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How to check the resistance readings of your electric floor heating system.


To ensure that your floor heating system will function properly, always test the resistance of your wires with a digital multimeter set to 200Ω before, during, and after installation. Continue reading for detailed steps on how to check the resistance of your electric floor heating system.


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What should the resistance of my heating cable be?

Warmup’s underfloor heating cables are constant wattage cables and should be tested on a 200Ω scale. Each heater model has its own unique resistance reading that can be found on the product tag and on the box. Resistance can also be found on the product’s specification sheet.

Warmup recommends that you remove the tag from the cold tail lead of your heating cable and tape it inside of your electrical panel for future reference.

 

When should I take the resistance of my heating cable?

Resistance should be taken before, during, and after the installation of the underfloor heating system. For each step, it is important that you record the heater model number, the core-to-core resistance readings, and the resistance readings of each leg to ground. These records will be used to register your product warranty.

Taking resistance readings before installation.

First, resistance readings should be taken as soon as the cable is taken out of the box. While it is incredibly rare for a cable to be defective out of the box, it will rule out the possibility of that being the issue if it is found that the resistance is incorrect later on.

If the resistance of your cable is incorrect immediately after taking it out of the box, contact Warmup to replace the cable.

Taking resistance readings during the installation.

While installing the system, continue to take resistance readings throughout. This will help ensure that the cable is being installed correctly with no damage.

Warmup recommends using our Dual Cable Tester during installation, which simultaneously takes resistance readings and will sound an alarm if it detects damage to the cable.

If at any point there is damage to the cable during the installation process and before the floor finish is installed, contact Warmup, as you may be eligible for our SafetyNet Guarantee.

Take resistance readings after the installation.

Finally, take and record the resistance readings of the floor heating cable once the installation has been fully completed before connecting the lead wires into the thermostat. This will confirm that the installation has been successful and there is no damage to the cable.

If the resistance is out of range after the installation has been completed, contact Warmup for further assistance.

Note: During the installation, be sure to properly embed the factory joint and factory endcap of the heating cable with thinset. If this is not done properly, the cable will show proper resistance readings now, but can become damaged over time.

 

How to take resistance readings of a floor heating cable.

First, set your multimeter to 200Ω. The following tests should be performed before connecting the heating system to a power source or only after disconnecting if already installed.

Core-to-core readings.

Connect the black wire and red (240V) or yellow (120V) wire from the heating cable to the multimeter. This is the “core-to-core” resistance reading. Compare the ohm number that appears on the display to the resistance on the cable’s tag, box, or stated in the installation manual.

A +/- 5% range in resistance is acceptable. For example, if the resistance for your heater is 22Ω, a reading between 20.9Ω and 23.1Ω would be acceptable.

Leg-to-ground readings.

Next, connect the black wire and the neutral/ground wire from the heating cable to the multimeter. This is the first leg-to-ground resistance reading. You want to see the number “1” or the infinity symbol, “∞.”

Then, remove the black wire and connect the red (240V) or yellow (120V) wire from the heating cable. This is the second leg-to-ground resistance reading. You will, again, want to see the number “1” or the infinity symbol, “∞.”

If your results deviate in any way from the results indicated above, call Warmup immediately at (888) 927-6333 for further instructions.

 

Conclusion and contact for further assistance.

Testing the resistance of your floor heating system wires is an essential step in ensuring the proper functionality and performance of your system. By following the outlined procedures and using a digital multimeter set to 200Ω, you can accurately measure the resistance at the various stages of installation.

Remember to compare the resistance readings with the information provided on the product tag, box, or manual, as each heater model has its specific resistance values. Keep thorough records of the heater model number, core-to-core resistance readings, and resistance readings for each leg-to-ground. These records will be necessary for warranty registration.

If you encounter any deviations or discrepancies during the testing process, please don’t hesitate to contact us for assistance. Our team is ready to provide further instructions and support to ensure the success of your floor heating system. To access our support services, simply reach out to us at (888) 927-6333 or ussales@warmup.com


Thermostats
Underfloor Heating Thermostats
Electric Systems
Heated Floors

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