I am constantly finding 240v line voltage programmable thermostats that are "under heating". Room temperature is quite below the temperature indicated on the thermostat. They appear to be maintaining their setting temperatures, as judged by their own readout, but I finally realized with an infraRed gun that the thermostat box itself was often 10 deg C hotter than the wall adjacent. I further identified that this "heated box" syndrome was hotter when it was controlling more power -- ganged baseboards. I am getting nothing from the manufacturers. This is happening with several models of Aube but I have received complaints of other brands also maintaining room temperature considerably below the set points. Is it possible that the wiring itself inside the box behind the thermostat is heating the thermostat and kicking out before the ambient temperature is reached? When I look behind the problem thermostats there appear to be a pretty tightly packed set of wires.