In the north antifreeze is ethylene glycol (propylene glycol or propylene glycol) antifreeze. According to the latitude of different selection of different freezing point of the heat transfer medium.
South of the Yangtze River to use in -10 ℃ system will not freeze antifreeze.
North of the Yangtze River to use in -20 ℃ system will not freeze antifreeze.
North of the Yellow River to use in -30 ℃ system will not freeze antifreeze.
Make sure that the system will not freeze ice in winter.
In Yunnan and other places also use pure water as a heat transfer medium.