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Electrical work involves following the National Electric Code and many other standards that vary by state and by city. In addition, it is often necessary to work in reduced spaces where it may be difficult to connect equipment properly. The following are some of the most common mistakes electricians make.
Cutting wire properly reduces waste and the material costs of a project. However, you should not overdo it: wire that is cut too short provides poor electrical contact due to the resulting mechanical tension, or may be impossible to connect at all.
A better approach is to pull wire through conduit before cutting it from the roll. That way you can cut a wire run of exactly the required length. With this approach there is no waste, and you still have enough clearance for a proper connection.
When a receptacle is connected properly, the narrow slit leads to the hot wire and the wide slit leads to the neutral. To accomplish this, the hot wire must be connected to the yellow screws and the neutral must connect to the silver screws.
Although alternating current reverses polarity 60 times per second, many pieces of electrical equipment interrupt the power supply at the hot wire. If connected to a receptacle with reverse polarity, many internal components will be exposed to voltage even when the device is not operating. This makes equipment more vulnerable to ground faults, which would not occur if connected to a properly-wired receptacle.
Conductors are color-coded to simplify future modifications and maintenance activities. If an electrical installation is wired following a color chart, it is possible to tell the voltage and phase of a conductor just by looking at its insulation color. In the US, the following color convention is used:
Installations under 240V
Red in wye connection, orange for high leg in delta connection
Green, Bare or Green/Yellow Stripes
However, there are cases where insulation color convention is not followed, making installations much more difficult to service. Contractors and maintenance personnel can no longer rely on the color of conductors to determine their voltage and phase, making maintenance and modifications much more time-consuming. There is also a higher chance of electrical faults, since anyone who assumes the wiring is coded by insulation color can end up connecting equipment to the wrong voltage.
There are cases where the grounding conductor is easier to access than the neutral conductor, and contractors may be tempted to take the easy route and use it instead, given that it’s also at zero volts. However, this overlooks the fact that the neutral conductor is intended to carry current normally, while the grounding conductor is expected to provide a low-resistance path to ground that does not carry current under normal conditions. In addition to being a code violation, using the grounding conductor as a neutral diminishes its ability to provide grounding in the first place, since it will now carry current while having a small voltage difference with respect to the grounding busbar.
Junction boxes protect electrical connections from tampering, rodents, sudden movements or anything that may loosen them or pull them apart. Junction boxes also provide protection for the building itself and its occupants, minimizing the risk of fire due to localized heating or sparks. Electrical connections outside of a junction box are against code and a potential source of accidents. If a fault associated with a connection with no junction box occurs, solving it can be very difficult because the location is not evident.