Can I cut a heating element shorter or extend a heating element by splicing two together?

The quick answer is no. But let us explain why.

The heating element inside each individual mat and cable is designed to produce a set amount of heat: 12–15 watts/sq ft or 41–51 BTUs (the measure of energy). Shortening the length of a heating element will cause it to produce more than the set amount of heat. Doing so can:

  • Decrease the life-span of the system
  • Void the warranty
  • Cause the system to fail compliance (based on the North American electrical code)

We’ll review the basics of electricity to help explain why a heating element can’t be shortened.

Basic units of electricity:

  • Voltage (V)
    • Measured in volts and identifies electrical power
  • Current (I)
    • Measured in amps
  • Resistance (R)
    • Measured in ohms (Ω)
  • Power (P)
    • Measured in watts

To better understand these terms, think of plumbing pipes. The voltage (V) is equivalent to water pressure, the current (I) is equivalent to the flow rate of the water, and the resistance (R or Ω) is like the pipe size.

Another way to think of this is to imagine pointing a water hose at a waterwheel. You can increase the power (P or watts) generated by the waterwheel in two ways.

  • If you increase the pressure of the water coming out of the hose (V or volts), it hits the waterwheel with a lot more force and the wheel turns faster, generating more power.
  • If you increase the flow rate (current or amps), the waterwheel turns faster because of the weight of the extra water hitting it.

How does this relate to electric radiant floor heating? Electric radiant floor heating systems use “resistant heating” elements. The key to understanding this is knowing each mat and cable is made with a specific resistance or number of ohms.

At the beginning of this article we stated that each mat and cable is designed to produce 12–15 watts/sq ft or 41–51 BTUs. Applying the basics of electricity, we know that the specific amount of heat means we have a required amount of resistance. Producing the correct amount of heat for your floor depends on the amount of resistance and voltage working together. By shortening or extending the heating element, you are changing the amount of resistance.

Heating a floor is different from the heating of air because the floor absorbs and holds the heat in place, while air being heated in a room moves and spreads.

Remember: Hot air (not heat!) rises, but your floor stays in one place as it heats up and creates a thermal mass (think of a hot pan on a stovetop).

If the resistance of the heating elements in your floor could be dialed up or down like the ones in a space heater or an electric stove, it could become too hot or heat up too quickly.

Our manufacturers create each mat and cable with a specific resistance to ensure your heated floor will be comfortable, efficient and above all safe. Shortening or lengthening the heating elements will compromise the carefully built and tested designs.

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