Although it would be nice to be factory-trained on every piece of equipment (and have electrical troubleshooting fundamentals decision-tree or flowchart, too!), reality hands us a different situation. You may be tasked with troubleshooting a piece of equipment or a system that you haven’t seen before.
Caution: Before proceeding, make sure you are qualified (per the OSHA definition) to service that category or class of equipment.
For example, you have standard training as an electrician, so you can troubleshoot a 120V receptacle problem. But your boss wants you to figure out why a 400A, 480V circuit breaker is malfunctioning and repair it. You may be qualified to determine the problem is in the breaker, but you aren’t qualified to actually work on that breaker.
Here are some Electrical Troubleshooting Fundamentals
The first step
The most fundamental step in troubleshooting is to check the power supply. For example, a motor won’t start. Is the disconnect open? If the disconnect is closed, you’d probably want to check the motor overload devices (typically “heater” strips). If they look OK, then you’d use your DMM to see if there’s power to them, and, of course, on the motor side of each one.
If there’s no power, employ the “divide and conquer” strategy to find the power problem. In this situation, for example, you’d go to that disconnect and see if there’s power to it. If so, do a visual inspection before closing it so you know (with very high probability) there will be power coming from the disconnect.
If there’s power at the disconnect, then you’ve saved yourself a wasted trip to the breaker that’s in a panel halfway across the plant. The problem is between the disconnect and the overload device.
If there’s no power at the disconnect, then you’d go to the branch circuit breaker and check it. If the breaker is supplying power, the problem is between there and the disconnect.
Read more about electrical troubleshooting fundamentals at ecmweb.com