Glycol Concentration Calculator:
Freeze & Burst Protection

Use our Concentration Calculator to determine the required concentration of inhibited glycol fluid needed for your desired cold weather protection.

Please Note:

  • DOWTHERM™ SR-1 is not available in concentrations below 25% as ethylene glycol solutions less than 25% may be at risk for bacterial contamination.
  • If you require freeze point protection for temperatures between -28°F and -60°F, contact us to determine a custom concentration. For temperatures below -60°F, contact us to explore an alternative solution that is right for your system.
  • If you require burst point protection for temperatures between -28°F and -60°F, the necessary concentration is 35% for all three glycol products.

What is Freezing Point Protection (Freeze Protection)?

Freeze protection is required in hydronic HVAC systems where fluid must continue pumping at the lowest anticipated temperature. This is in applications where no ice crystals can be permitted to form, or where there is inadequate space for expansion of an ice/slush mixture.

When we discuss freezing point protection, we are determining the coldest temperature at which the system fluid must continue functioning with little to no ice/slush mixture. We protect up to the lowest anticipated temperature (also known as the freezing point) by adjusting the antifreeze mix ratio, or the concentration of glycol in the heat transfer fluid. The higher the concentration, the colder the mixture will continue to protect.

Note that you should only protect up to the lowest anticipated temperature and no further, as there is a trade-off between efficiency and concentration. Excess concentration will impact maximum heat transfer efficiency.

Other appropriate applications for freeze protection would include:
  • HVAC systems that are subject to prolonged winter shutdown but must start-up again while the weather is still cold.
  • Closed-loop systems that must be protected in the event of power or pump failure.

What is Burst Point Protection (Burst Protection)?

Burst protection is sufficient if the hydronic HVAC system will remain dormant or inactive when the temperature drops below freezing and there is adequate space to accommodate the expansion of an ice/slush mixture. You may not be able to pump this slush, but your system will not burst.

When we discuss burst point protection, we are determining the coldest temperature at which the system fluids will become ice/slush, but doesn’t freeze and expand enough to burst the piping and coils. We protect up to the lowest anticipated temperature (also known as the burst point) by adjusting the antifreeze mix ratio, or the concentration of glycol in the heat transfer fluid. The higher the concentration, the colder the mixture will provide protection.

Glycol Concentration Charts

Propylene Glycol Freeze Chart

Ethylene Glycol Freeze Chart