The first thing to understand is that a circuit breaker can have tripped off even when it looks like it’s in the “ON” position. This is because a circuit breaker will sometimes trip off internally, without the "ON/OFF" handle flipping to the “OFF” position.
This is what to do when you have a loss of power that you suspect may be caused by a tripped circuit breaker.
1. Shut down any computer equipment that may be affected by a loss of power.
2. Go to your circuit breaker panel and firmly flip the first breaker OFF and then back ON again.
3. Do the same thing with each circuit breaker until you have flipped all of the circuit breakers OFF and then back ON again.
4. Now check and see whether the device that didn’t have power is now back on again.
5. If your power has been restored… you’re done! If your power is still out, it’s time to call an electrician.
Note: About 25% of all electrical power problems can be solved using the above technique. Good Luck!
More Technical Stuff About Circuit Breakers
Inside most circuit breakers there are two types of protection: One is thermal. The other is magnetic. The thermal strip measures heat build-up caused by overloading. When it reaches a certain temperature, it will shut off the breaker. The magnetic coil measures sudden increases in current (such as a short). At a predetermined limit it will shut the breaker off. Older breakers sometimes have only one of these features. For maximum protection, a breaker with both types of protection is recommended.
There are usually three spots on the outside of a breaker that show wear. If the "ON/OFF" switch (located at the top) has broken off or is loose, we recommend the breaker be replaced. Next is the load lug. If it is burnt or abnormally loose, we recommend the breaker be replaced. Last, and most common, is the stab. The breaker stab is what makes contact with the bussing in the panel (the bussing carries the power throughout the panel). The stab connects to the bussing through friction and spring tension. The spring tension, over time, may break down. If so, arcing or burning may result. If the stab has become burnt, discolored, or is abnormally loose, we recommend that the breaker be replaced and that the bussing in the panel be checked.
NOTE: It is possible for a breaker to appear OK in regard to it's outward appearance and its capacity to carry continuity, but still be questionable, bad, or intermittent. The opposite may be true as well. A breaker with a poor outward appearance may be perfectly safe and structurally sound. Therefore a decision to replace a breaker should not be based solely on appearance, continuity, age, etc. A good electrician can recommend the proper course of action based on taking into account all the relevant factors like those at The Electric Connection.