A short circuit study is typically part of the arc flash study.

Has your company / client ever had equipment with an inadequate short circuit interrupting or withstand rating?

• Yes
• No

Commonly, the main breakers of LV distribution panels - original breakers, usually left untouched since building inception, for older buildings, where utility fault levels have increased over time.

We find them in maybe 60% of our studies.

The leading reason, is that nobody considered what fault current might be available, except at service entrances.

We completed a survey for a customer. One of our findings was an over-dutied service entrance. It was rated for 18 kAIC at 600 volts, but the fault current was 35 kAIC. We addressed this issue with the customer, but he chose not to correct the problem. Two years later, they had a fault on an 800 amp branch circuit fed from this service. The breaker failed and took out two distribution sections with it.

When we conduct studies for clients, we often find equipment with inadequate ratings. It's just the nature of the study. What we have run into from time to time, is a client sometimes expects a study to be more of a blessing of their system. When they see that we point out inadequate equipment, the situation sometimes become a bit confrontational. We then spend a lot of time hand holding and trying to explain to them what the problem is. They see inadequate equipment as a need to spend money and a possible liability if they don't correct it and they are not happy.

I wonder how many others have had this situation?

Our plant study revealed fault current significantly in excess of the 480V switchgear rating - something like 70kA capability against a 50kA rating. Engineered remedy was to install oodles of buss bracing, and to replace the breakers. HRC then reduced from Dangerous to 3.

I find this situation in large plants with older infrastructure, or plants that were expanded due to high demand for their products. Probably exisits in 40% of the plants we have studied so far (studied about 125 internally). We have had great support from the top in our Company to correct these situations as they are found, but it isn't always appreciated by the lower levels of management who sometimes see it as a liability, downtime, and needless expense (It lasted for 30 years, why is it bad now?). Training through creation of tail gate talks, powerpoints in annual meetings, and support of upper management can really help, but it takes a lot of work and a "Champion" in your Company to drive it.

Very common, we have seen a huge demand for high AIC rated versions of older breakers from facilities that run into this issue after a study. At least it is usually a pretty simple fix.