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Glycol Freeze Protection Calculator

Local glycol freeze and burst planning rows with product-data, test-method, code, and qualified-review warnings

Field guide: Expansion Tank Sizing for Hydronic Systems: Planning Method

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Glycol service kit

Fluid, testing, and fill products for glycol freeze-protection checks:

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Free glycol freeze protection planning calculator for HVAC technicians and hydronic system designers. Enter a target freeze point or known concentration to estimate local propylene- or ethylene-glycol rows, heat-capacity derating, density, viscosity factor, burst-temperature context, and Cp-only flow correction. The local rows are source-gap planning data, not current ASHRAE table or Dow product-data-sheet reproductions.

Pro Tip: Use the minimum concentration that can be justified by the actual product data, tested concentration, design temperature, and owner risk tolerance. High glycol concentration can create pump, heat-transfer, viscosity, inhibitor, and maintenance penalties, so final selections need current product data and system-specific review.

Size the expansion tank for a glycol-filled system

Expansion Tank Sizing Calculator →

Check hydronic pipe flow with glycol caveats

Hydronic Pipe Sizing Calculator →

Check psychrometric properties at design conditions

Psychrometric Calculator →

How It Works

  1. Select Glycol Type

    Choose propylene glycol or ethylene glycol for an estimate only. Ethylene glycol is toxic, and potable-water, cross-connection, food-contact, and occupied-building acceptance must be checked against current code, SDS, product, and AHJ requirements.

  2. Choose Your Mode

    Use "Find concentration" to enter a target freeze point and check the local concentration row, or use "Analyze concentration" to enter a known tested concentration and view local-row properties.

  3. Review Source Gaps

    The calculator shows specific heat, density, viscosity multiplier, heat-capacity derating, and a Cp-only flow correction. Replace those local rows with current product data and full pump/pipe/heat-exchanger review before final design.

Built For

  • HVAC contractors screening glycol assumptions before product and code verification
  • Mechanical engineers documenting preliminary glycol concentration cases for hydronic loops
  • Service technicians comparing tested concentration against local planning rows after dilution or makeup water
  • Solar thermal installers flagging freeze and burst assumptions that need current product data
  • Facility engineers documenting propylene glycol source gaps before potable-water or food-contact review

References

  1. ASHRAE 2025 Handbook Fundamentals source pointer for property-table context
  2. Dow DOWFROST heat transfer fluid product source pointer
  3. Dow DOWTHERM SR-1 heat transfer fluid product source pointer
  4. NIOSH Pocket Guide ethylene glycol source pointer for chemical-safety context
  5. Adopted mechanical code, product data, SDS, and AHJ review for final acceptance

Frequently Asked Questions

Freeze point and burst protection are different product-table concepts. The app reports both from local planning rows, but final decisions should use the current fluid data sheet, concentration scale, tested concentration, product family, and owner risk tolerance.
Propylene glycol is commonly selected where lower toxicity is important, while ethylene glycol is toxic and requires chemical-safety, cross-connection, SDS, code, and AHJ review. The app does not approve either fluid for a specific system.
The app displays a Cp-only flow correction as an estimate. Real flow, pressure drop, and heat transfer also depend on density, viscosity, temperature, Reynolds number, pipe/fittings, pump curve, heat exchanger, controls, and product data.
Glycol condition can change with heat, oxygen, water quality, contamination, inhibitor depletion, and makeup water. Verify concentration, pH/reserve alkalinity, corrosion inhibitors, and replacement or re-inhibition requirements against the product data and site maintenance program.
Disclaimer: This tool provides preliminary source-gap planning output only. It is not a licensed ASHRAE table reproduction, product data sheet, potable-water or food-contact approval, ethylene-glycol handling approval, mechanical-code/AHJ approval, pump or heat-exchanger selection, spill response, or final hydronic design.

Guides for this job

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Expansion Tank Sizing for Hydronic Systems: Planning Method

How to size diaphragm expansion tanks using the ASHRAE formula. Gauge vs absolute pressure, glycol correction factors, system volume estimation, and common sizing errors.

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Glycol Freeze Protection: Concentration, Performance, and Source Gaps

Selecting the right glycol concentration for freeze protection without over-concentrating. Freeze vs burst point, viscosity penalties, heat transfer derating, and annual maintenance.

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