18 weeks old. The pullets are solid black with a top knot. The roos are barred all over black and white. They look similar to a Barred Rock. I'll takes some pictures and post them.
If in series and one stat fails in the open position electrical current can not flow thru the second stat and on to the heat element. On my incubators I use an inexpensive digital thermostat with an output visual/audio alarm. By the way I am a retired electronics professor.