Whether for new construction or renovation, contractors and consumers will appreciate the ease of installation of electric mat-style floor warming. Other types of systems force contractors to install gauges or anchoring devices to the sub floor at uniform intervals, then manually feed the cable into position and secure it with glue, staples or clips.
Mat systems, however, take less time to install as many are pre-terminated and adhere directly to the floor. They also offer uniform cable spacing, saving the installer time and effort while eliminating the risk of spacing errors that can lead to cable burn out or cold spots in the floor. Furthermore, mat systems can be conformed to easily accommodate the dimensions of any room. The remainder of this article will provide a basic overview of how to install a mat system under a tile or natural stone floor.
Electric Floor Warming Mat System InstallationTo select the appropriate size system, make sure the floor-warming mat is no larger than the area to be heated. The floor area to be heated should not include permanent fixtures such as vanities, cabinets, toilets, showers, sinks or tubs. Generally, floor-warming mats come in various sizes to cover up to 200 square feet. For areas larger than 100 square feet, select a 240-volt version with an extension kit.
Step one of any installation involves measuring the area to be warmed. Take a typical bathroom. It may measure 96 square feet, for example, but when you subtract the area occupied by the vanity, shower and toilet, the total heated area is reduced to, say 74 square feet. In this case, you specify the 70-square-foot mat.
Step two is to determine the correct supply voltage (120 volt or 240 volt. The voltage is determined by either what is available in the area, or by the size of the area to be heated. The maximum area that can be heated by a 120-volt supply is 100 square feet. If the area is larger use a 240-volt supply, or dedicate two 120-volt circuits with separate floor warming systems. Each circuit must be on a dedicated circuit breaker. Nuisance tripping can occur if outlets are shared with the floor warming system. Plugging in a hair dryer with the floor warming system will draw more amps than one circuit breaker can typically handle and it will trip leaving a cold floor until the homeowner discovers it.
The thermostat should be rough wired to the electrical supply at this point. Fish the heating mat cold lead and floor sensor cable to the thermostat as the mat is positioned, before any mortar is applied.
Now the actual product installation begins. Layout the mat so that the area to be heated is completely covered(Figure 3A). Start near the thermostat where the ten-foot cold lead is within reach. The mat is easily rolled out over the sub-floor with the adhesive backing securing it in place until the leveling coat is applied(Figure 3B). The direction the mat is rolled out can be simply changed by trimming the fiberglass mesh, reorient the mat and then continue to unroll it(Figure 3C).
After the mat has been positioned over the area to be heated, the floor sensor must be installed. The sensor bulb should be placed between runs of heating cable and away from the edge of the heated area.
At this point the floor is covered with the un-rolled mat and the floor sensor is installed. Inspect the installation and make sure the power connection, end termination and the floor sensor do not protrude above the heating cable. If they are higher, gouge out some flooring material so they lay flat. Some unevenness in the heating cable can be overcome while installing the leveling coat but taking time to ensure the installation is flat and even will make the subsequent jobs much easier.
It is common practice to test the system at this point to ensure that no damage to the system has occurred before mortar is applied. The installation instructions included detail how to verify the heating cable and sensor are intact and functional.
Once the system is installed and confirmed functional it should be covered in a leveling coat of latex modified thin-set or self-leveling underlayment. The mortar is applied at a thickness that will just cover the mat, cable terminations and floor sensor. Be sure to apply the leveling coat to the entire floor providing an even surface for the final tile or natural stone flooring. Follow the manufacturer’s instructions and allow the leveling coat to fully cure before installing the final floor covering.
Install the tile or stone in accordance with the manufacturers instructions. Your floor warming installation is complete and can be put into service when the installation has cured sufficiently. Consult the thin-set and grout manufacturers’ installation instructions.
To start-up the floor warming system, connect the floor warming mat cold lead and floor sensor wires to the thermostat, being sure to connect the braid wire to the electrical ground. Turn on the voltage to the thermostat and program it by following the instructions provided. The thermostat will require that you input the time and day of the week so the clock function can operate your floor warming system when and how you desire it.