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Q1. Is PPE required when working on 120-volt circuits?

NFPA 70E ® 130.4(F)(1) states the qualified worker’s hands must be insulated or the energized parts must be guarded before they can enter the restricted approach boundary. The restricted approach distance to 120 volts is listed in NFPA 70E ® table 130.4 (D)(a) as “avoid contact”.  Ask yourself can I avoid contact without trying? In other words, can inadvertent contact with exposed energized conductors be made? If the answer is yes rubber insulating gloves need to be worn.

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Q2. How many times can I wash my arc flash gear before it no longer protects me?

The simple answer is that the arc-rated protection will not wash out or wear out, in other words, if properly cared for, which includes proper laundering, the garment will protect as required for the lifetime of the garment. However, we always recommend that you check with the manufacturer for end of life instructions and guidance.

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Q3. Won’t the blast pressure produced above 40 cal/cm2 cause a fatality even if wearing arc flash gear?

The correlation between incident energy and blast pressure is a commonly misunderstood. In fact, blast pressure is associated with high amounts of fault current. Interestingly, high arc flash values may come from low fault current or high fault current. The concept of high fault current causing a large arc flash is intuitive. However, low fault current can cause a breaker to take longer to trip, this increases the time available for an arc flash to grow resulting in a higher incident energy rating. Simply put, there is no direct correlation between blast pressure and incident energy.

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Q4. What causes an arc flash to be big or small?

First of all, it’s important to decouple arc flash hazards from shock hazards. Just because there is high voltage, does not mean there is high arc flash potential, in fact many times it is quite the opposite. The biggest contributors to an arc flash are fault current and clearing time.

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Q5. Why do I need an Arc Flash Evaluation?

OSHA provides a “general duty clause” – Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees. It’s a short statement but carries a lot of weight.

Concerning electrical systems, there are two hazards: “Shock” and “Flash”. Both of these hazards must be identified in order for the requirements of the general duty clause to be met. With electrical shock hazards, it is straight forward to verify the voltage of an electrical component and thus protect yourself from the hazard with appropriate methods. Unfortunately, arc flash potential is not that simple. You must calculate the incident energy to satisfy the requirement for selecting appropriate PPE and determining how to work around the hazard.

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Q6. How much does an arc flash evaluation cost?

The answer isn’t always straight forward but this will help you estimate cost: Total square foot of your facility / 8 = ESTIMATED Price of an evaluation.

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Q7. Can I wear class 00 (500-volt) gloves when working on or near 480-volts?

ANSI C84.1-2016 Establishes nominal voltage ratings and operating tolerances for 60Hz electric power systems above 100V. The upper level of the range for utilization equipment with a 480-volt nominal rating would be 504 volts (range A) and could go as high as 508 (range B). The 480-volt equipment in your facility may not reach or exceed 500 volts but we always err on the side of caution and recommend to our clients to use class 0 rubber insulating gloves to ensure worker safety when working on or near this equipment.

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Q8. How does reducing clearing time reduce arc flash hazards?

Clearing time is the amount of time it takes a circuit protection device to clear a fault. An arc flash occurs when a short circuit (fault) takes place inside of equipment. Once started, the flash will continue to expand until the upstream overcurrent protective device, such as a circuit breaker or fuse opens the circuit shutting off the supply of energy. If a fuse that blows quickly or has what’s called a short clearing time is installed in the circuit, the subsequent arc flash will be small because it doesn’t have time to grow. If the circuit relies on a fuse that has a long clearing time the flash could expand to a dangerous level.

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Q9. How many hours of training  does NFPA 70E require?

Although NFPA 70E contains guidance concerning the training of workers who are exposed to electrical hazards, there is no requirement for the length of time the training is required to take.

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Q10. Does Safety Training Qualify or Certify my Employees?

Most electrical safety training companies provide students and employers with a certificate of completion if the student successfully completes their course. These documents simply identify that the employee has satisfactorily completed safety training, this is not a qualifying or certifying document. However, these certificates could be kept with other required training records as proof employees have completed a formal electrical safety training program.

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