Is Glycol a Refrigerant? Uses, Safety, and How It Works in Cooling Systems
What Is Glycol and How Is It Used in Cooling Systems?
Glycol is a type of chemical compound that belongs to the alcohol family and is best known for its antifreeze and heat transfer capabilities. The two most commonly used types of glycol in refrigeration and HVAC systems are:
- Ethylene Glycol: Known for its excellent thermal properties but toxic to humans and animals.
- Propylene Glycol: Safer and food-grade, widely used where toxicity is a concern (e.g., food processing plants).
Glycol itself is not a refrigerant in the traditional sense. Instead, it is a secondary coolant or heat transfer fluid used in cooling systems to absorb and transfer heat. It is typically mixed with water to form a glycol solution that prevents freezing and protects equipment from damage in cold temperatures.
Applications of Glycol in Cooling
Glycol solutions are used extensively in:
- HVAC systems: especially in chilled water and hydronic systems
- Industrial refrigeration: including food and beverage production lines
- Ice rinks and sports arenas
- Pharmaceutical manufacturing
- Brewery and winery operations
The glycol solution circulates through pipes and heat exchangers to remove heat from the environment or processes, transferring it to a primary cooling source, usually a chiller.
For more technical details on glycol types and properties, see Engineering Toolbox – Glycol Solutions.
How Glycol Works in Closed-Loop Refrigeration Systems
Glycol typically functions in a secondary loop refrigeration system, which works alongside a primary refrigerant loop. Here’s how it operates step-by-step:
- A primary refrigerant (like R-134a or R-410A) is compressed, condensed, expanded, and evaporated in a chiller, absorbing heat from the glycol solution inside a heat exchanger.
- The chilled glycol solution is then pumped through a closed piping network to various equipment or spaces that require cooling.
- The glycol absorbs heat from these areas and returns to the chiller to be cooled again.
- The cycle repeats continuously.
This secondary loop design isolates the primary refrigerant from the cooled space, offering several advantages such as reduced refrigerant charge, easier maintenance, and minimized risk of refrigerant leaks in the occupied areas.
Why Use Glycol in Secondary Loops?
- Freeze Protection: In cold climates, glycol solutions prevent water in pipes from freezing and causing damage.
- Safety: Using glycol as a secondary fluid reduces the quantity of refrigerant in occupied or sensitive areas.
- Flexibility: Secondary loops can be extended with less risk of refrigerant loss or environmental contamination.
This system design is common in large commercial buildings, data centers, ice arenas, and food processing plants.
You can find a detailed explanation of secondary loop systems on ASHRAE’s website.
Advantages and Limitations of Using Glycol
Advantages
- Freeze and Burst Protection: Glycol lowers the freezing point of water, preventing pipe freeze and burst even in very cold environments.
- Corrosion Inhibitors: Modern glycol formulations include additives to protect metal pipes and components from corrosion.
- Chemical Stability: Glycol solutions maintain their properties for long periods under controlled conditions.
- Non-Volatile: Unlike refrigerants that vaporize easily, glycol remains liquid, reducing leakage risk and environmental impact.
Safety (Propylene Glycol): Non-toxic and food-grade options allow use in sensitive environments.
Limitations
- Reduced Heat Transfer Efficiency: Glycol solutions generally have lower thermal conductivity and heat capacity than pure water or direct refrigerants, which may require increased pumping energy.
- Toxicity of Ethylene Glycol: Although efficient, ethylene glycol is toxic and must be handled with care to avoid contamination.
- Degradation Over Time: Glycol breaks down, especially when exposed to oxygen and high temperatures, forming acids and sludge that harm system components.
- Regular Maintenance Needed: Glycol concentration, pH, and inhibitor levels must be routinely tested and adjusted for system longevity.
Because of these trade-offs, proper glycol management—including testing and replacement—is crucial for system performance.
For glycol testing and maintenance protocols, visit CoolSys Glycol Testing.
Glycol vs. Traditional Refrigerants: What's the Difference?
It’s important to understand that glycol and refrigerants serve different roles in cooling systems:
Aspect | Glycol | Traditional Refrigerants |
Role | Secondary coolant / heat transfer fluid | Primary refrigerant gas/liquid |
Cooling Mechanism | Transfers heat without phase change | Absorbs heat via phase change (liquid↔gas) |
Common Substances | Ethylene glycol, propylene glycol | R-134a, R-410A, CO2, ammonia |
Usage | Secondary loops and heat exchangers | Compressors and evaporators |
Toxicity and Safety | Propylene glycol is food-safe | Varies; some refrigerants are toxic or GHGs |
Environmental Impact | Low direct emissions | Regulated for ozone depletion & GWP |
Key Point:
Glycol is not a refrigerant by itself. It is used to transfer cold from a primary refrigerant to the cooling load safely and efficiently.
This secondary loop arrangement is especially valuable for protecting the environment and improving system safety in sensitive applications.
Brilliant Wrap-Up: So, Is Glycol Really a Refrigerant?
The short answer: No, glycol is not a refrigerant. Instead, glycol is a critical heat transfer fluid used in refrigeration and HVAC systems to safely and efficiently carry cooling between the chiller and the cooled space or equipment.
Its primary benefits include:
- Providing freeze protection for pipes and equipment in cold environments.
- Enhancing safety by reducing the amount of primary refrigerant in occupied spaces.
- Offering corrosion protection and extending equipment life.
- Allowing flexible system design with reduced refrigerant charge.
Understanding the distinct roles of glycol and refrigerants helps facilities managers and engineers design better cooling systems that balance efficiency, safety, and environmental compliance.
Need a reliable partner?
Red River specializes in the design and manufacturing of pressure vessels. We also fabricate related items such as prefabricated spools and skid packages.
Reach out to us today and experience the Red River difference. Where American-made products and American Values come together, we care more.
Frequently Asked Questions
1. Is glycol a type of refrigerant?
No, glycol is a heat transfer fluid used alongside refrigerants but does not function as a refrigerant itself.
2. What is the difference between ethylene glycol and propylene glycol?
Ethylene glycol is efficient but toxic. Propylene glycol is safer and food-grade but less efficient thermally.
3. Can glycol be used in residential HVAC systems?
While uncommon, glycol is sometimes used in radiant heating or in systems requiring freeze protection.
4. Why use glycol in refrigeration systems?
Glycol prevents freezing, protects pipes, and transfers chilled fluid safely in secondary loop systems.
5. How often should glycol solutions be tested?
Testing is recommended at least annually, though semi-annual checks ensure optimal pH, concentration, and inhibitor levels.
6. Does glycol degrade over time?
Yes. Exposure to heat and oxygen breaks glycol down, requiring regular monitoring and replacement.
7. Is glycol environmentally friendly?
Propylene glycol is generally safe for the environment, while ethylene glycol must be handled carefully due to toxicity.
8. What happens if glycol concentration is incorrect?
Too low concentration risks freezing and corrosion; too high concentration reduces heat transfer efficiency and increases pumping energy.
Key Takeaways
- Glycol is not a refrigerant but a secondary coolant that transfers heat in refrigeration systems.
- There are two main types: ethylene glycol (toxic, efficient) and propylene glycol (safe, food-grade).
- Glycol solutions prevent pipe freezing and help extend the lifespan of refrigeration systems.
- Used primarily in secondary loop cooling systems to improve safety and flexibility.
- Requires regular testing and maintenance to ensure system efficiency and prevent degradation.
- Understanding glycol’s role helps optimize system design, ensuring safer, more sustainable cooling.
Solutions
In the realm of industrial solutions, Red River emerges as a pioneer, offering a diverse range of custom-engineered products and facilities. Among our specialties is the design and production of Custom/OEM Pressure Vessels, meticulously crafted to meet individual client requirements, ensuring performance under various pressure conditions. Our expertise extends to the domain of prefabrication, where Red River leads with distinction.
The company excels in creating prefabricated facilities, modules, and packages, reinforcing its stance as a forerunner in innovation and quality. This proficiency is further mirrored in their Modular Skids offering, where they provide an array of Modular Fabricated Skid Packages and Packaged equipment. Each piece is tailored to client specifications, underlining their commitment to delivering precision and excellence in every project they undertake.
