Keeping propylene glycol from freezing in my solar thermal system.

A: How do I prevent my glycol from freezing during those rare deep freeze nights?
Q: Your glycol, although rated for very low temperatures may be un-pumpable at a temperature higher than you expect. This can cause you system to overheat when the sun comes out in the morning. To prevent this you can activate the antifreeze function in your SmartMaxx controller. This function will turn the pump on as soon as your sensor 1 reaches a pre determined temperature, say -5 degrees. This will run only for a few minutes and then turn off, thus keeping your glycol above the un-pumpable temperature.