I have heat mats installed under the tile flooring in my chalet. It is only used several times a year and stays around 50 degrees while we are gone. They have stopped working and the tile guy says it is because the house gets too cold and when we come to use it we crank up the mats and they cannot take the load. Is it uncommon to have this problem?

Is the tile person suggesting a breaker is tripping or the wire in the mat is bad?