Popular Woodworking 2006-11 № 158, страница 31
Circuit analyzer power on. The probes are touched to a hot line and the ground, causing the indicator to light. Also for checking DC/AC voltage, outlets, motors, appliances and fuses. ■ Volt-ohmmeter, or multitester - Use to test a variety of conditions, including voltage, low-voltage current, resistance to ohms and continuity. Also for checking outlets, fuses, wires, plugs, motors and electronic circuits. ■ Circuit analyzers - Use to determine if there is power to a receptacle, proper grounding or if the wiring is correct. There are more sophisticated circuit analyzers that can check from the receptacle back to the service panel for voltage drops or for current leaks. Electrical Supplies Be certain that the electrical supplies you select are approved or meet local building codes. If you aren't sure about this, then it would be best to consult certified experts. There are too many choices - guessing which part or wire size to use is the wrong approach. The term "wire" typically refers to a single strand of conductive metal enclosed with insulation. The term "cord" is used to refer to stranded wires protected by insulation. It can consist of two or three stranded wires within the insulation and is used for appliances, lamps, etc. "Cable" has two or more color-coded insulated wires that are protected by sheathing. In the United States the colors of the individual wires are: black or red is the power, or hot wire; white or gray is the neutral; and green (or green with a yellow stripe) is the ground wire. Sometimes the ground wire is a single uninsulated copper wire. Wire Size and Type Use the correct wire size and type when upgrading an electrical system. Local codes will specify the types of cable and cable conduits permitted in your area. Here are the common wire types: ■ Type NM (nonmetallic), has thermoplastic insulation and is capable of withstanding a wide range of temperatures. It's used for most household circuits. ■ Type UF (underground feed) is waterproof and is used for damp and outdoor locations. ■ Type USE (underground service entrance) is used for underground or overhead service entrance and direct burial to garages and workshops. ■ Type THW is used for outdoor hanging or indoor conduit as service-entrance cables and for conduit to a subpanel. Of the above types, NM cable is the most common plastic-sheathed cable. It's often referred to as Romex, a trade name. The sheath is usually moisture-resistant and flame-retardant. Normally, there are insulated power wires and a bare ground wire inside of the sheath. Armored cable, also referred to by the trade name BX cable, has an outer armored layer, usually flexible galvanized steel, that often contains two or three wires wrapped in paper. Conduit is usually either galvanized steel or plastic pipe. It's generally available in 1/2", 3/4", 1" and l^V diameters. The correct size to use in your woodshop depends on the diameter and number of wires inside the conduit. Wire Size Wire size is extremely important when upgrading an electrical system. Standard reference numbers, usually printed on the outside of wire insulation, are based upon the American Wire Gauge (AWG) system. Gauge numbers are inverse to their size; that is, the smaller the number, the larger the wire diameter. The maximum current that a wire Typical Tool Amperage Draw 10" Cabinet saw 8.3 @ 240v
Circular saw 13 For tools not included on this list, the National Electrical Code sets minimum amperage capacities: ■ Small appliances - 20 amperes ■ General lighting - 15 or 20 amperes ■ Stationary tools - multiply the machine's amperage by 125%. (A 15-amp planer will require 1.25 x 15 = 18.75, or a 20-amp circuit.) popularwoodworking.com i 31 |
