Electrical Troubleshooting Quiz — November 1, 2022

You work for a small electrical service company. You have been sent to a residential job site to replace incandescent lights with LED lights and to install LED compatible dimmers. This work is in two bathrooms, the living room and the kitchen. The kitchen and living room were no problem, but when you opened the circuit breaker listed (on the panel directory) for the bathroom lights, the lights stayed on. The owner doesn’t want you to just flip breakers around until you find the right one. It says you should be able to work it hot, using an insulated screwdriver. How do you solve this?

Simple tests

In theory, you could work it hot; you can wear insulated gloves and use insulated tools. If you disconnect the power side of the switch first and reconnect it last, you halve the risk of electric shock instead of doing it the other way around. But there are three big problems with this:

  1. There is no compelling reason to work hot, only the convenience of the owner.
  2. If the circuit breaker has failed and its mode of failure is that it does not open, you will be leaving a dangerous condition behind.
  3. If the circuit breaker works fine but the directory is wrong, you are also leaving a dangerous condition behind. Not everyone who opens a home circuit breaker before exposing conductors tests those conductors to make sure they are de-energized.

You may just need to fix the directory. Draw it on paper and through testing correctly identify the circuit(s) in question. There is no need to remap the whole thing and further annoy the owner. Just find which circuit powers the lights, then identify which circuit it is swapped with in the directory. Also note that it is impossible for the 15A circuit breaker of these lamps to have been swapped with the oven circuit or the HVAC circuit. Unless something epically silly happens, you can limit your investigation to 15A circuit breakers.

Let’s say the directory tells you that circuit breaker 6 is for these lights. The most likely problem is that the labeling is swapped between two adjacent breakers. If circuit breaker 4 says bathroom outlets, try running it to test the lights. Or it could be breaker 8. This simple test can provide a quick fix. But let’s say no.

Since this is a residential application, it is very likely that you are working with a distribution center rather than a distribution panel. The difference between the two is that with a distribution panel, the circuit breakers are bolted on; with a load center, they snap. If it’s a load center, you can easily remove and add a circuit breaker.

Note the position of each circuit breaker. When you’re done, you’ll need to make sure the circuit breakers are in the positions you found them. Normally this means that all are closed. But there may be a circuit breaker intentionally left open.

distribution panel

If you have a distribution panel, you will need to turn off the main circuit breaker. That means lots of extra steps, including setting up portable battery-powered lights. You will need to turn off all loads, including the HVAC. You will need to unplug major appliances (e.g. refrigerator), as well as any minor loads that are functioning normally.

You can use the same troubleshooting technique that we are about to look at for a load center, except that you must open the main circuit breaker so that you can unlock the circuit breaker for each individual circuit. And you will have to close the main to do the tests. It’s tedious, and if you’re not careful, it can be deadly. In this case, “cautious” means that you deliberately impose a method that requires checking that there is no current beyond the main line each time you place a tool on a circuit breaker.

load center

From a load removal perspective, this is almost as much work as preparing the main circuit breaker to open (as required for a distribution panel). However, in this case, you can leave the local lights on for the distribution panel to avoid all the hassle of installing the lights. And simple tests will be easier.

Make sure the lights and other loads are turned off in the bathroom and bedroom circuits, because you’ll be removing and resetting these circuit breakers.

Now remove the load center cover and identify circuit breaker 6. Your hands will not be near the live conductors, but wear your gloves anyway (the circuit conductor may be fed from another circuit, back-feeding the circuit breaker). Trip Circuit Breaker 6. Keep in mind that it is easy to inadvertently trip an adjacent circuit breaker and circuit breakers can be under load when this happens, which is bad. That’s why you close things in advance.

With circuit breaker 6 removed from the panel power strip, use your voltage tester on the conductor coming out of the circuit breaker. He should be dead, but what if he isn’t? If the conductor on the load side of the circuit breaker is still live, that circuit is crossed with another, probably at a switch or outlet. This is unlikely to happen during construction, so ask the owner about anything added or changed. You may be able to spot “homework” from visual clues such as a bent wall plate or a loose container. If not, you will need to methodically check behind each wall plate until you find the problem.

If the driver has no power, try running the lights.

  • If they came on before but don’t come on now, it’s the right breaker. It just won’t open, so it needs to be replaced. The 15 A circuit breaker typically used in this application costs less than $10; make sure the replacement is the same brand as the one you are replacing and is destined for a distribution center.
  • If they came on before and still come on, it’s the wrong breaker. Use your directory drawing, not the actual directory, to remap the breaker layout. Only when you have verified that you have a correct drawing do you push the update to the repository. Otherwise, you risk messing up the directory.


Once you have resolved the breaker exchange or faulty breaker issue, update the directory if necessary. Then you can put the cover back on the load center or panel. Once the cover is secure, check each circuit breaker to make sure it is in the correct position. Failure to do so could mean leaving occupants without heat or leftover food in the fridge.

Once you have completed the work originally planned for these bathrooms, perform a final check of the distribution center to ensure that you have set all circuit breakers to their original position. It may also be a good idea to reset the clocks for the owner. Make sure the refrigerator is plugged in and running. Leave small appliances unplugged, if they were, so the homeowner knows to do things like reprogram that fancy coffee maker so there’s hot java waiting in the morning.