TempZone™ Floor Heating Ruler Cable 120V, (3.7W/ft.), 300 ft., 9.3A

Part Number: RCT-120-0300
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Common Support Questions (4)

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Common Support Questions

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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When WarmlyYours electric floor heating systems are being installed on a concrete slab, we strongly recommend adding a layer of insulation over the slab prior to installing the system. While our electric floor heating provides up to 25% more heating power per square foot than many of our competitors, the slab will always act as a "heat sink." Some of the heat that would otherwise be transferred to the flooring surface will remain in the slab, causing the floor’s surface temperature to be considerably lower. This is true with any electric radiant floor heating system.

When installed on top of a concrete slab without insulation, it is generally accepted that electric floor heating will take the chill away from the floor and provide a small amount of warmth. Adding insulation on top of the slab and beneath any electric radiant floor heating system will allow a greater percentage of the heat generated to transfer to the flooring surface. This results in greater efficiency and therefore faster warm up times, higher expected surface temperatures and lower energy usage. The floor will have the capacity to warm to a comfortable temperature, and in some cases can be employed as the primary heat source for that room.

The recommended types of insulation are natural cork, insulated tile backer boards and insulated underlayment, such as ThermalSheet™ synthetic cork.

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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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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.


- 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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Publications and Manuals



Amps 9.25 A
Cold Lead AWG 18
Floor Load 1.11 kW
Ohms 12.97 Ω
Ohms Per Ft 0.043 Ohm/ft
Thermal Power 1.11 kW
Voltage 120 V
Watts 1110 W
Watts Per Sq. Ft at 3.75 Inch Spacing Up to 12
Watts Per Sq. Ft. 9-15
Watts Per Sq. Ft. at 3 Inch Spacing Up to 15
Watts Per Sq. Ft. at 4 Inch Spacing Up to 11
Watts Per Sq. Ft. at 5 Inch Spacing Up to 9

Warranty / Certifications

Approvals cULus
Warranty 25 Year Warranty
Wet Location Listed US, Canada


BTU Per Hour 3787 Btu


Country of Origin (COO) India

Product Dimensions

Coverage at 3 Inch Spacing 75 ft²
Coverage at 3.5 Inch Spacing 87.5 ft²
Coverage at 3.75 Inch Spacing 93.8 ft²
Coverage at 4 Inch Spacing 100 ft²
Coverage at 5 Inch Spacing 125 ft²
Heating Element Thickness 0.1875″ / 4.318mm
Length 300′


Floor Types Tile, Marble, Stone, Vinyl, LVT, LVP
Ideal Cable Spacing with Fixing Strips 4″
Ideal Cable Spacing with Prodeso Membrane 3.75″


SKU RCT-120-0300
UPC (GTIN-12) 881308076252



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