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[Michelle J]

Warmup UFH laid about 10 years ago, working fine but supply unit humming terribly and was replaced a few weeks ago. Since then only a third of the heating area gets warm. Electrician has reviewed the wiring of the supply unit and done a resistance check and everything seems in order. Suggestions please!

 

[DefyG]

Is it a large area, as more than one heating mat may have been installed.
If one is 'open circuit' the other(s) will still work but it should show up on a resistance check!
Have you the original test results to check against?

 

[Michelle J]

Is it a large area, as more than one heating mat may have been installed.
If one is 'open circuit' the other(s) will still work but it should show up on a resistance check!
Have you the original test results to check against?

It is a large kitchen and conjoined utility area. The utility area and about 2 feet into the kitchen works (1/3rd of the total). I don't have the original results to check against. The electrician who replaced the supply unit came back and checked the wiring and said that it was an open circuit. He's scratching his head and asking his colleagues.

 

[telectrix]

possibility is that if there are 2 mats there may be 2 in floor sensors. if so and both have been wired into a thermostat that only requires 1 sensor, that could cause your problem. the solution would be to diss. 1 sensor from the stat and rely on the other one.

 

[Michelle J]

possibility is that if there are 2 mats there may be 2 in floor sensors. if so and both have been wired into a thermostat that only requires 1 sensor, that could cause your problem. the solution would be to diss. 1 sensor from the stat and rely on the other one.

Thanks for that, I'll pass it on to the electrician! As far as I'm aware the sensor/thermostat setup is as per original installation, but he'll know for sure.