Why are my floor heating system resistance readings not the same after several years?
It is very uncommon for a mat to fail over time. Because there are no moving parts and no leaking or freezing liquids, systems will last a very long time. However, if repairs are done to the floor, fixed furniture or any related area in the room, damage can be done to the cable and needs to be addressed. Common instances are trim work, tile repair, grout cleaning, and door stops.
It is not impossible that a slight cable damage was not spotted during the installation and reveals itself as a break or ground leak after a few weeks or months of operation. Again, this is uncommon, but possible. In the event that you find yourself with resistance readings that are off and you would like to investigate further, a TDR meter can help find the issue if you know the heater model number. Warmup does rent TDR meters for customers in need but customers must be willing to remove flooring and make a repair for the TDR to be successful.