Installing Floor Warming Systems

Ceramic and stone tile make beautiful floor covering and are favored choices for rooms such as bathrooms and kitchens. One significant drawback, however, is how cold it can be to walk on in bare feet. This is especially true during cold season months.

One remedy for this problem is the installation of a floor-warming system underneath the tiles. Something enjoyed by some 850,000 households across the United States and Canada. Characteristically, these systems consist of one or more thin mats with electric resistance wires, and are installed in thin set cement. Normally, they are hard-wired to a 120-volt GFCI circuit, and controlled using a timer-thermostat; much like an electric blanket.

Besides providing an evenly warm walking surface, floor warming systems offer a secondary heat source that increases room temperature comfort level; allowing you to zone heat your home and reduce heating bills. Another great thing about floor-warming systems is how cost-effective they are. Because heat isn’t forced through ducts or lost rising to the ceiling, most systems operate on less than 10-cents a day!

Households with Energy Star rated, programmable thermostat floor-heating systems in their bathrooms, kitchens, basements, or other rooms of the house can reduce energy costs by as much as 40-percent.

Because the system functions with a sensor in the floor and does not measure air temperature of the room, the thermostat can be placed in a closet or another unseen, inconspicuous location. Although installation of the mats and cold lead wire work can be accomplished by a do-it-yourselfer, timer and thermostat connection are aspects that should be handled by an experienced electrician.

Safe, quiet, relatively easy to install, and a great way to provide more consistent temperatures throughout the house and get rid of “discomfort zones,” there are floor-warming system mats that can also be installed under vinyl, laminate, and engineered wood floors. If not being installed directly over cement, install cementboard as a subfloor before laying the mats.

Systems normally range from $300 to $600 for the average sized-bathroom of around 30 square feet. There are various sized mats for larger rooms; custom made systems are also available.

What to look for in a Floor-warming System

• Select a floor-warming system that can be installed in a single layer of thin set cement rather than two layers. This allows for faster, easier installation a DIY handyman can more easily handle.
• Look for cold lead wires long enough to connect to the thermostat without requiring cut-&-turns of the mat to bring it closer to the thermostat.
• Some products weave the wires over and under a fiberglass net – leaving some areas of the wire vulnerable to damage. Look for a product with a fiberglass net or other supporting material that completely covers the resistance wire. This helps ensure wires will not become nicked or damaged by the trowel during installation, when applying the adhesive.
• Look for a system with ultra-thin 1/8-inch thick cold-lead wires. Cold-lead wires as thin as the heat resistance wires will help ensure easy, complete coverage by the adhesive. Note: a system with thicker cold-lead wires will add extra steps to the installation process. It will require that either a groove be chiseled in the cement slab underneath, or cut in the plywood sub-floor or backer board to keep the floor level flat.

One cost-effective option to consider in place of a thermostat is a dimmer switch, which runs just under $40. Although the system would not turn on automatically, you would still be able to increase and decrease floor temperature manually.

Manual thermostats with floor sensors are available for under $70; programmable thermostats with sensors run around $150.

Although using a timer independent of a thermostat to heat the floor during certain periods is possible, it is not recommended. This is because the floor temperature will continue to increase as long as the timer is on – since the timer by itself has no floor sensor.

Finally, select a manufacturer that offers vender technical support that helps DIY homeowners by designing a layout for the system, customized to the homeowner’s own floor plan for maximized uniform heating.

Before and After Installation Checks

One critical aspect of installing a floor-warming system is to perform a resistance test to ensure heating wires were not damaged during shipping. Other tests should also be performed once the system is in place to ensure wires were not damaged during the installation process.

To check for wire damage prior to installation, inspect the resistance value of each heating mat using a digital multi-tester. Check the reading against the factory-tested reading noted in the manufacturer’s guide. Your reading should fall within the acceptable range determined in the guide. Otherwise, the mat has been damaged and should not be installed. Record the reading to compare against others that will be taken.

During installation, check the resistance of the mats periodically; once installation is complete, check the resistance once again.

How to Install a Floor-warming System under a Tile Floor
While keeping to the specific guidelines for whatever floor-warming system you are installing, pay attention to the basic steps below. In the event of a discrepancy between the two, always follow the manufacturer directions.

1. Remove the wall surface to expose the framing for installation of the boxes for the warmer system thermostat and timer. Install a 2 ½-inch deep by 4-inch wide double-gang box for the thermostat on one side of a stud; a single-gang electrical box for the timer on the other side. Note: select an easy-to-access location; box placement should be about 60-inches from the floor.
2. Make holes for routing the power leads and thermostat sensor wire. Use a plumb bob or level to mark points on the bottom wall plate directly below the two knockouts on the thermostat box. At each mark, drill a ½-inch hole down through the top of the plate; drill two more holes through the sides of the plate as close to the floor as possible, to intersect the top holes.
3. Using a tube cutter, cut two lengths of ½-inch thin wall electrical conduit to fit between the thermostat box and the bottom plate. If installing 3 or more mats, use ¾-inch conduit instead.
4. Place the bottom end of each conduit up about ¼-inch into a hole in the bottom plate. Using a setscrew fitting, fasten the top end to the thermostat box.
5. Run a 12-gauge Nm electrical cable from the service panel to the timer box; attach it using a cable clamp. Be sure and leave about 8-inches of extra cable extending from the box.
6. About 12-inchs above the boxes, drill a 5/8-inch hole through the center of the stud. Making a smooth curve, run a short branch cable from the timer box through the drilled hole, to the thermostat. Secure both ends using clamps.

After planning out ceramic or other tile and snap reference lines, vacuum the floor thoroughly and spread out the heating mats. Make sure the power leads are positioned closest to the electrical boxes.

Mats should be positioned no closer than 3-inches to walls, showers, tubs, toilet flanges, or other permanent fixtures in the room. They should be positioned 1 to 2-inches under the kick space of vanities to prevent hot heels and cold toes when standing in front of the vanity.

The mat, however, should not be positioned under the cabinet itself, or under expansion joints in the concrete slab. Individual mats should be set close together, but should not overlap; heating wires should be no closer than 2-inches from wires on neighboring mats.

Once the mats are in place, check to insure power leads will reach the thermostat box. The mats should be completely flat, wrinkle and ripple free. Secure the mats to the floor using double-sided tape. Space tape about every 2-feet and press firmly to insure the mat is firmly secured.

Because insulated power leads are on the thick side, you will most probably have to create recesses in the floor for the connection between the power leads and heating-mat wires. Use a grinder or chisel and hammer to make the recess. Once the connection has been fitted in the recess, secure it using a bead of hot glue.

1. Thread steel fish tape down the conduits. Use electrical tape to attach the ends of the power leads to the fish tape; pull the fish tape and leads up the conduit.
2. Disconnect the fish tape, and secure the leads to the box using insulated clamps. Leave about 8-inches extending from the clamps; cut any access leads using snips or pliers.
3. Feed the heat sensor wire through the other conduit, and then weave it into the mesh of the nearest mat. Extend it into the mat 6 to 12-inches, and secure it in between two resistance wires using dabs of hot glue.
4. Using the multi-tester, test the resistance wires once again to ensure they are still undamaged; record the reading for future reference.

You are now ready to install the tile flooring. Use thin-set mortar as an adhesive; spread it carefully over the floor and warming mats using a square-notched trowel. Every so often, use the multi-tester to check the resistance reading to ensure no damage has been done to the mats. Once tile installation is completed, check mat resistance once again.

If everything checks out, complete the floor-warming installation process as follows:

1. Attach the adapter cover to the thermostat box. Patch the wall opening with wallboard.
2. Following the manufacturer’s instructions, complete the wiring connections for the thermostat and timer. Attach the sensor wire to the thermostat setscrew connection. Apply the manufacturer’s wring labels to the thermostat box and service panel. Mount the thermostat and timer; complete the circuit connection at the service panel.

Once the flooring materials have fully cured, test the floor warming system one last time to ensure it functions properly.

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