The trigger wire is used to activate all the interconnected smoke detectors the instant one detector senses smoke or fire. Red can also be used as a “signal” or “trigger” wire in three-wire interconnected smoke detector applications. If your new ceiling fan has a light, a red wire from a second switch in the same wall box can provide switched power to the fan’s light. When installing a ceiling fan, you’ll often find that the black wire coming from the wall switch provides switched power to the fan motor. Red or orange can also be used as a second “switched” power wire in a 120-volt application. In that wiring scheme, assume the black and re-marked white wires are live. You’ll find black and red or orange wires connected to 220-volt appliances like electric water heaters, well pumps, and older electric ranges. However, those same 220-volt appliances can be wired with a black and white wire, where the white wire had been marked with black or red tape at both the appliance and in the main panel to indicate that it has been re-purposed as a current-carrying wire. Red or orange wires are often used to provide the secondary phase voltage in a 220-volt application.Īlways assume that a red or orange wire (in addition to the black wire, which provides the primary phase voltage) is live. Black wires are used to provide power in the circuit.Īlways assume black wires are live. The new color should follow the common industry practices outlined here, but do be sure to include a notice at the main electrical panel or sub-panel indicating what the markings mean. White and gray wires may be repurposed as current-carrying conductors if they’re marked at both ends with tape or paint. The 2011 National Electrical Code required a neutral in every switch box to accommodate new devices like motion sensors, occupancy sensors, home automation switches, and dimmers. If your switch box doesn’t have a neutral wire, find a device that doesn’t require a neutral or have the box rewired by a professional electrician. White and gray wires are normally used as neutral conductors. Don’t make this mistake. If you see a ground wire connected to a current-carrying screw or terminal on a switch or outlet or to a white, black, or any other color wire, stop immediately and call an electrician to sort it out. Still, many older homes don’t have neutral wires, and some inexperienced do-it-yourselfers will connect the white neutral wire from a new switch to the ground conductor to make do. Photo: Green, green with a yellow stripe, and bare copper wires can only be used for grounding purposes.Ī ground wire can never be used as a neutral, even though it connects to the same bus at the main panel-that’s a huge safety violation that can cause electrical shock, serious injury, or death. That’s allowed by code as long as the wire is marked with red or orange tape or paint to alert future service people, electricians, or knowledgeable do-it-yourselfers that the wire is not a neutral but rather a current-carrying conductor. Since those appliances don’t require a neutral but use two current-carrying conductors and a ground wire, an electrician may repurpose the white to carry the secondary phase (also called a “secondary leg”) of the 220-voltage. However, when sized appropriately for the load, two-wire armored cables can also be used to provide power to 220-volt appliances like a water heater or well pump, which is where things get tricky. The hot or “live” conductor sheathed in black typically carries power to a 110-volt light or receptacle, while a neutral conductor would carry energy away and a bare copper ground wire can conduct any excess energy that might otherwise be a shock or fire hazard. In this case, your water heater is probably wired with two-wire flexible armor-clad “BX” or “MC” cable-that’s a factory-made cable with a metal jacket protecting a black, white, and bare copper wire. A: You’re right, white sheathing does generally indicate a neutral wire, but it’s not always so simple to decipher.
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