Does Your Chiller Need Antifreeze?
Last Updated: Originally published July 9, 2003. Summary: This guide explains when chillers require antifreeze, what types are appropriate, how freezing can damage a system, and how glycol concentrations affect chiller performance. It also includes recommendations on coolant selection, system materials, concentration limits, and maintenance considerations, exactly as discussed in the article.
Link to Does Your Chiller Need Antifreeze
Quick Facts
Why Antifreeze Is Needed:
- Prevents flash freezing of plates in the evaporator
- Prevents cracking and leaks in heat exchangers
- Protects equipment from low-ambient and freezing process conditions
Indicators You Need Antifreeze:
- Chiller is exposed to freezing ambient temperatures
- Leaving chilled-water temperature is 50°F (10°C) or below
- System may experience flash freezing in the evaporator
Recommended Glycol Types:
- Ethylene glycol — preferred for most chillers
- Propylene glycol — required for pharma, food, potable water, or where regulations prohibit ethylene glycol
- Glycol temperature ranges: –60°F to 350°F (–51°C to 177°C)
Do NOT Use:
- Automotive antifreeze (can foul heat exchangers and reduce heat transfer)
Why Antifreeze Is Necessary
- “Your chiller system can suffer flash freezing or serious damage when exposed to freezing conditions.” — Rex Martin, Tecumseh Products Co.
Problems caused by freezing:
- Loss of system efficiency
- Plate freezing in the evaporator
- Cracks in heat exchanger plates
- Leaks caused by freezing expansion
“Antifreeze used in proper concentrations will keep flash freezing from occurring and reduce the possibility of chiller failure.”
Types of Antifreeze to Use
Ethylene Glycol
- Preferred coolant for most chiller applications
- Not acceptable in some states or where contamination risks exist
Propylene Glycol
- Required for pharmaceutical, food, and potable-water-adjacent applications
- Must be clear; dyed or specially inhibited glycols are toxic and not permitted for contact with those processes
Never Use Automotive Antifreeze
- Additives can foul heat exchangers
- Significantly reduces heat transfer
System Construction Considerations
System piping materials affect corrosion risk:
- Not Recommended:
- Iron
- Steel
- Galvanized piping
- (Can suffer corrosion and pitting even with inhibited glycol.)
- Recommended:
- Copper
- Stainless steel
- Schedule 80 PVC
How Antifreeze Affects Performance
- Antifreeze reduces chiller efficiency depending on concentration.
- “BTU output is reduced as the concentration of glycol is increased.”
- Do not exceed:
- 50% propylene glycol by weight
- 40% ethylene glycol by weight
- Glycol changes:
- Cooling capacity
- Pump flow rates
- System pressure drop
- System design engineers use correction factors to size new chillers. (Referenced in Tables 1 & 2 of the article.)
Retrofitting an Existing System
- If you have a 5-ton chiller and need 5 tons of cooling, you must account for the reduction in output caused by glycol.
- Review:
- Chiller settings
- Actual process heat load
- Cooling requirements
- Adjust the process to compensate for the reduced cooling caused by glycol addition.
Lowest Safe Operating Temperature
- Dependent on:
- Water quality
- System design efficiency
- Some systems can operate as low as 47°F (8°C), while others require settings as high as 60°F (16°C) to avoid freezing.
Maintaining Correct Antifreeze Strength
Once antifreeze is mixed into the system:
- Keep premixed antifreeze on hand (5-gallon buckets or drums).
- Loss of water from leaks, spills, or evaporation can change concentration.
- Technicians should add premixed solution — avoids guessing required antifreeze amounts.
- Helps maintain the correct freeze point.
Maintenance Frequency
- Antifreeze concentration should be checked periodically.
- Frequency depends on the system type and water-loss rate.
- Follow the manufacturer's recommended maintenance schedule.
Contact & Support
For chiller or coolant recommendations:
📞 734-855-4890
📧 support@usalabequipment.com