Construction Notes – This information is based on the INFLOOR WFK 120-volt electric system, primarily designed for use in floors. Don't use the heating cable for any other type of application without first contacting the manufacturer for advice. Maxxon offers WFKs in three sizes, each designed to cover a specific range of floor area. Don't alter the length of any heating cable to make it fit a floor area larger or smaller than the recommended range for that cable. Also, the heating cable must not touch, cross, or overlap itself at any point. This could cause the cable to overheat, possibly requiring cable replacement.

To create a warmer floor, especially over a crawl space, insulate the floor joists and install a vapor barrier. This will reduce energy consumption and improve overall system performance. You should contact the manufacturer for complete instructions on how to install it, but keep the following in mind:

1. Select an appropriate location for the 4-inch square electrical outlet (metal) box. Install the box 60 inches off the floor on an interior wall.

2. Below the outlet box, drill ³/₄-inch holes halfway into the side of the bottom plate. Then drill one hole in the top of the plate to accommodate the bending radius of the cable and two holes for the thermostat. On the thermostat hole, be sure to chisel off the points in the drilled hole.

3. Remove knockouts in the outlet box and install bushings. Before hanging wallboard, insert pull-cords through the knockouts and the holes previously drilled in the plate. Leave the cords long enough to tie to the cables and thermostat tube. This cord lets you pull the components up into the outlet box after the wall has been finished (Figure 7-11). Don't forget to tie off the cord in the outlet. You don't want the cord to fall through the hole after the wallboard is hung!

Photo Courtesy of: Maxxon Corporation

Figure 7-11: Insert pull-cords for the cable and tube

4. Mark off the perimeter of the area to be heated (maintaining a 6-inch border between walls, cabinets and fixtures and the heated area). Unwind the cable to expose the "cold" lead so you can tie it to the cord and pull it up into the outlet box. Pull the wire so the splice can be located within 12 inches of the guard plate. The factory splice between the "cold" lead and the heating cable must be located on the subfloor.

5. Before running the first length of cable along the border to the opposite side of the room, install a plastic clip on the cable as it exits the hole in the plate. When you're installing it directly on concrete, you can glue or nail the clips to the concrete.

6. Now, on the opposite side of the room, fill in the area with cable, working your way back to the original side of the room. Maintain a uniform 4- or 6-inch spacing. Either mark the floor or use a template as shown in Figure 7-14 A. Once you've installed the plastic clips, weave the heating cable under the clips (Figure 7-14 B).

Figure 7-14 A (below) and Figure 7-14 B (right) Installing the cables Photo Courtesy of: Maxxon Corporation

Photo Courtesy of: Maxxon Corporation

7. When you reach your starting point (in front of the outlet box), tie the end with the second "cold" lead and pull the wire up into the outlet box, again keeping the factory spline on the floor.

8. Install the thermostat tube after the wire (or wires). It's important to place the tube between two heating cables.

9. Before pouring any underlayment, check the continuity of the cable to make sure it wasn't damaged during installation. The resistance of the cable should be less than 150 ohms. Do not energize the heating cable to see that it works.

10. Cover the cables with ³/₄ inch of thermal mass, mortar, or Therma-Floor.

11. Now install your tile and connect the wires to the thermostat.

Previous | Next

Table of Contents | Chapter Seven | Find a Bookstore