| | | | | is because the absence of a third prong or |
| What is Knob and Tube Wiring | | | | "grounding" prong is meant to prevent people |
| | | | | from plugging in equipment that needs to be |
| Knob and tube was one of the most hazardous | | | | grounded but instead most people break off the |
| wiring methods ever used because it is an | | | | grounding prong of an extension cord or power |
| ungrounded system. What does this mean? | | | | tool making it extremely unsafe. |
| Electricity begins at the circuit breaker where it | | | | |
| flows through the hot or "ungrounded" conductor | | | | Another way this may be corrected is by installing |
| and comes back on the neutral or "grounded" | | | | a ground fault receptacle, which measures the |
| conductor completing its path. This system | | | | current going through the plug itself and will trip if |
| works well in theory until you become a path to | | | | there is an unbalanced current, protecting the end |
| ground. | | | | user. While this is the safer "quick fix", the |
| | | | | potential homeowner is still left with a knob and |
| Recently, an alternate path to ground is required | | | | tube system. |
| by either using the outer metal sheathing of wire | | | | |
| or conduit or by placing an actual ground or | | | | Some may think that they are safe because they |
| "grounding" conductor within the wire assembly. | | | | have installed GFCI receptacles but another |
| This provides an alternate path to ground tripping | | | | problem exists. When knob and tube circuits run, |
| the circuit breaker disallowing YOU to become | | | | they would pull a neutral wire from whichever |
| that path. | | | | circuit was closest. This means is that there is |
| | | | | an abundance of current overloading the neutral |
| This might not sound very likely, but it is actually | | | | conductor that is not connected to a circuit |
| not hard to accomplish. If you are in your | | | | breaker allowing that conductor to overheat and |
| basement and pull the pull chain of an ungrounded | | | | not open the circuit. |
| light fixture, you can easily become the path to | | | | |
| ground. The same can happen with any | | | | Excessive heat to a conductor will cause the |
| ungrounded light switch or receptacle. | | | | insulation to breakdown. Over time, the outer |
| | | | | coating will become frail and brittle exposing the |
| The National Electrical Code permits ungrounded | | | | bare copper conductor. Once this happens, it is |
| receptacles to be two-pronged instead of | | | | only a matter of time before you need an |
| three-pronged. The reason the code allows this | | | | experienced electrician. |