupted, so it’s important to understand the different levels of shock and how to protect against them. Here’s what you should know.

Levels of Electric Shock

It is possible to receive an electric shock at a variety of levels; however, shockc have been narrowed down to a finite series of sensations that may occur. The first is known as “electrical sensation” and it occurs at approximately 0.25-0.5 millionths of an ampere (or mA) for women and about 0.5-1mA for men. A mild shock of this nature is accompanied by a tingling sensation.

The next level of shock is known as “uncomfortable sensation” as the feeling increases from tingling to a level of moderate discomfort. This form of shock occurs at about 1-2mA. This is followed by the “let-go threshold,” at which electrical shock will cause you to lose muscle control as muscles contract (at least until electrical current is removed). This occurs at about 9mA for women and 15mA for men.

Finally, there is “fibrillation level,” at which arterial fibrillation (or AFib) takes place. According to the American Heart Association, this is state in which the heart is quivering, rather than beating, and it can result in stroke, blood clots, or other complications. Fibrillation can occur at 75mA in just 0.5 seconds, or a mere 0.2 seconds at 500mA.

Impediments to Electric Shock

There are plenty of ways to protect against electric shock in the home or business setting. One of the best options is to install ground fault circuit interrupter (GFCI) outlets designed to protect you against direct contact with an energized conductor.

You may have noticed these outlets in your home near water sources in the kitchen and bathrooms. They are designed to trip when they come into contact with water so as to prevent electric shock, and they can easily be reset when danger is no longer present.