Glycol Calculator
Calculate glycol concentrations for freeze protection in hydronic heating, chilled water, solar, and geothermal systems. Includes viscosity effects, heat transfer penalties, and cost analysis.
System Parameters
Lowest ambient temperature expected
Normal system operating temperature
Additional protection margin
Cost Analysis
Current local glycol price
Recommended glycol replacement frequency
Advanced Options
Quick Reference Guide
Typical Concentrations
- • 20-30%: Mild climate protection
- • 30-40%: Moderate freeze protection
- • 40-50%: Cold climate systems
- • 50%+: Extreme cold applications
Temperature Ranges
- • Mild: 20°F to 32°F (-7°C to 0°C)
- • Moderate: 0°F to 20°F (-18°C to -7°C)
- • Cold: -20°F to 0°F (-29°C to -18°C)
- • Extreme: Below -20°F (-29°C)
Maintenance Notes
- • Test concentration annually
- • Monitor pH levels (7.5-10.5)
- • Use inhibited glycol only
- • Replace every 3-5 years
Glycol System Guidelines & Best Practices
System Design
- • Size pumps for increased viscosity
- • Account for reduced heat transfer
- • Use corrosion-resistant materials
- • Install proper expansion tanks
Safety & Handling
- • Use propylene glycol for potable systems
- • Avoid ethylene glycol near drinking water
- • Proper ventilation during mixing
- • Follow local disposal regulations
Performance Optimization
- • Minimize glycol concentration
- • Consider insulation alternatives
- • Use high-efficiency circulators
- • Regular system maintenance
Frequently Asked Questions
What's the difference between propylene and ethylene glycol?
Propylene glycol is food-grade and safe for potable water systems, while ethylene glycol is toxic but provides better freeze protection. Use propylene for hydronic heating and ethylene for closed industrial systems.
How does glycol affect pump sizing?
Glycol increases fluid viscosity, requiring more pumping power. At 50% concentration, you may need 25-50% more pump capacity depending on temperature and glycol type.
How often should I test and replace glycol?
Test glycol concentration and pH annually. Inhibited glycol typically lasts 3-5 years in closed systems. Replace if concentration drops significantly or pH goes outside 7.5-10.5 range.
Can I use automotive antifreeze in my heating system?
Never use automotive antifreeze in HVAC systems. It contains silicates and other additives that can damage pumps and heat exchangers. Use only HVAC-grade inhibited glycol.
What concentration should I use for my system?
Use the minimum concentration needed for freeze protection plus a 5-10°F safety margin. Higher concentrations reduce efficiency and increase costs with minimal benefit.
How often should glycol concentration be tested and maintained?
Test glycol systems at least annually, ideally before heating season starts. Over time, glycol breaks down from heat cycling and can become acidic, corroding your system from the inside. You'll also lose glycol gradually through small leaks and evaporation. Most systems need a glycol top-off every 2-3 years and complete replacement every 5-10 years depending on system temperature and maintenance.
Related System Design Calculators
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Size expansion tanks for glycol-filled closed-loop heating systems.
Pipe Volume Calculator
Calculate total system volume to determine glycol mixture quantities.
BTU Heating Load Calculator
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Pump Head & Power Calculator
Account for increased viscosity when sizing pumps for glycol systems.
Pipe Insulation Heat Loss
Calculate heat loss in glycol distribution lines to optimize efficiency.
Hot Water Recirculation
Design recirculation systems for indirect water heating with glycol boilers.
Complete Your Glycol System Design
Glycol systems require careful design considerations. Use these calculators for comprehensive system analysis: