IB> 'when' it fails. I did it
this way as I didn't know what the big resistor did that is part of the
thermostat.
"Wall thermostats, when fitted, are in series with the CH signal
from the time-switch. Some have a built in resistor ("accelerator heater")
t
reduce the hysteresis, i.e. the "backlash" in temperature between switching
on
and switching off. When the thermostat is on, the resistor supplies a
minute
amount of heat, which makes the thermostat think that the room is slightly
warmer than it is, and therefore makes it switch off again earlier. The
room
temperature will thus fluctuate less. Such thermostats require 3 cores and
earth: live, switched output and neutral for the resistor. If live and
switched output are interchanged, the resistor will be powered constantly
and
the advantage will be lost. Simpler/older thermostats only need 2 cores and
earth, so if you're replacing a thermostat you might want t check the
wiring
beforehand to see if you can use this feature. "
James H