Selecting The Proper Concentration

The concentration of glycol-based heat transfer fluid required in a system depends on the kind of protection needed in winter, or the operating temperature if the system involves refrigeration. There are two basic types of protection available: "burst protection" and "freeze protection." 

Burst protection 

Burst protection is sufficient if the system will remain dormant when the temperature is below the freezing point of the solution. In HVAC applications, burst protection is considered an: appropriate safeguard in systems when there is adequate space to accommodate the expansion of an ice/slush mixture and the system is inactive during the winter.

Inhibited glycol-based fluids provide burst protection in the following manner: as the temperature drops below the solution's freezing point, ice crystals begin to form. Because water in the solution freezes first, the remaining glycol solution becomes further concentrated and remains fluid. The combination of ice crystals and fluid results in a flowable slush. Fluid volume increases as this slush forms, with the extra volume flowing into available expansion volume in the system. If the concentration of glycol is sufficient, system damage will not occur.

For burst protection, a 30 percent (by volume) solution of ethylene glycol (31.4 percent CS-l00 or 32.5 percent CS-400) is usually adequate, See Table below for typical ethylene glycol concentrations required to achieve burst protection at various temperatures.

 Freeze protection

Freeze protection is required in systems where fluid must be pumped at the lowest anticipated temperature. Freeze protection is essential in cases where no ice crystals can be permitted to form or where there is inadequate expansion volume available to accommodate ice/slush formation.

For freeze protection, the required concentration of inhibited glycol fluid in the system depends on the operating conditions of the system and the lowest expected ambient temperature. HVAC systems that are subject to prolonged winter shut-down - but which must start-up again while the weather is still cold -  may require freeze protection. Freeze protection is also appropriate for closed-loop systems that must be protected in the event of power or pump failure.

To obtain adequate freeze protection the glycol solution must maintain a freezing point at least 5°F below the lowest  anticipated ambient temperature. See Table below for typical concentrations of CSI fluids required to provide freeze protection. 

Typical Concentrations of CSI Fluids Required to Provide Freeze and Burst Protection at Various Temperatures *

*  A certificate of analysis will be provided upon request.