Why would a manufacturer depend on the temperature thermistor that cycles the chiller for freeze protection? Yesterday I went out on a MR chiller and found the Glycol running at 2F, everything was iced up. It had locked up the Cold head compressor and one of the LCC Gradient pumps was locked up.

The discharge Glycol/water thermistor went bad and was reading 80F, full speed head at 2F.

Seems like a cheap old Penn control would solve the problem, but its probaly cost $40.