For freeze protection, the required concentration of inhibited glycol fluid in a system depends on the operating conditions of the system and the lowest expected ambient temperature. Dry Coolers has ability to look up the winter extreme low condition for your geographic location. Contact us to help you determine the cold temperature design point. For corrosion protection, it’s also important to consider the materials of construction, the age of the system and other variables. Your local glycol supplier representative can help you analyze the specific requirements for your system.

We strongly recommend you purchase the glycol pre-mixed and avoid the chance of adding improper diluted glycol solution to your system. 

DO NOT USE AUTOMOTIVE ANTI-FREEZE. Coolants for automobiles have inhibitors based on aluminum. Their inhibitor package is wrong for our industrial cooling systems.

The table below shows the protection from freeze damage provided by various concentrations of DOWFROST propylene glycol inhibited fluids. To determine the concentration required, select the lowest expected ambient temperature and decide whether the cooling system requires freeze protection to keep it pumpable, or burst protection to simply prevent damage from fluid expansion.

As a further measure of protection against dilution error, or unexpected cold temperatures, select a temperature that is at least 5°F colder than the lowest expected ambient temperature. If, for example, the lowest expected temperature is -15°F, select the line in the table below for -20°F. The table shows that at this temperature, a solution of 45% DOWFROST is required for freeze protection. A concentration of 30% is needed to provide burst protection at this temperature.

PERCENT VOLUME GLYCOL CONCENTRATION REQUIRED 

Source: Dry Coolers