The last snowstorm to blow through did a number on your roof heat cable, and now a section of it is damaged. What to do? Am I able to splice together electric heating tape just like any other wire? Do I need an electrician? Or a roof heating expert? Good questions, and the answer to all of them is, ‘It depends.’
While self-regulating cable splicing is a bit more complicated than that for regular wire, it’s by no means impossible if you’re fairly handy and you have the right tools. Thankfully, most of the things you’ll need are likely already in your toolbox. Those are a pair of ProRex crimping pliers, a multitool crimper and wire stripper, some needle nose pliers, a diagonal wire cutter, a razor utility knife, and a heat gun.
You can choose from several different self-regulating heat wire splicing kits, and they cost anywhere from $20-$30. The main things in the kit are usually a large heat shrink tube, a smaller ¾” x 3” heat shrink tube, a couple of pieces of mastic tape, two heat shrink butt connectors, and a copper or nickel ground crimp sleeve. Some kits also contain a heat shrink end seal, which you may need if the damage is toward the end of your cable. And, of course, don’t forget to purchase enough of the new heat cable to handle the repair. A little overestimation isn’t a bad thing here. You can fine tune the measurements to match the new cable to the exact length of the portion you’re removing later.
Ready? Let’s Go!
1. Uninstall and Remove the Damaged Cable
You’ll need to remove the cable from your roof first. Please don’t try to splice anything up on the housetop. Simply leave the cable clips in place, so all you have to do when you're finished is attach the heat wire back into the clips.
Once you’re on a solid surface (preferably indoors), use the diagonal wire cutter to cut the cable cleanly at each edge of the damaged portion. If there are multiple spots where the wire is corrupted, consider removing that entire section instead of trying to splice numerous areas together. Heat cable splicing has a few more steps than standard wire splicing, so expect it to take longer.
2. Shed the Outer Jacket
Thread the large heat shrink tube, followed by the smaller one, onto one side of the cut cable and slide them down and out of the way for now. Next, take your utility knife and carefully score the circumference of the outer jacket of the cable about six inches in from the cut end. Flex the cable back and forth, so the jacket separates at the score’s edge. Then slice down the middle of the wire, again just enough to cut through the jacket, and gently remove the layer. Repeat the process on the other cable.
3. Keep the Braid
There should be a metal braid under the cable jacket you just removed. Push it away from the cut end, so it bunches up into the cable. At this point, you can either use a screwdriver or your finger to pry a hole in the braid. Bend the cable underneath the braid like an elbow and pull it through the hole. You’ll be left with the braid under the cable. Don’t cut this off. Pull it straight like a wire and bend it to the side.
4. Remove Insulation
About ½” to 1” above the point where the braid disappears back under the jacketed cable, score the wire again and remove the next layer. This housing, which sits under the braid, is the insulation. Now you should have just a flat black piece of cable exposed, known as the matrix, where the two bus wires are encapsulated on each side.
5. Start Stripping (the Bus Wires, That Is)
This part is a little trickier, as you need to be careful not to damage the bus wires while you’re stripping them. Use the diagonal wire cutter to make a v-shaped notch in the matrix area between the wires. With your needle nose pliers, grab the end of one wire and twist it until it peels away from the matrix. When you have pulled away both bus wires, cut the remaining matrix housing off at the same point where you cut the insulation. Using the utility knife, carefully whittle away any leftover pieces of the housing stuck to the bus wires. Do the same for the bus wires on the other cable.
6. Heat Shrink, Tape, Repeat
Cut the bus wires, so they’re about half as long as the heat shrink butt connectors. Slide each butt connector on a bus wire and crimp that side with the ProRex tool. Then thread the bus wires from the opposite cable into the connectors until they touch and securely crimp the other side. Using your heat gun, shrink the connectors onto the bus wires.
Continue to keep the metal braid on both sides bent away from the area where the bus wires are connected. Take a pack of mastic tape and wrap it around one side of the cable, weaving in and around the bus wires to about the middle of the butt connector. Do the same on the other end. When you’re finished, the mastic tape should cover the entire bus wire connection.
Slide the smaller heat shrink tube up over the entire assembly, again being careful to keep the braid wires out of the way. Use the heat gun to shrink the cables together. Finally, it’s time to take the braids on each end, thread them through the metal connector, and crimp them together. Cut off any remaining braid that extends out past the connector. Now pull the large heat shrink tube over everything and secure it with the heat gun.
7. You’re Done … Almost
Before re-installing, it’s a good idea to plug in your newly-repaired heat trace cable and conduct what’s known as a megger test with a 500 VDC megger. You want to see a minimum reading of 20 Ohms for each circuit. That means your heat wire is powering up properly. Double-check the length of the wire for any other issues, and then re-install. If you start to doubt your abilities at any stage of this process, don’t hesitate to contact a licensed expert in heat tracing and freeze protection, like our sister company, Wasatch Heat Cable. They’re always happy to help, and they will get you back on track in no time.