Help with modified radiant floor system

[Mr. P]

We recently had a radiant floor heating system (ProHeat) installed under a marble tile floor in our master bathroom. This is a line voltage system with a thermostat mounted in the wall. When the contractor finished the job, the system didn't work, and further investigation led us to find that he cut a portion of the heating cable off before finishing the tile. I was able to excavate the damaged end of the heating cable, and perform a resistance check back to the cold end of the cable, which was 8.5 ohms against the factory spec of 12 ohms at ambient temperature. The technical support at ProHeat thinks the cable was shortened significantly (~25%), and that the cable will fail quickly because it will see 13A of current instead of the 9A nominal spec. He said all we can do now is put a new splice on the end, re-install the tile, and run the system until the wire overheats and fails due to the higher current.
I'm wondering if there are any other compliant solutions, like somehow regulating the voltage at ~80 volts to keep the current closer to spec?
Thanks for the advice!

 

[Dennis Alwon]

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