HOME CLINIC — At Work on Electric Boxes Between the Ceiling Joists -

HOME CLINIC - At Work on Electric Boxes Between the Ceiling Joists -

HOME CLINIC; At Work on Electric Boxes Between the Ceiling Joists

Published: June 21, 1992

LARGE-BLADED ceiling or paddle fans are easy to connect to existing ceiling wiring like that of an overhead light. But to comply with electric codes in many communities, the electrical box containing the wiring, and to which most fans are attached, has to be a special kind.

Using a code-approved box makes a fan less likely to fall from the ceiling. Unfortunately, installing such a box to replace an existing unapproved box usually makes the job of installing a fan more difficult.

There are two types of electrical boxes approved for use with ceiling fans. For replacing an existing box that is mounted against a ceiling joist, a box having long bolts attached to it for fastening the fan is used. The box is attached to the joist with lag bolts, which anchor the box more firmly than nails or screws. Be sure the box is labeled for fan support and carries a mark like that of Underwriters’ Laboratories.

For replacing an electric box suspended from a hanger bar, a metal bar that spans the space between two joists, or for use when a joist-mounted box cannot be easily removed, use a telescoping fan brace. That is a sturdier version of a hanger bar.

Labeling should be similar to that described above. Included with the brace should be an electrical box designed for it and hardware for connecting the box and the fan to the brace.

Although mounting instructions come with approved electrical boxes and with fan braces, the homeowner generally has to determine how to gain access to the existing box, remove it, reconnect the existing wiring inside the new box and patch the area after the new box is installed.

Check with the building inspector to make sure that the code allows nonlicensed people to work on the tasks. Begin by turning off the power to the ceiling fixture by tripping the circuit breaker or removing the fuse controlling it at the service panel. The panel, or fuse box, is usually in the basement, utility room or garage.

Carefully remove the fixture by lowering it and unscrewing the plastic caps joining its wires to those in the box. Separate the wires to free the fixture. Touch only the wires’ insulated parts, never the bared ends.

Set the fixture aside and turn the outlet’s wall switch to on. Using a circuit tester, a small inexpensive bulb with two wire probes, touch the tester’s probes to all possible combinations of the outlet’s wires and the box. The tester should not light in any position. If it does, power still reaches the outlet. Do not proceed until it is turned off.

Afterward, if there is access to the ceiling box from an unfloored attic above it, the box can easily be replaced from there. But if flooring is present, either cut through it or work from underneath.

To cut into flooring above a ceiling box, locate the correct spot by measuring or, if possible, by drilling through the floor from below. Next, examine the flooring for nails, which indicate the positions of joists underneath, and mark out a rectangle centered on the box location that extends between the two joists on either side of the box and is about 14 inches wide.

Drill through the floor at the corners, and cut through the flooring between the holes with a compass saw or saber saw. Be careful not to strike any cables that may be attached to the sides of the joists. Save the flooring for reinstallation.

Pry loose any staples holding cables near the box, and avoid nicking any of the cable insulation. From underneath the box, unfasten any clamps inside that hold the cables entering it. Then push the ends of the cables out of the box or pull them out from above.

Finally, pry the box away from the joist if it is nailed or loosen any screws holding it. If the box is attached to a hanger bar, pry off or unscrew the bar from between the joists.

Mount the new box or telescoping brace as close as possible to where the original was installed. Then feed the cables into it and install new staples to replace any that were removed.

Cut two strips of 2 x 4 lumber as wide as the opening and screw those against the joists, so that their top edges are flush. Use four shorter strips if a brace is installed.

Connect the fan to the ends of the cables in the box by following the manufacturer’s instructions. After testing to make sure that the fan works, reinstall the flooring that was removed earlier by nailing it to the strips.

To replace a ceiling box on a hanger bar with a telescoping brace from below, you may be able to install the brace by inserting it through the hole in the ceiling created by removing the existing box from the bar. Instructions that come with most braces describe the procedure.

Where this is not possible, and when replacing a box attached to a joist, outline and then cut out a rectangle of ceiling material roughly similar to the area of flooring described above, but three-quarters of an inch longer at each end so that the ends lie along the undersides of the joists.

Remove the wiring and existing box by following the procedures already described. Then install a replacement box, reinstall the wiring and make a patch for the ceiling out of new drywall. The patch has to have a hole in the center for the box. Fasten the patch with drywall screws to the undersides of the joists.

Temporarily install and test the fan. If it works, remove it and finish the patch by applying drywall tape and two or three layers of joint compound around its edges. The compound has to dry between coats. Sand and paint, and then reinstall the fan.

Drawings showing how to install ceiling fans.

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