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PLASTIC CONDUIT

Description: This is rigid, usually gray, and it comes in rigid pipe sizes.

Buying information: It can be used underground, but will not take a damaging blow the way metal will. It is cheaper than metal conduit.

How-to hints: If you want to change direction with conduit, you can obtain fittings for the job just as you can for EMT and rigid pipe. Plastic pipe is secured to boxes with its own fittings, or if the boxes are plastic, it can be glued in place. A separate grounding wire must be used since the plastic is nonconductive.

CABLE/CONDUIT STRAPS AND STAPLES

Description: These come in various shapes: Two-hole straps are U-shaped with extending parts at the ends of the legs of the U and holes for fastening: one- hole straps are U-shaped with one extending part that has a hole in it for fastening. Staples are also U-shaped with the legs of the U sharpened.

Buying information: Cable normally runs inside house walls and ceilings, and to a lesser degree so does EMT and plastic conduit. But when any of these is in the open, it needs to be held secure -- a job for cable/conduit fasteners.

The most popular fastener is the staple. It is available in various sizes and will accommodate cable up to No.1 0 wire. Staples are driven in place with a hammer, but some people find this awkward and instead use the one-hole or two-hole metal cable strap that is placed over the cable, and then drive in nails to secure it. Straps make a neater job than staples, and can be shaped to fit more easily than can staples. One-hole straps cost less than the two-hole type.

You shouldn't use staples for conduit, EMT, or plastic conduit: use only straps.

Straps are available in various sizes. Select the same size as the conduit or cable. If you are using a 1/2-inch conduit, get a 1/2 inch strap, and so on.

How-to hints: Install staples over cable every 4 feet; also install one within 1 foot of a junction box to guard against the conduit pulling free.

For fastening thin-wall, heavy-wall, or plastic conduit, straps, as mentioned, are best. Use these every 5 feet, and one within 1 foot of a junction box.

=== To make fastening greenfield and heavy-wall conduit, EMT, or plastic conduit easier to install and more secure on various types of siding, follow these tips:

Brick and other masonry: A plastic or fiber plug with a No. 10 sheet metal screw works well. Plastic is preferred by many electricians: it's cheaper than fiber and grips the screw better. To use a fiber or lead plug, use a 3/16 inch carbide bit to drill a 1 1/4 -inch-deep hole. Insert the plug, lay the conduit in place, then the strap, and turn the screw through the strap hole (or holes, if you use the two hole type) into the plug.

Cedar or asbestos cement: Use No. 10 sheet metal screws; they grip much better than regular wood screws because their threads go all the way up to the head.

Aluminum and metal siding: Punch a hole with an awl, then use a sheet metal screw. The method works on up to 3/16-inch gauge siding.

Wood: Use a sheet metal screw. It will hold better than a regular wood screw.

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