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Slab Heating Mat 120V, 3′ x 25′, 75 sq.ft., 12.5A

Slab Heating Mat 120V, 3′ x 25′, 75 sq.ft., 12.5A

Part Number: WSHM-120-03025
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Quebec Repairability Notice
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Notices

Quebec Repairability Notice

Avis important pour les consommateurs du Québec:

WarmlyYours n’offre pas de services de réparation pour ce produit. Les seules pièces de rechange disponibles sont les kits de raccordement (splice kits) ; l’élément chauffant lui-même n’est pas offert comme pièce de rechange. Si votre système de chauffage par le sol intérieur tombe en panne pendant la période de garantie, nous remplacerons l’unité complète conformément à notre politique de garantie. Notre équipe d’assistance technique est disponible 24h/24 et 7j/7 par téléphone pour toute aide à l’installation ou au dépannage. Pour plus de détails, consultez notre politique de retour. Cet avis est fourni conformément à la Loi sur la protection du consommateur du Québec, article 39 (telle qu’amendée en 2025).

Important Notice for Québec Consumers:

WarmlyYours does not provide repair services for this product. The only replacement parts available are splice kits; the heating element itself is not available as a replacement part. If your indoor floor heating system fails within the warranty period, we will replace the entire unit according to our warranty policy. Our technical support team is available 24/7 by phone for installation and troubleshooting assistance. For full details, see our Return Policy. This notice is provided in accordance with Québec’s Consumer Protection Act, section 39 (as amended in 2025).

Support Questions

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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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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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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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WarmlyYours has recently begun including floor sensors with our heating elements to help ensure customers will have everything they need for optimal operation of their radiant heating systems.

The sensor included with your floor heating element can be installed with the heating system (the sensor is equally spaced between runs of the heating wire--see your install manual for more info). Installing this sensor with your floor heating control will enable energy efficient operation of the floor warming system based on the floor temperature instead of the ambient room temperature.

We generally recommend that you install a second, unconnected backup floor sensor alongside the primary one. In the very unlikely event that your first floor sensor is damaged, this install method will save you from having to pry up flooring to replace a floor sensor. You simply disconnect the damaged sensor from the thermostat and connect the backup sensor.

In addition to the floor sensor that was included with your heating element, our nSpiration Series thermostats also come with a floor sensor. If you purchase both a heating element and an nSpiration Series thermostat from WarmlyYours, you'll have a primary and a backup floor sensor for your system.

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

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Resistance greater than this value may result in overheating or even total failure of the floor heating system. This may be caused by a crimping or other damage to the wire.

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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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A digital meter with a 0-200 Ohms scale ( Ω ) to measure the heating wire's resistance, and a 20K scale to measure the sensor's resistance.

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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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Turn the power (circuit breaker typically) to the thermostat off for 5 minutes and then back on to reset the thermostat.

If there is power to the thermostat and it still doesn't appear to work, then the next step toward a solution is to take Ohm measurements of the floor heating system.

This is done with a digital multi-meter that can select a low 200 Ohm (Ω) scale. To conduct this test, turn off the circuit breaker. Remove the thermostat completely from the wall and disconnect the wires connected to the LOAD connections at the back of the thermostat. Disconnect the ground wires from the house ground, and do the test shown on the links below. If you are uncomfortable doing this test, contact a qualified electrician.

Please follow one of these guides based on the type of heating system installed:

TempZone Single Conductor

TempZone Twin Conductor

For a quick overview of the testing process:

Here is a video showing how the test is done

Here is a video showing how to locate and identify the floor heating wires

If the system still does not function, contact +1 (800) 875-5285 WarmlyYours Technical Support and provide the Ohm measurements for further assistance.

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Single Conductor vs. Twin Conductor Identification

  • A single conductor floor heating system is a loop of one core wire, it starts at the thermostat and ends at the thermostat - this is the original method of manufacturing heating cable. Most single conductor floor heating systems have the same color cold lead wire connected to both load terminals/pigtails of the thermostat. Some early single conductor floor heating systems were produced with a white and a yellow cold lead wire.
  • A twin conductor floor heating system terminates two core wires at the end, both wires start at the thermostat - this is the current method of manufacturing heating cable. Most twin conductor floor heating systems will have two different colored cold lead wires, and one of these is black. The other wire in a WarmlyYours floor heating system is either yellow (120V system) or red (240V system).  A few early Environ systems had two black cold lead wires.

Note:

- Not all heating cables are wired directly to the thermostat. It may have been necessary during installation to terminate the heating cable in a junction box, and then run a separate (contractor-supplied) wire from the junction box to the thermostat.

- WarmlyYours single conductor cold leads were produced with a 13‘ length at the start of the loop, and a 26‘ length at the end.  The 120V floor heating systems had a yellow and a white label attached to the cold leads, and the 240V floor heating systems had a red and a white label attached. 

- If you have a single conductor floor heating system and notice that one cold lead is thicker or feels hotter than the other, please contact technical support at +1 (800) 875-5285 

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Test the Slab Heating cable or mat using a digital ohm meter as shown here. Also test the slab heating cable or mat using a Mega Ohm meter as shown here. And this video shows how to do the Ohm test.

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A variance of +/- 15% is acceptable.

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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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Resistance below this value may result in no heating or cold spots in the floor. This may be caused by exposure to moisture or other conductive material that penetrates the core insulation.

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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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For systems below 12 Amps, a 15 Amp, Non-GFI breaker is fine. For systems 12 to 16 Amps, a 20 Amp, non-GFI breaker is needed. Breaker sizes are noted on the installation plan that ships with many orders.

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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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Temperature affects core resistance - lower temperatures decrease resistance and higher temperatures increase resistance. Another consideration is the test equipment, sometimes switching test units, adjusting the calibration, or allowing for the verified differential may be necessary.

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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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Specifications

Electrical

Amps 12.5 A
Floor Load 1.5 kW
Ohms 9.6 Ω
Thermal Power 1.5 kW
Voltage 120 V
Watts 1500 W
Watts Per Sq. Ft. 20 Watts Per Sq. Ft.

Warranty / Certifications

Approvals cCSAus Listed
Warranty 10 Year Warranty

Performance

BTU Per Hour 5118 Btu

Product Dimensions

Cold Lead Length 20′
Coverage 75 ft²
Heating Element Thickness ¼″
Length 25′
Size 3′ x 25′
Weight 14.7 lbs
Width 3′

Installation

Floor Types Installs in concrete

Identifiers

SKU WSHM-120-03025
UPC (GTIN-12) 881308020811

Logistics

UNSPSC Code 40101830

Cabling Specs

Wire Energy efficient twin-conductor

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