Hi. This is my first winter raising chickens and I'm using a light bulb in a metal can to keep their water from freezing. Well, it was 22 degrees this morning and three of my six waterers were frozen. The bulbs had burned out. I find it strange. Also, each light is connected to a Thermo Cube, which is a thermostatically controlled plug. Any comments on this would be appreciated and what do you use to keep the water from freezing? Thanks.