Install pull rope conduit

Because differing soil elevations can add stress to a conduit when you backfill the trench. Important Note: the bottom of a trench can be soft or rocky. In such cases, remove the unsuitable material to a depth of at least 6-inches. Then replace with crushed rock, sand, or gravel as appropriate. Keep your excavation zone free from water during construction.

You want the static water level drawn down to a minimum of 2 feet below the bottom of excavations. This will maintain the undisturbed state of natural soils. For more information on dewatering, read here.

Important Note: control groundwater to prevent softening of the bottom of excavations. In very cold regions, install your conduit below the frost depth. This will help prevent the freezing of any water, which enters your conduit. Also, this prevents conduit damage from thermal expansion and contraction.

If your frost depth is 8-feet below grade though, the installation may not be practical. In these instances, first, check with your local jurisdiction in charge. This will help prevent the frost from penetrating any deeper into the soil. For example, use 1-inch rigid insulation. This insulation is equal to roughly one foot of regular soil depth. So if your frost line is 5-feet below grade, install the 1-inch thick insulation at the 4-foot mark. Next, a segment of your conduit will eventually rise above grade through the frost.

And this conduit segment will be prone to damage. This is why you find the most damage in the riser section of installations. So add expansion fittings on the vertical riser portions, to allow for settling. Important Note: temperature swings typically are much less underground. Also, the temperature swings underground are much slower. Extreme temperature swings cause conduit damage from expansion and contraction. This is one reason to add expansion fittings on vertical risers, to allow for settling.

When you have two or more conduits, install molded plastic spacers every six feet. Also, separate the conduits by 3 inches. This helps prevent the sagging and deforming of conduits. Refer to NEC section This can then cause ground fault issues. Flowable fill is a self-compacting, cement-type material used instead of compact fill.

The spacers allow you to get the compaction you need around your conduits. Proper backfill is critical to conduit installation work. This is the material used to refill a trench from the trench bottom to your conduit. You want to use granular material free from organic matter. The material should have a sand equivalent value of not less than And the material should conform to the following table:. Also, the coefficient of uniformity should be 3 or greater.

So clean natural sand or gravel is usable. But trench excavation is usable too, or a mixture thereof, with a sieve no greater than Use material consisting of either sand-sized particles or sand-sized particles mixed with gravel, crushed gravel, or crushed stone.

This is the backfill from the conduit to 12 inches above the conduit. Running NM cable inside conduit is not a standard practice and may not be allowed in all jurisdictions. The National Electrical Code NEC does not prohibit running NM cable inside conduit, but this installation is subject to conduit fill limits, just like insulated wire in conduit. Because NM cable takes up more space than individual wires, it's easier to exceed the fill limit with cable.

Also, cable is difficult to pull through conduit, due to the cable's size and the sheathing, so running cable in conduit typically is limited to very short runs that do not require standard wire pulling techniques. Also note that NM cable is not rated for outdoor, or wet, applications. It is never permissible to run NM cable outdoors or in other wet areas, even if the cable is installed in conduit. Pulling wires can be difficult enough through straight runs of conduit, but throwing a few bends and turns in the run increases friction, making pulling much more difficult.

That's when you use a lubricant. Wire-pulling compound is a non-conductive lubricant in either a gel or a slimy, soapy form that makes both the conduit and wires slick by coating the wiring, allowing it to slide through the conduit with relative ease. Apply the compound directly to the wires before pulling them into the conduit. Use the lubricant more heavily at the beginning of the pull and less so toward the end of the pull, as the interior of the conduit will become coated along its length as you pull.

Follow the manufacturer's instructions for proper application. A conduit mouse, also called a conduit piston, is a small cylinder of foam that is slightly smaller than the interior diameter of the conduit.

You use it with a shop vacuum. Tie a strong string, called a pull string, to the loop on the wire running through the mouse. Insert the mouse into the conduit on the end that is opposite to the end you will pull from.

The mouse goes in first, followed by the string. Fit the hose of a shop vac over the other end of the conduit, and turn on the vacuum until the mouse is sucked all the way to that end, then turn off the vacuum.

Pull the mouse out of the conduit and untie the string from the wire loop. Secure the string to the wires, and lubricate the wires, as needed. However, rewiring these conduits during repairs and renovations can be challenging. With conduit sometimes running hundreds of feet long, it can be difficult to ensure that wiring runs all the way through without getting caught. Fortunately, there are several methods to pull wire through conduit, and some of the best are covered here.

In these cases, you can simply attach the end of the old wire to the end of the new wire and use it as a pull wire, pulling the new line through the conduit. However, this is not always an option, especially when working with new conduit or severely damaged old wiring.

If you find yourself needing to pull wire through conduit, you can choose from multiple methods. Some of the best methods for pulling wire through electrical conduit are listed below, along with their advantages and limitations. The string method is the simplest technique for pulling wire through conduit and relies on a strong string called a pull string. The method works as follows:. This method works best on pieces of conduit that are short and straight.

Longer pieces of conduit or lengths with more curvature will require an alternative method. The mouse method is a variation of the string method that uses a tool called a conduit mouse or conduit piston instead of a rod. This tool is a small foam cylinder that is slightly smaller in diameter than the interior of the conduit.

It is used in tandem with a shop vacuum. The method for using this tool is detailed below:. This method is very useful for conduit with more complex twists and turns but can be limited by the length of the conduit. The fishing weight method uses a heavy fishing weight to guide wiring directly through a conduit. This method is somewhat limited in its applicability. It works best for straight, vertically-run conduit, though it can be applied to almost any conduit that is free to move around.

It is not ideal for a conduit that is fixed in a horizontal position or has excessive curves. The above methods are excellent for straight conduits but are much more difficult for pulling through conduits with more curvature. So how do you pull wire through flexible conduit with multiple turns? The fish tape method is the most common solution. This technique uses fish tape, a tool commonly used by electricians for pulling wire. Fish tape is a long, flat metal wire wound inside a spool with a hook at the end.

The fish tape method works as follows:. The fish tape method can be applied to nearly all types of conduit. Note that fish tape is available in a range of lengths from 25 feet to feet, so be sure to get one appropriate for your application. For shorter lengths or small jobs, nylon tape is an economical option that works just as well.

In some cases you may encounter conduit with 90 degree turns or existing wires — both of these can prove problematic.

Pulling wire through conduit with existing wires is difficult because any technique you use may get caught on the existing wires — the conduit mouse and fishing weight method are completely unuseable in these cases for this reason. Pulling cable through conduit bends can also prove problematic. For most conduit, the more severe the angle, the more difficult it is to get a pull string or fish tape in place.

This problem is even more pronounced with PVC conduit, as the angle joints can easily catch fish tape as it works through the conduit. One method to get around these problems uses two fish tapes run at each end of the conduit. Note that this method does require working with a partner. The method goes as follows:. Before you pick one of the above techniques for pulling wire through conduit, it is important to analyze your conditions and adequately prepare for the process. Some essential tips include the following:.

The thickness of the conduit, as well as the texture, will help determine the best method for pulling wire through the conduit.