A glycol refrigeration system is an indirect cooling system that uses a water-glycol mixture as a secondary coolant to transfer heat away from industrial processes, HVAC systems, or food and beverage production lines. Unlike direct refrigerant systems, the refrigerant stays contained inside the central chiller — the glycol loop carries the cold energy outward to wherever it is needed.
The key advantage is simple: glycol mixed with water freezes at a much lower temperature than water alone, allowing the system to cool well below 0°C without the risk of freezing pipes or equipment. A 40% propylene glycol solution protects down to approximately −23°C; a 50% ethylene glycol solution protects to around −37°C.
This guide covers everything engineers and procurement teams need to know: how glycol refrigeration systems work, the difference between ethylene and propylene glycol, how to select the right concentration, which industries use these systems, and how to specify a glycol chiller from Geson.
How a Glycol Refrigeration System Works
A glycol refrigeration system operates as a closed loop with five main stages:
- Chilling: The central chiller cools the glycol-water mixture to the target setpoint temperature, typically between −15°C and +10°C depending on the application.
- Circulation: A pump drives the chilled glycol solution through insulated piping to the point of use — a fermentation tank, a process reactor, a cold room, or an HVAC air handler.
- Heat absorption: At the point of use, the glycol solution passes through a heat exchanger, absorbing heat from the process or space being cooled.
- Return: The now-warmer glycol solution flows back through return piping to the chiller.
- Re-cooling: The chiller removes the absorbed heat and returns the glycol to setpoint temperature, completing the cycle.
Because the system is sealed and closed-loop, glycol concentration remains stable, fluid losses are minimal, and contamination risk is low — a critical requirement for food, beverage, and pharmaceutical applications.
Ethylene Glycol vs Propylene Glycol: Which to Use
Two types of glycol are used in industrial refrigeration systems. Choosing the wrong type can create safety or regulatory problems, so it is important to match glycol type to the application from the start.
| Property | Ethylene Glycol (EG) | Propylene Glycol (PG) |
|---|---|---|
| Toxicity | Toxic — harmful if ingested | Non-toxic — FDA GRAS approved |
| Heat transfer efficiency | Higher | ~10–15% lower than EG |
| Viscosity at low temps | Lower — better flow | Higher — needs careful pump sizing |
| Freeze protection (50% mix) | Down to −37°C | Down to −33°C |
| Cost | Lower | Higher |
| Typical applications | Ice rinks, HVAC, industrial cooling, chemical plants | Breweries, food processing, pharma, dairy |
| Regulatory requirement | Not permitted where food contact risk exists | Required where food contact is possible |
| Disposal | Requires proper hazardous waste handling | Biodegradable, easier disposal |
Rule of thumb: Use propylene glycol for any application where the fluid could come into contact with food, beverages, potable water, or people. Use ethylene glycol for purely industrial applications — ice rinks, HVAC systems, chemical plants, data centers — where higher efficiency and lower cost matter more than food-grade safety.
Important: Never mix ethylene glycol and propylene glycol. Mixing different glycol types causes congealing, inhibitor breakdown, and filter blockages that damage the entire system.
Glycol Concentration and Freeze Protection Chart
The ratio of glycol to water determines the lowest temperature at which the solution remains liquid. Use this table to select the correct concentration for your application based on the coldest expected operating or ambient temperature.
| Glycol Concentration (%) | Ethylene Glycol — Freeze Point | Propylene Glycol — Freeze Point |
|---|---|---|
| 10% | −3°C (27°F) | −3°C (27°F) |
| 20% | −8°C (18°F) | −7°C (19°F) |
| 30% | −15°C (5°F) | −13°C (9°F) |
| 40% | −23°C (−9°F) | −21°C (−6°F) |
| 50% | −37°C (−35°F) | −33°C (−27°F) |
| 60% | −52°C (−62°F) | −51°C (−60°F) |
Design rule: Set your freeze protection level at least 5–8°C below the lowest expected operating temperature. For outdoor systems in cold climates, add a further safety margin for ambient temperature drops. Too much glycol reduces heat transfer efficiency and increases pumping energy costs — do not over-concentrate beyond what freeze protection requires.
Industrial Applications of Glycol Refrigeration
Glycol refrigeration systems are used wherever precise temperature control, freeze protection, or sub-zero cooling is required across extended piping distances or multiple cooling zones.
| Industry | Application | Glycol Type | Typical Temp Range |
|---|---|---|---|
| Brewing & beverage | Fermentation temperature control, crash cooling, wort chilling, beer line cooling | Propylene glycol | −5°C to +5°C |
| Food processing | Blast chilling, cold storage, process cooling | Propylene glycol | −10°C to +5°C |
| Dairy & wine | Milk cooling, wine fermentation temperature control | Propylene glycol | −5°C to +8°C |
| Pharmaceutical | Reactor cooling, clean room temperature control, API manufacturing | Propylene glycol | −15°C to +10°C |
| Ice rinks | Sub-floor refrigeration for ice surface maintenance | Ethylene glycol | −10°C to −5°C |
| HVAC & data centers | Building cooling, server room temperature control, freeze protection | Ethylene glycol | +5°C to +15°C |
| Chemical & plastics | Reactor cooling, injection mold cooling, extrusion cooling | Ethylene glycol | −15°C to +10°C |
| Printing & rubber | Process temperature control, equipment cooling | Ethylene glycol | +5°C to +20°C |
Key Components of a Glycol Refrigeration System
A complete glycol chiller system consists of the following components working together:
- Glycol chiller unit: The central refrigeration machine that cools the glycol solution to the setpoint temperature. Available in air-cooled and water-cooled configurations.
- Glycol reservoir/buffer tank: Stores the glycol solution and stabilizes system pressure. Larger tanks improve temperature stability and reduce chiller cycling.
- Circulation pump: Drives the glycol solution through the loop. Pump sizing must account for glycol viscosity at operating temperature, especially with propylene glycol at low temperatures.
- Insulated piping: Carries the glycol solution between the chiller and the points of use. Proper insulation is critical to prevent heat gain and condensation.
- Heat exchangers: Transfer cooling energy from the glycol loop to the process being cooled. Plate heat exchangers are common for high-efficiency close-approach applications.
- Expansion vessel: Accommodates changes in fluid volume as glycol expands and contracts with temperature changes.
- Control system: PLC-based controller manages chiller setpoint, pump operation, alarms, and remote monitoring. Geson chillers include LCD touchscreen controllers with RS-485/Ethernet connectivity.
Geson Glycol Chiller Systems
Geson has designed and manufactured glycol refrigeration systems for industrial and commercial customers since 2004. All Geson glycol chiller configurations are factory-tested before delivery and include full documentation of glycol charge weight, system pressure test records, and operating parameters.
Available glycol chiller configurations:
- Air-cooled scroll compressor chillers — 10TR to 100TR, suitable for propylene glycol systems in food and beverage applications, setpoint temperature −10°C to +25°C
- Water-cooled scroll compressor chillers — 10TR to 100TR, ideal for indoor installations with cooling tower
- Air-cooled screw compressor chillers — 50TR to 630TR, for large industrial glycol systems including ice rinks and chemical plants, setpoint −15°C to +10°C
- Water-cooled screw compressor chillers — 50TR to 1,500TR, for large-scale central glycol refrigeration systems
All Geson glycol chillers can be configured for ethylene or propylene glycol and include stainless steel evaporators where food-grade requirements apply. Lead time: 15 working days standard.
Contact Geson engineering team → Send your cooling load (TR or kW), glycol type, setpoint temperature, and ambient conditions for a formal quotation within 24 hours.
Glycol System Maintenance: What to Check
A properly maintained glycol system can operate reliably for 10–15 years. The most common causes of premature failure are glycol degradation, incorrect concentration, and inhibitor depletion. Follow this basic maintenance schedule:
- Every 3 months: Test glycol concentration with a refractometer. Verify freeze protection is still within the designed range. Top up with the same glycol type if concentration has dropped.
- Every 6 months: Test pH level of the glycol solution. Healthy glycol solution should be slightly alkaline, pH 8–10. pH below 7 indicates acid formation and glycol degradation — replace the fluid.
- Every 12 months: Inspect inhibitor levels. Inhibitors prevent corrosion of metal components; depleted inhibitors lead to pitting and system damage. Use inhibited glycol products and top up with inhibitor concentrate as needed.
- Every 2–3 years: Full glycol flush and replacement, or when pH, colour, or odour indicates significant degradation.
- Never: Mix different brands or types of glycol. Never use automotive antifreeze in food or HVAC glycol systems — it contains additives unsuitable for industrial use.
Frequently Asked Questions about Glycol Refrigeration
What is glycol refrigeration?
Glycol refrigeration is an indirect cooling method where a central chiller cools a water-glycol mixture, which is then pumped through insulated piping to cool processes, equipment, or spaces. The glycol prevents the solution from freezing at low operating temperatures, making it suitable for sub-zero applications. It is widely used in brewing, food processing, pharmaceuticals, ice rinks, and HVAC systems.
What is the difference between ethylene glycol and propylene glycol?
Ethylene glycol offers better heat transfer efficiency and lower viscosity, making it the preferred choice for purely industrial applications such as ice rinks, HVAC systems, and chemical plants. Propylene glycol is non-toxic and FDA-approved for food contact, making it mandatory for breweries, dairies, food processing, and pharmaceutical applications. The two types must never be mixed.
What concentration of glycol should I use?
The correct glycol concentration depends on the lowest temperature the system will reach during operation. As a general rule, your freeze protection level should be at least 5–8°C below your lowest expected operating temperature. A 30% solution protects to approximately −15°C; a 50% solution protects to approximately −37°C (ethylene) or −33°C (propylene). Avoid over-concentrating — excess glycol reduces heat transfer efficiency and increases pumping costs.
Can I use a standard water chiller as a glycol chiller?
Not directly. Glycol solutions are more viscous than water and have different heat transfer properties. A glycol chiller must be specifically designed with an evaporator sized for glycol-water mixtures, pumps rated for glycol viscosity at operating temperature, and materials compatible with the glycol type. Geson glycol chillers are factory-configured for the specified glycol concentration and temperature range.
What temperature can a glycol chiller reach?
This depends on the chiller design and glycol type. Standard Geson air-cooled scroll glycol chillers achieve setpoint temperatures of −10°C to +25°C. Screw compressor glycol chillers can reach −15°C to +10°C. For lower temperature applications down to −45°C, a low-temperature glycol chiller with a cascade or two-stage refrigeration system is required — contact Geson engineering for these specifications.
How long does glycol last in a refrigeration system?
With proper maintenance, inhibited glycol solution should last 2–5 years before requiring a full system flush and replacement. Key indicators that glycol needs replacing include: pH below 7.0, dark discolouration, strong odour, or visual contamination. Testing pH and concentration every 3–6 months is the most reliable way to extend glycol life and protect system components.
What is a glycol chiller used for in brewing?
In brewing, a glycol chiller circulates propylene glycol solution through jacketed fermentation tanks, conditioning tanks, and bright beer tanks to control temperature during fermentation and cold conditioning. The glycol never contacts the beer directly — it flows through the outer jacket of the tank, removing or adding heat as needed. Precise temperature control during fermentation is critical for yeast health and flavour development.
What is the difference between a glycol chiller and a water chiller?
A water chiller uses plain water as the secondary coolant and is limited to operating temperatures above 5°C to prevent freezing. A glycol chiller uses a water-glycol mixture that can operate at sub-zero temperatures without freezing. Glycol chillers are more expensive to operate due to the cost of glycol fluid, but are essential for any application requiring cooling below 5°C or freeze protection in cold environments.
Does Geson manufacture glycol chillers?
Yes. Geson has manufactured glycol chiller systems since 2004 for applications including brewing, food processing, pharmaceutical, ice rinks, and industrial process cooling. Systems are available from 10TR to 1,500TR in air-cooled and water-cooled configurations, for both ethylene and propylene glycol. Contact our engineering team with your cooling load and application details for a formal quotation.
What piping material should I use for a glycol system?
The most common piping choices are carbon steel (for ethylene glycol industrial systems), stainless steel (for propylene glycol food-grade systems), and copper (for smaller systems). Pre-insulated PEX (cross-linked polyethylene) pipe is popular for brewery and food processing glycol loops due to its ease of installation and chemical compatibility. Avoid galvanised steel and PVC — galvanised steel reacts with glycol inhibitors, and standard PVC is not rated for the temperature range of most glycol systems.
Related Resources
- Glycol Chiller vs Water Chiller: Which is Right for Your Application?
- Glycol Beer Chiller Systems for Breweries
- Brewery Glycol Chiller Systems
- Air-Cooled Scroll Chillers — 10TR to 100TR
- Air-Cooled Screw Chillers — 50TR to 630TR
- Contact Geson Engineering Team