This control is also called a "bonnet control" in
conventional house gas and oil furnaces. It has a very sensitive
Bi-Metal element probe which senses differences in temperature. The
bonnet control is positioned such that the probe senses the metal
temperature of the heat exchanger surfaces of the JUCA. When it
senses that warmed air is present there, it closes a switch
which turns on the JUCA's blower to distribute the warm air out
into the room.
At whatever point that you let the fire go out, the probe senses that, as well, and shuts the blower off to save electricity. The ON temperature is pre-set at 110°F and the OFF temperature is pre-set at 90°F, so the blower automatically turns on and off at appropriate times for most efficient operation. The settings are NOT adjustable.
JUCAs are built very sturdily, to easily withstand hours or days of operation with the blower off (due to no electricity ow when you just want a fire but minimal heat). (Under those circumstances, the unit's overall efficiency drops a lot, but it can still provide emergency heat.)
This control is a common heating switch, so if many years from now, you ever needed to replace it, a local heating store would have it.
The JUCA Home Page is at:
http://mb-soft.com/juca/index.html
E-mail to: JUCA1@mb-soft.com