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Slab Heat Cables Frequently Asked Questions

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Frequently Asked Questions

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While WarmlyYours electric radiant floor heating systems are typically installed by your floor covering contractor, a licensed electrician is recommended for the final thermostat hook-up. With every quote, we provide an Installation Plan layout, together with an electrical plan that has all the info required for the electrician.

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Our electric radiant floor heating systems have withstood rigorous safety testing and earned the UL listing. They produce much less EMF than common household appliances like your TV or vacuum cleaner. The EPRI (Electric Power Research Institute) tests all electrical devices and publishes the data. Many common household appliances are tested at a distance of 6 inches. The test results indicate that on average, the EMF emitted for the following appliances, measured in Milligauss (mG) units, is:

Vacuum Cleaner: 300 mG

Microwave: 200 mG

Portable Heater: 100 mG

Dishwasher: 20 mG

Washing Machine: 20 mG

WarmlyYours TempZone™ (Twin): 1.8 mG

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The floor heating systems are offered in both 120 volt and 240 volt for the North American market. A 208 volt breaker panel can also accommodate our 240 volt floor heating system. It is important to note that the energy consumption will be the same: a 240 volt system will not cost more to operate than a 120 volt system. You are billed in kilowatts, and the 120 volt and 240 volt systems use the same amount of kilowatts. WarmlyYours often specifies a 120 volt system in smaller projects while a 240 volt system is typically recommended for larger projects (120 square feet of electric floor heating coverage or more). The benefit of switching to a 240 volt system is the reduction in amperage. Our programmable thermostat can control a radiant floor system up to 15 amps. The 120 volt system will reach 15 amps at 120 square feet of electric floor heating coverage. However, the 240 volt system will reach 15 amps at 240 square feet of electric floor heating coverage, allowing a much larger system to be connected to the thermostat. For installations over 240 square feet, a relay contactor or power modules are needed.

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Yes. Unlike the heating cable for electric floor heating, the cold lead wires can be trimmed.

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To prevent any melting, ensure that the heating wire is at least 4” from the toilet wax ring.

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Electric radiant floor heating should not be installed under permanent fixtures that may trap heat. However, if the vanity or cabinets are "floating" or are on legs, then a floor heating system may be installed under it.

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Please keep in mind that you must check your electric floor heating system with a digital ohmmeter in conjunction with a Circuit Check™. Take an initial reading as soon as you take the product out of the box to verify that it is within -5% / +10% of the values stated on the product’s label. This will give you a basis of comparison for future readings. Take a second reading once you have positioned the system to match your custom installation plan. It is also advisable to take an additional reading in the middle of the tile installation, just to make sure that the Circuit Check™ is doing its job. Then, take a final reading when you are finished with the floor installation and are ready to hook up the thermostat.

The Circuit Check™ is a tool developed by WarmlyYours to give you peace of mind and ensure trouble-free installations. Simply hook up the cold leads to the tool while you position the system to match your custom installation plan.

The Circuit Check™ will continuously monitor the continuity of the circuit during the installation of your system and during the installation of your flooring. The Circuit Check™ beeps immediately when a short in the system is detected, alerting you to a potentially damaged cable in the area you are working, before you lay the tile over the electric floor heating system.
 The WarmlyYours technical support team is available 24/7 to provide assistance if the alarm sounds, or if you would have any questions during your installation.

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When installing electric floor heating over a concrete slab, an insulating underlayment like ThermalSheet is highly recommended to ensure efficient operation, faster heating times and warmer floor temperatures.

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Yes, but any furniture that may trap heat, such as pieces with an enclosed bottom, should be avoided. Furniture on legs with a clearance of at least 3" is permissible.

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Electric-resistance heating cables and systems have no polarity. This includes all current WarmlyYours heating elements.

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The amount of amperage draw depends upon how large the area is that you are heating. For coverage of areas less than 30 square feet, a 120V Slab Heat system will draw less than 6 amps. If you have a larger area over 180 square feet of heated space, then you will need a larger breaker plus additional controls. No matter what the size of the area you choose to heat, we recommend a dedicated circuit for your electric radiant floor heating system.

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Yes. While there are some floor heating systems that can be installed beneath floor joists, most electric radiant floor heating systems will need to be installed beneath the floor itself. This is why the best time to install electric floor heating is during a remodel or as a part of a new construction, when a floor is being installed anyways. 

If you’re interested in alternative radiant heating methods, check out our Infrared Heating Panels, which are wall-mounted and use infrared technology to provide supplemental heating. 

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The breaker and wire sizes are selected based on the total amperage of the WarmlyYours heating system connected to a single thermostat. This information is on the WarmlyYours heating system's installation plan, electrical plan, or UL label. Based on guidelines from the National Electrical Code: loads up to 16 Amps may utilize 12 gauge wire with a 20-Amp breaker, and loads up to 12 Amps - 14 gauge wire with a 15-Amp breaker. Local code and/or other factors may change these guidelines.

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One thermostat can control multiple heating mats/cables as long as all the heating elements are using less than 15 amps:

TempZone™ will cover aprx. 120 sq. ft. for 120V systems and 240 sq. ft. for 240V systems on one thermostat.

Environ™ will cover aprx. 150 sq. ft. for 120V systems and 300 sq. ft. for 240V systems on one thermostat.

Slab Heat will cover aprx. 90 sq. ft. for 120V systems and 180 sq. ft. for 240V systems on one thermostat.

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The ground wire in the floor mat must be connected directly to the ground wire of the supply or to the house ground wire.

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The requirements are determined as follows: plan on 20 watts per square foot (at 3" spacing) without a floor covering; or 15 watts per square foot (at 5" spacing, cable only) with a floor covering. To calculate approximate power requirements, multiply the square feet by either 20 or 15 (per the above), and then divide by the voltage (120V or 240V) to arrive at Amps.

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The cost for the heating elements in a Slab Heating system is $7 per sq. ft. ($8 CAD) for Slab Heating Mats and $7 per sq. ft. ($9 CAD) for Slab Heating Cables.

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The Slab Heat radiant system adds no additional height. This is because it is embedded within the concrete pour.

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You can control your slab heating system with any WarmlyYours nSpiration Series thermostat. Depending on the size of your project, you may also need to add a relay or nJoin power module.

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Stop installation, box out a 3"×3" area surrounding the damaged area, and call tech support at (800) 875-5285.

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Any trade professional is qualified to layout slab heating cables and/or mats; electricians must make the electrical connections and test the wire; you can hire a concrete contractor to install the concrete for you.

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Never cut, shorten or splice the heating cable itself; cutting it damages the system. Only the non-heating cold lead can be shortened, as your product’s manual allows. Order the size your SmartPlan™ specifies, because unused cable can’t be cut off.

Some mats let you cut the mesh, never the cable, to turn or reposition them: TempZone™ and Environ™ Flex Rolls and Slab Heat mats. TempZone™ Easy Mats and Custom Mats are made to size and must not be shortened or cut. TempZone™ Cable has no mesh: lay all of it at the spacing on your SmartPlan™.

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Many homeowners choose to lay the heating mats or cables themselves as a DIY project while they are putting down new flooring. However, we always recommend that a licensed electrician perform the final hookup to the thermostat and power source to ensure everything is up to code.

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It depends on the floor. Tile and other bonded floors shouldn’t go over a loose plastic sheet: bond ThermalSheet to a cured, dry slab with modified thinset; a waterproof concrete sealer may be needed if slab moisture is above 10%. Under floating laminate or engineered wood, a plastic vapor barrier beneath the underlayment is fine. Fix any water seepage first.

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Installing electric radiant heating in a concrete slab is done during the construction or renovation process, before the concrete is poured. Here is a step-by-step overview:

  1. Prepare the subbase: Ensure the ground is properly compacted and a vapor barrier is in place. Add rigid foam insulation beneath the slab to prevent heat loss downward into the ground — this is critical for efficiency.
  2. Lay rebar or wire mesh: The heating cable will be tied to this grid to hold it in position during the pour.
  3. Install the heating cable: WarmlyYours electric heating cable is laid out in parallel runs at a consistent spacing (typically 3–4 inches apart for primary heat, wider for supplemental). Never cross or overlap cables.
  4. Connect the cold leads: The non-heating lead wires are routed to the wall where the thermostat will be mounted.
  5. Test the cable resistance: Before pouring, verify the cable resistance with a multimeter to confirm no damage has occurred. Record the reading.
  6. Pour the concrete: The slab is poured carefully over the cables. Avoid dragging equipment directly over the cables.
  7. Install the thermostat: Once the slab has cured (typically 28 days), connect the system to a WarmlyYours thermostat and commission the system.

Get a Custom Installation Plan

WarmlyYours provides a free SmartPlan™ — a professional layout drawn by our engineers showing exact cable placement, spacing, and wattage for your specific slab. You can also get an Instant Quote online in minutes.

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Operating costs for electric floor heating depend on the heated area, system wattage, your local electricity rate, and how long the system runs: (area × watts per sq. ft. ÷ 1,000) × electricity rate × hours energized.

For example, heating a 35 sq. ft. bathroom with a 15-watt-per-square-foot system draws 525 watts (35 × 15 ÷ 1,000 = 0.525 kW). Running the system for 8 hours a day costs approximately $0.68/day ($20.49/month).

You can calculate specific operating costs for your project using our

Operating Cost Calculator for Floor Heating

Estimate your daily and monthly energy costs based on room size and local rates.
sq. ft.
¢/kWh
Estimated Cost
$0.04
per hour
$0.15
per day
$4.50
per month
Rae Radiant

"Most homeowners are surprised how affordable radiant floor heating is to operate—often just pennies a day for a bathroom. It's the kind of everyday luxury that pays for itself in comfort!"

— Rae Radiant
.

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For the same wattage and operating time, 120V and 240V electric floor heating use the same amount of energy and produce the same heat. A 240V system draws less current for the same wattage, which can accommodate a larger heated area on a suitable circuit. Choose the heating product and control voltage to match the supply, and have an electrician verify circuit capacity, wiring, and applicable code.

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Most floor coverings work well over heated concrete slabs, including tile, stone, luxury vinyl tile (LVT), laminate, and engineered wood. Tile and stone are the most efficient as they conduct heat naturally. Always check with the flooring manufacturer to ensure their specific product is rated for use with radiant heat.

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In-slab radiant heating involves embedding heating cables, like WarmlyYours Slab Heating cables, directly into a new concrete pour (usually 2-4 inches thick). This turns the entire slab into a thermal mass that radiates consistent, long-lasting heat, making it ideal for basements, garages, and home additions.

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The layers for the full installation are as follows:

  • Bottom: 8-12” of compressed crushed rock aggregate (may already exist)
  • 2” polystyrene insulation
  • 2-3” layer of concrete
  • Rebar and/or reinforcing mesh and attach the cable or mat
  • Top: Pour a 2-3” layer of concrete as the final flooring surface

Call tech support at +1 (800) 875-5285 to customize this to your unique application.

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WarmlyYours floor heating systems are backed by our industry-leading warranties, among the longest in the radiant heating industry:

Product Warranties:

  • TempZone™ systems – 25-year product warranty on heating cables and mats
  • Environ™ systems – 25-year product warranty on heating cables and mats
  • Thermostats – 3-year manufacturer warranty on all models
  • Installation materials – Covered under respective product warranties

What's Covered:

  • Manufacturing defects in heating cables, mats, and components
  • Free replacement of defective products during warranty period
  • Technical support for troubleshooting and diagnostics
  • Installation guidance to prevent issues before they occur

Why Our Warranty Matters:

  • Proven reliability – Over 25 years of manufacturing experience
  • Rigorous testing – Every system tested before shipping
  • Quality materials – Premium components designed for decades of service
  • Installation support – 24/7 tech support during installation to prevent warranty issues
  • Peace of mind – Your investment is protected for decades

Warranty Registration:

Your SmartPlan™ includes warranty documentation and testing logs. We recommend:

  • Testing resistance before, during, and after installation
  • Documenting all resistance readings
  • Taking photos of your installation
  • Registering your system online after installation

Beyond the Warranty:

Even after your warranty period, our support team remains available to help with:

  • Troubleshooting and diagnostics
  • System expansions to additional rooms
  • Replacement thermostats and accessories
  • Technical guidance for any issues

Your SmartPlan™ ensures your system is properly designed and installed from day one, minimizing the chance of issues and maximizing the life of your investment.

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You should install the cable 2-3" below the finished surface, and attach it to rebar and/or reinforcing wire mesh to secure the cable in place.

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A floor sensor measures floor temperature so a compatible thermostat can regulate comfort and enforce the flooring manufacturer’s temperature limit. Some thermostats, including nTrust 2.0, offer a regulator mode without a sensor, but that mode does not measure floor temperature. Use sensor-based temperature control whenever required by the flooring or heating-system instructions.

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