Glycol concentration decisions should start with the actual fluid product, tested concentration, expected temperature exposure, inhibitor condition, code/AHJ requirements, and equipment limits. Higher concentration can improve freeze or burst margins but can also increase viscosity, reduce heat capacity, and change pump and heat-exchanger performance.
This guide explains local planning concepts for propylene glycol and ethylene glycol, but it is not a current ASHRAE table reproduction, Dow product-data-sheet reproduction, potable-water or food-contact approval, ethylene-glycol handling approval, or final hydronic design. Verify final selections against current product data, SDS, field testing, adopted code, and qualified review.
Freeze Point vs. Burst Protection
Freeze point and burst protection are different product-table concepts. Freeze point is generally the point where ice crystals begin forming; burst protection is a separate lower-temperature damage screen for some product tables and test conditions.
The app displays a small local row set for screening, but those rows are not current licensed ASHRAE tables or product data sheets. Final freeze and burst decisions should use the specific fluid manufacturer data, concentration test method, product family, inhibitor package, water quality, exposure duration, pipe/equipment vulnerability, and owner risk tolerance.
Glycol Freeze Protection Calculator
Determine required glycol concentration for freeze protection with performance penalties. Propylene and ethylene glycol data from ASHRAE Fundamentals Ch. 31 and Dow Chemical.
The Performance Penalties of Glycol
Glycol concentration affects specific heat, density, viscosity, corrosion protection, and maintenance. The app uses local rows to show a heat-capacity derating and a Cp-only flow correction, but real system effects also depend on temperature, Reynolds number, pipe and fitting pressure drop, pump curve, heat exchanger, controls, and product chemistry.
For final design, replace the local planning rows with the product data sheet or engineering software for the specific fluid and temperature range. Then check pump head, heat-exchanger capacity, strainers, valves, expansion tank, relief controls, air elimination, and low-temperature startup behavior.
Propylene vs. Ethylene Glycol
Propylene glycol is commonly selected where lower toxicity is important. Ethylene glycol can have performance advantages in some industrial systems, but it is toxic and requires SDS review, exposure-control review, spill-response planning, storage/disposal controls, cross-connection review, and code/AHJ acceptance.
The app does not approve either fluid for a specific system. Potable-water heat exchangers, food-service systems, occupied buildings, industrial processes, solar loops, and process cooling systems can have different product, code, insurance, owner, and safety requirements.
Testing and Maintenance
Glycol condition can change with temperature, oxygen exposure, metals, water quality, dilution, contamination, and inhibitor depletion. A concentration reading alone does not prove corrosion protection, compatibility, or fitness for continued service.
Maintenance decisions should follow the fluid manufacturer procedure and the site program, including the correct refractometer scale or lab method, pH/reserve alkalinity, inhibitor condition, corrosion metals, biological growth where relevant, water quality, makeup history, and replacement or re-inhibition criteria.