Leakage current clamp meters are similar to clamp meters used for measuring load currents however, leakage current clamp meters perform much better when measuring current below 5 mA. Use a leakage current clamp meter to make these measurements. Diagnosing GFCI trips Start by measuring the leakage current and then identify the source. Adding more equipment to a GFCI-protected circuit could cause a GFCI to trip randomly, making the problem difficult to diagnose. When many pieces of equipment are operating on a circuit, the leakage current is cumulative and could be in the order of milliamps. When troubleshooting these intermittent "ghost" trips, sometimes looking for the leakage current culprit can be costly. On GFCI-protected circuits, leakage current can cause unnecessary and intermittent tripping. The insulation protecting longer conductors has higher capacitance, which can cause even more leakage current. If insulation is old or damaged its resistance is lower and leakage current could become substantial. Insulation conducts current through both electrically resistive and capacitive paths. While not perfect, even air can be an insulator. Although wiring insulation is designed to keep electricity in the conductor, all insulators have some conductivity. If a human becomes the unintended path, current as low as 75 mA can trigger ventricular fibrillation (i.e., when the heart stops pumping, which leads to cardiac arrest).Īnother name for a ground fault is leakage current.
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The usual suspects for ground-faults include worn insulation, conductive dusts, water, or other "soft grounds." Ground faults account for more than 80% of equipment short circuits and in 90% of those cases it is caused by insulation deterioration on wires and cables. Ground faults occur when electrical current finds an unintended path to ground. Instead of just resetting the GFCI, you should also investigate the cause of the trip. When a GFCI outlet keeps tripping, there must be a reason. Simple GFCI testers are available for less than $15, or for less than $150, you can purchase a high-quality, industrial electrical tester can check for energized circuits, test AC and DC voltages, resistance, continuity, and phase rotation between any two phases and GFCIs. GFCIs should be checked monthly by operating the push-buttons on the front labeled "Test" and "Reset." In addition to checking for proper operation, monthly testing also makes sure the mechanical components of the receptacle are in working order. When the comparator changes states, it triggers a silicon-controlled rectifier, which disconnects the power from the output of the GFCI. If there is a current differential, it becomes the input to a comparator within the GFCI, which changes states when the differential is around 6 mA.
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Ideally, this difference should be zero because both currents cancel. The actuating energy for standard breakers and fuses far exceeds the lethal amount, but most GFCIs trip at around 6 mA.Ī GFCI uses a current transformer to detect the difference between the line current supplied to the load and the neutral current returning from the load. Although fuses and circuit breakers are also protective devices, they are designed to protect equipment and facilities from short circuits and large magnitude electrical faults that could cause electrical fires and property damage. When a GFCI breaker trips, it It quickly disconnects the current flowing through an unintended ground path even if the amount of current is too small to trip a typical circuit breaker. GFCIs are designed to prevent bodily harm from electrical faults that could cause electricity to flow through you to ground. However, NFPA 79, the Electrical Standard for Industrial Machinery, also dictates their use in industrial applications. Most states have required GFCI outlets in certain areas of residential installations for decades. The most common types are single-phase electrical outlets used in households near water sources, such as in kitchens, bathrooms, and outdoor receptacles.
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A ground fault circuit interrupter (GFCI) is one of the most common residential, commercial, and industrial safety devices.