Electrical equipment is a large part of our lives, and we often don’t realize how much we rely on it. Recently, I was attending a major competition for my daughter’s all-star cheerleading team, and all the down escalators in the building went out of commission. To most people, this wasn’t a massive inconvenience because, as the late, great comedian Mitch Hedberg pointed out, an escalator never really fails—it just becomes stairs. But it got me thinking about how we treat our electrical equipment after installation. Do we perform the proper maintenance to keep it running? Or are we just one event away from the equipment shutting down?

This also reminded me of a saying I have seen when it comes to maintenance: “Schedule time to maintain your equipment, or your equipment will schedule it for you!” So, what does maintenance have to do with safety? The short answer is, everything! 

By now, of course, many of you have heard of NFPA 70B becoming a standard instead of a recommended practice for electrical equipment maintenance. But you might still be wondering about the direct tie to safety. 

Let’s look at one of the most important safety devices of all, the overcurrent protective device (OCPD). This device is installed to shut the circuit off when there is a short-­circuit or ground-fault and to keep the electrical system from burning the building down when it overheats the conductors during overload conditions. So, the OCPD is a major player when it comes to safety of people and property. Wouldn’t it be nice to know the OCPD will perform as designed when we need it to? We might not be able to be 100% certain, but with a little TLC over time, we can keep the risk of OCPD failure as low as possible.

Arc flash labels and risks

Do you remember the last time you looked at an arc flash label on an MCC or switchboard? You read the label and saw it gave you the estimated amount of incident energy that would be released during an arc flash. Most likely, you used this number to select the appropriate level of arc-rated PPE to wear when verifying absence of voltage to create an electrically safe work condition. But did you understand what that number is based on? Yes, a ton of data must be collected to determine the incident energy and the arc flash boundary, but one major component is the clearing time of the OCPD. 

Recently, a colleague that specializes in performing arc flash studies shared a series of calculations they had performed to show just how important maintaining clearing time was. The first calculation showed the equipment at the point of work when everything functioned as expected to have an incident energy of less than 1 cal/cm². However, when the branch circuit OCPD couldn’t clear the arc flash, either because the device failed or just didn’t open as fast as the upstream feeder device, the incident energy jumped up to nearly 2 cal/cm². 

While this wasn’t a massive change warranting an immediate plant shutdown and emergency repair, it was concerning because it showed a trend: if there was no maintenance performed on the branch circuit OCPD, it is likely that the feeder OCPD had not been maintained either. And what happened if the feeder device failed to clear the fault before the service OCPD handled it? Well, now the clearing time had gone from under 2 cycles to nearly 2 seconds because of the service OCPD, this local arc flash didn’t seem like such a major event since the fault current was lower due to length of circuit, and it was an arcing fault. The incident energy now was nearly 50 cal/cm² and a far cry from what we started with.

Minor inconvenience to big problem

This is a direct result of a lack of maintenance. Sure, the escalators at a cheer competition might be a minor inconvenience when they break down from lack of maintenance, but how long before that minor inconvenience becomes something much more serious? If something that obviously requires regular maintenance is down, what does that tell you about the maintenance of the rest of the building’s electrical systems? 

The scary thing is that in our travels for cheerleading, it has become a joke that, “Is it really a cheer competition unless an escalator breaks down?” Is it really an emergency until the incident energy has gone from less than 1 cal/cm² to nearly 50 cal/cm²?

Electrical safety is the delicate balance of lowering the likelihood of occurrence and the severity of injury. Maintaining electrical systems is key to achieving it.

Until next time, stay safe and remember to always test before you touch! 

Learn more about sizing OCPDs in "What Are We Protecting From?"

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