Glycol Refrigeration Systems: What It Is, Benefits & Types of Glycol
Glycol refrigeration systems are important in industries that require stable, precise cooling over extended distances or across multiple zones. They use a mixture of water and glycol as a secondary fluid to transfer heat, offering greater control and safety than direct refrigerant systems. Common applications include breweries, ice rinks, food processing, and pharmaceutical manufacturing.
Instead of circulating refrigerant to each cooling point, a glycol refrigeration system keeps it contained within a central chiller. The chiller cools the glycol mixture, which is then pumped through insulated piping to various areas. A 60/40 glycol-to-water ratio is typically used to prevent freezing and ensure accurate temperature control—often within ±1°F—making the system effective for critical cooling tasks.
In this article, we’ll explore how glycol refrigeration systems operate, the differences between glycol types, and where these systems perform best. We’ll also cover key design factors, maintenance practices, and the operational benefits that make glycol refrigeration a reliable solution in commercial and industrial settings.
Glycol refrigeration uses a water-glycol mixture to transfer heat indirectly.
It supports long-loop and multi-zone systems across large spaces.
Propylene glycol is non-toxic and suitable for food-related use; ethylene glycol is more efficient but toxic.
The system reduces refrigerant charges and offers better temperature consistency over distance.
Proper maintenance, glycol testing, and system design are essential for optimal performance.
What is glycol refrigeration?
Glycol refrigeration is a type of indirect refrigeration system where a water-based solution of glycol is used to carry heat away from the product or process being cooled. Unlike direct refrigeration, which uses refrigerant flowing directly through coils in the cooled area, glycol systems circulate a secondary fluid—typically propylene or ethylene glycol—that absorbs heat and transfers it to a primary refrigeration unit.
This indirect method allows for safer, more controlled temperature management across multiple zones or long distances, making it especially useful in complex facilities.
How glycol refrigeration systems work
Glycol refrigeration relies on a closed-loop circuit that includes a chiller, a glycol reservoir, circulation pumps, and a network of insulated piping. Here’s how it functions step-by-step:
Primary chiller cools the glycol mixture to the desired setpoint using a standard refrigeration compressor and evaporator.
Cooled glycol is pumped through insulated lines to remote cooling coils, heat exchangers, or process equipment.
Heat is absorbed from the target area or product, raising the temperature of the glycol.
The warmed glycol returns to the chiller to be cooled again, and the cycle repeats.
This separation between the refrigerant and the process fluid minimizes the risk of leaks, especially in food or cleanroom environments.
Glycol acts as a secondary coolant in refrigeration systems, preventing freezing and improving heat transfer. The two most common types used in commercial and industrial applications are propylene glycol and ethylene glycol. Choosing the right type depends on the specific requirements of the system, including safety, temperature range, and industry regulations.
What is propylene glycol?
Propylene glycol is a non-toxic, food-grade glycol widely used in applications where there is potential for human contact. It is classified as Generally Recognized As Safe (GRAS) by Health Canada and the FDA when used in indirect contact with food.
Key features of propylene glycol:
Non-toxic and biodegradable, making it safe for food and beverage processing.
Used in breweries, dairies, wineries, and pharmaceutical environments.
Offers moderate thermal efficiency, slightly lower than ethylene glycol.
More viscous at low temperatures, requiring careful pump sizing.
Contains corrosion inhibitors to protect metal piping and equipment.
Propylene glycol is the preferred choice when safety and compliance with health regulations are priorities, especially in systems with a risk of incidental contact with consumable products.
What is ethylene glycol?
Ethylene glycol is a petroleum-based compound with higher thermal efficiency than propylene glycol. However, it is toxic to humans and animals, making it unsuitable for food or beverage processing applications.
Key features of ethylene glycol:
Toxic, requiring strict handling procedures and leak monitoring.
Provides superior heat transfer performance, improving system efficiency.
Lower viscosity at cold temperatures allows easier circulation with smaller pumps.
Not suitable for use where there's any risk of exposure to people, animals, or food.
Ethylene glycol is ideal for closed-loop systems in non-food environments where performance and low-temperature flow are more critical than toxicity concerns.
Propylene glycol vs ethylene glycol: What's the difference?
Property
Propylene Glycol
Ethylene Glycol
Toxicity
Low (food-safe)
High (poisonous)
Heat Transfer
Moderate
Higher
Viscosity
Higher
Lower
Common Use
Food, beverage
HVAC, industrial
Choosing the right glycol depends on system temperature, application, and health and safety requirements.
Benefits of glycol refrigeration
Glycol refrigeration systems offer several operational and safety advantages:
Long-distance cooling: Efficient heat transfer over extended piping runs.
Multi-zone temperature control: Ideal for facilities with different cooling requirements.
Freeze protection: Glycol prevents freezing in pipes, even in sub-zero conditions.
Lower refrigerant charge: Refrigerants stay in the central chiller, reducing environmental impact and compliance concerns.
System integrity: Less risk of contamination in food applications due to indirect contact.
Energy efficiency: Centralized chilling and reduced thermal loss help glycol systems deliver consistent performance with lower energy use compared to direct systems—making them a strong fit for energy efficiency marketing in industrial and commercial applications focused on reducing operating costs and environmental impact.
Applications of glycol refrigeration systems
Glycol systems are used across a wide range of sectors:
Breweries and distilleries: For fermenter cooling, crash cooling, and cold storage.
Ice rinks and curling arenas: To maintain ice surfaces through consistent sub-zero temperatures.
Food processing: Glycol is used in food processing equipment and food processing plants for hygiene and temperature control without direct refrigerant contact.
Pharmaceutical production: Maintains precise environmental controls in cleanrooms and labs.
HVAC systems: Used in large-scale commercial or institutional buildings for distributed cooling.
System design considerations
In industrial refrigeration system design, glycol systems must be carefully engineered to balance performance, safety, and energy efficiency. Key design elements directly affect the system’s ability to operate reliably over time and under varying load conditions.
Glycol concentration: Typically ranges from 30–50%, depending on the lowest expected ambient temperature. Higher concentrations offer greater freeze protection but increase fluid viscosity.
Pump selection: Must be matched to the viscosity and flow rate of the glycol mixture, especially in low-temperature environments. Proper pump sizing supports stable circulation and energy efficiency.
Pipe insulation: High-quality insulation prevents thermal losses and condensation, which helps maintain cooling performance and reduce energy consumption.
Corrosion prevention: Use inhibited glycol and regularly monitor pH (target range: 8.5–10.5) to protect components and extend system life.
Materials compatibility: Select piping and fittings that resist degradation when exposed to glycol. Avoid galvanized steel and incompatible sealants or elastomers.
Effective industrial refrigeration system design depends on thoughtful planning of each of these elements to ensure consistent cooling performance, long-term durability, and operational efficiency.
Common challenges and how to manage them
While glycol chillers offer reliable, efficient cooling in industrial and commercial settings, they require proper maintenance to perform consistently over time. Several issues can impact system reliability and efficiency if not addressed early.
1. Glycol degradation
Glycol can break down over time, especially under high heat or low pH. This leads to acidity and potential system damage. Regular testing and inhibitor top-ups are necessary.
2. Corrosion and scaling
Improperly maintained glycol can lead to rust and buildup. Use pre-mixed inhibited glycol and monitor water quality.
3. Leaks
Leaks may not always be visible. Watch for pressure drops or inconsistent cooling. Install leak detection sensors in critical areas.
4. Reduced efficiency
Old or dirty glycol loses heat transfer capacity. Filtering systems or full replacement may be needed every few years.
Best practices for installing and maintaining glycol refrigeration systems
Flush the system before adding glycol to remove contaminants and scale.
Use pre-mixed glycol solutions for consistent protection.
Test annually for pH, freeze point, and inhibitor levels.
Clean strainers and filters regularly to avoid blockages.
Monitor fluid levels and maintain expansion tanks to prevent air locks.
Keep records of maintenance activities for warranty and compliance.
Buy glycol refrigeration parts online from IRPC
Maintaining the performance and longevity of a glycol refrigeration system depends on using high-quality components that are designed for industrial environments. Common replacement parts include refrigeration pumps, refrigeration valves, heat exchangers, expansion tanks, flow sensors, and pre-mixed inhibited glycol solutions. Using parts that are compatible with glycol-based systems helps prevent corrosion, leaks, and inefficiencies over time.
For reliable, industry-grade glycol refrigeration parts, you can source key parts from IRPC (Industrial Refrigeration Parts Canada). IRPC offers a wide selection of industrial refrigeration parts specifically designed for commercial and industrial glycol systems—including parts for both new installations and retrofits. Whether you're replacing a worn-out pump, upgrading your controls, or restocking glycol fluid, IRPC supplies trusted products that meet performance and compliance standards.
Frequently Asked Questions (FAQs) about Glycol
What is the ideal glycol-to-water ratio in a refrigeration system?
The ratio depends on ambient conditions. A 40% glycol solution is common, but for colder climates, 50–55% may be required to prevent freezing.
Can I mix propylene and ethylene glycol?
No. They are chemically incompatible and mixing them can damage system components and reduce efficiency.
How often should glycol be replaced?
With regular testing and proper inhibitors, glycol can last 3–5 years. Replace sooner if pH drops or contamination is detected.
Is food-grade glycol safe for brewery refrigeration?
Yes. Propylene glycol is classified as GRAS (Generally Recognized As Safe) for use in indirect food contact applications.
What temperature range can glycol refrigeration handle?
With the correct concentration, glycol can protect systems down to -50°C. Most commercial systems operate between -5°C and -30°C.
What is glycol used for in refrigeration?
Glycol is used as a secondary coolant in refrigeration systems. It circulates through a closed loop to absorb and transfer heat from one area to another. This indirect method allows for precise temperature control, reduces the amount of refrigerant needed, and prevents freezing in cold environments.
How does a glycol cooling system work?
A glycol cooling system works by chilling a water-glycol mixture in a central chiller and then circulating it through insulated pipes to remote cooling areas. The fluid absorbs heat from the process or environment and returns to the chiller to be cooled again. This closed-loop setup supports long-distance cooling and consistent temperature control.
What is the purpose of the glycol system?
The purpose of a glycol system is to provide efficient, indirect cooling for processes or environments where direct refrigerant use isn't practical or safe. It helps prevent freezing, supports multi-zone cooling, and minimizes refrigerant charge and leakage risks in industrial and commercial refrigeration.
Is glycol the same as antifreeze?
Glycol is the primary ingredient in most antifreeze products, but they’re not exactly the same. Pure glycol must be mixed with water and often contains corrosion inhibitors to function as antifreeze. In refrigeration, food-grade glycol is used when safety and non-toxicity are required.
Can I mix glycol with antifreeze?
You should not mix different types of glycol (e.g., ethylene with propylene) or combine glycol with automotive antifreeze unless the products are chemically compatible. Doing so can reduce performance, cause corrosion, or damage system components. Always follow manufacturer guidelines for mixing.
Why does Bobcat use propylene glycol?
Bobcat uses propylene glycol because it is a safer, low-toxicity coolant with strong antifreeze properties. It protects equipment from freezing in low temperatures while minimizing health and environmental risks, especially in enclosed or operator-exposed environments where toxic coolants are not suitable.
