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Any addition to your home is likely to need electricity. Electrical codes commonly require receptacles every 12 feet, as well as a light switch near the room entrance. If a nearby house circuit is not heavily used, you can extend it to the addition. But don’t put more than a total of 12 outlets on a 15-ampere circuit or more than 16 on a 20-ampere circuit. When the power required exceeds these limitations—or when you plan to use an appliance that draws at least 7.5 amperes— you will have to add a new circuit to your electrical system. if the new power source is intended for lights only, a 15-ampere circuit will do; if it may have to serve a small appliance such as a toaster or space heater, a 20-ampere circuit is normally required. Unless the addition can be heated by the house furnace, also plan for one or more baseboard heaters, each with a separate 20-ampere circuit. Checking Available Power: Be fore adding a circuit, calculate the total electrical load of your house in watts and amperes to be sure you have enough unused power coming into the service panel. If you do not, have an electrician install a new panel for a larger load. When a pan el has adequate capacity but no room for a new circuit, install a sub- panel for the addition. Preparing for the Job: Begin by drawing a circuitry plan for your addition, showing the locations of electrical boxes and devices as well as routes for wires. You may have to submit this plan when you apply for an electrical permit; you can also use it as a reference when shopping for materials. Buy cable with 14-gauge cop per wire for 15-ampere circuits, 12-gauge for 20-ampere circuits. Most connections between two cables with 12-gauge wires require a 2.5-inch-deep rectangular outlet box. Get an adequate supply of jumper wires and wire caps, and be sure that any switches you purchase have grounding screws in stalled by the manufacturer. Roughing In: Start wiring your addition when it’s weathertight but before you put in insulation or wallboard; the wiring done at this roughing-in stage will have to undergo an inspection, the first of two. Mount the wall and ceiling boxes, run cable from the service panel to the box and heater locations, and make up the ground connections in each box. Then call the electrical inspector for the rough-in inspection. Finishing Work: After you have laid finish flooring and installed the wallboard, wire the switches, receptacles, and light fixtures; secure them in the boxes; and screw on the cover plates. Install and wire electric baseboard heaters. The last step is to make the connections at the service panel. When this has been done, arrange for the final inspection. CAUTION---Only the electric company can fully shut off power to the service panel. If, as an alternative, you choose to trip the main breaker, be aware that this does not completely kill power within the service panel. Always exercise extreme caution when working around a service panel. TOOLS:
MATERIALS:
SAFETY TIPS --- Protect your eyes with safety goggles when hammering or operating a drill. Mapping circuits. 69a--- On a piece of graph paper, make a plan of your addition and mark the location of each switch, receptacle, lighting fixture, and electric heater. Then draw cable routes between the connections for use as a guide in wiring the circuits. The diagram above shows two circuits: A 240-volt circuit goes to a wall thermostat and then to a base board heater; a 120-volt lighting circuit enters the addition at a receptacle near the door and goes around the room to each receptacle, then on to the light switch and the overhead light. MOUNTING OUTLET BOXES Nailing a box to the framing. 69b--- A metal box with a cleated flange is well suited to addition framing. • Mark the height of a box on a stud. Receptacles are commonly set 12 inches above the floor and wall switches at a height of 48 inches, but you can position them to ac cording to your needs. • Align the box so its face extends out from the edge of the stud just enough to accommodate the planned thickness of the finished wall. Tap the cleat into the stud to hold the box in position while you nail it. For an overhead light, round or octagonal boxes with side- mounted flanges can be fastened to a joist. If you need to mount a box between joists, install a hanger bar and screw the box to the bar. RUNNING CABLE TO THE ADDITION 70ab--- Wiring the addition from below. When creating a path for a planned circuit, drill -inch holes through any obstacles. Most codes require holes to be at least 1 inches from the edges of framing members. • For an addition with a crawlspace, drill a hole through the sole plate and subfloor near the first receptacle. • Drill a second hole through the end or header joists of the house and the addition. • Fish cable from the service panel into the addition, leaving a 2-foot tail of cable at the panel. • Where cable runs horizontally through studs or joists on the way to the addition or within the addition, no extra sup port is needed; elsewhere, anchor it with staples or clamps at least every 44 feet. Wiring the addition from above. For an addition that does not have a crawlspace, run cable from overhead. • Drill through the top plates of the addition and the exterior house wall. If you are drilling into a finished second floor, try to go through the wall into a closet or a cavity around plumbing pipes. When neither is available, drill into an interior wall; then, from the attic, drill down through the top plate into the wall. • Fish cable from the service panel, across the attic, and into the addition, anchoring the cable as explained at left. WIRING THE BOXES 70c--- Fastening cables to boxes. • With a screwdriver, remove a knockout from the box. • Remove 8 inches of sheathing from the end of a cable with a pocket knife, then strip 4 inch of insulation from the ends of the wires. • Clamp the cable in the box. To secure a cable in a junction box, use a two-part cable connector consisting of a lock nut and threaded clamp. • Secure the cable to the framing with a staple or clamp with in 12 inches of the box. • Repeat for each additional cable entering the box. LOCK NUT Grounding boxes. • For a switch or receptacle, join two green jumper wires to the bare cable wires with a wire cap. Connect one jumper to the box ground screw and save the other for later attachment to the grounding terminal—usually green—of the receptacle or switch. • Fold all of the wires neatly and push them into the box to protect the exposed ends from paint or joint compound. Most light fixtures also require a jumper wire. Prewired baseboard heaters need no connections at this stage. Simply bend an 18-inch tail of cable into the room so that the cable won’t be covered when the walls are finished. MAKING SERVICE-PANEL CONNECTIONS 1. Attaching electrical devices. After installing wallboard, connect the wires to the devices. Hook up a 240-volt electric heater as follows: • Clamp the cable to the built-in box with a two-part cable connector, then mount the unit on the wall. • Fasten the bare cable wire to the grounding screw in the heater box. • Connect the black wire of the cable to a black heater wire; recode the white cable wire with black tape, then connect it to the other black wire. Connect light fixtures, receptacles, thermostats, and switches so that black wires attach to black wires or brass terminal screws, white wires to white wires or silver terminal screws, and bare or green wires to green terminal screws. 2. Grounding new circuits. 72a--- You may prefer to have the electric company turn off power to the panel before you work on it. Some companies require a separate inspection before restoring power. If you don’t have power turned off, the insulated main wires and the lugs to which they attach remain live as you work—be careful. In either case, proceed as follows: • Turn off the main circuit breaker. • Open a knockout for each new circuit. • Pull the cables into the service panel and secure them with two-part clamps. • Strip the sheathing from each cable beginning about inch after it enters the panel. Re-code the white wire of a 240-volt circuit with black tape. • Screw the bare wires and white wires of 120-volt circuits to the ground/neutral bar of the service panel. • Connect the bare wire of a 240-volt cable to the bar. CAUTION---Don’t connect the recoded white wire of any 240-volt circuit to the ground/neutral bar. 3. Installing the circuit breakers. 72b--- Keep the power off at the panel. For a 120-volt circuit, snap the terminal end of a single-pole circuit breaker under a tab in the panel, then snap the breaker into the corresponding bus bar fitting. Fasten the black wire to the terminal screw. For a 240-volt circuit, snap a double-pole circuit breaker into place in the same way. Then screw the black wire to one terminal and the recoded white wire to the other. When the work has been completed, restore power to the panel. |
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Tuesday, April 1, 2014 1:25 PST