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 freeze protection: adding the correct inhibited glycol product lowers the solution’s freezing point and can support sub-zero process temperatures or protect outdoor piping during cold weather. The required concentration must be selected from the current data for the exact fluid product, because freeze point, burst protection, viscosity and heat-transfer performance vary by formulation.
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.
Need a glycol chiller selection? Send the process heat load or required capacity, supply and return fluid temperatures, glycol product and concentration, flow rate, minimum and maximum ambient temperatures, application and power supply. Geson engineering will review the complete duty before recommending equipment.
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 project setpoint. The achievable leaving-fluid temperature depends on the refrigeration design, glycol formulation, concentration and operating conditions.
- 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.
In a correctly commissioned closed loop, fluid loss and contamination can be limited, but concentration and fluid condition still require periodic testing. Air ingress, make-up water, leaks, process contamination and excessive temperature exposure can change the chemistry over time.
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 | Lower acute toxicity than EG; suitability depends on the complete inhibited fluid product and its approvals |
| Heat transfer efficiency | Higher | Generally lower than EG at comparable conditions; verify with supplier properties |
| Viscosity at low temps | Lower — better flow | Higher — needs careful pump sizing |
| Freeze protection (50% mix) | Depends on concentration and the specific product formulation | |
| Cost | Lower | Higher |
| Typical applications | Ice rinks, HVAC, industrial cooling, chemical plants | Breweries, food processing, pharma, dairy |
| Regulatory requirement | Selection is restricted where ingestion or contamination risk exists | Often selected where lower toxicity or documented food-related suitability is required |
| Disposal | Follow the fluid supplier’s safety data sheet and local disposal requirements | |
Selection principle: EG is commonly considered where thermal performance and low-temperature pumping efficiency are priorities and exposure risk is tightly controlled. PG is often considered where lower toxicity is required. The final choice must account for local regulations, contamination risk, materials, operating temperature and the approvals of the complete inhibited heat-transfer fluid—not the base glycol alone.
Compatibility note: Do not mix unspecified glycol products, brands or inhibitor packages without written compatibility guidance from the fluid manufacturer. If the existing fluid is unknown, sample and identify it before topping up or converting the system.
Glycol Concentration and Freeze Protection Chart
The ratio of glycol to water affects freeze point, burst protection, viscosity, heat capacity, pressure drop and pump power. The values below are a preliminary comparison only; they are not a substitute for the current concentration chart published for the exact inhibited glycol product used on the project.
| 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) |
Engineering rule: Establish whether the project needs freeze protection during operation, burst protection during shutdown, or both. Then select a concentration and safety margin using the fluid manufacturer’s current data. Excess concentration can reduce heat-transfer performance and increase viscosity, pressure drop and pumping energy, especially at low temperature.
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 | Common Fluid Approach | Design Note |
|---|---|---|---|
| Brewing & beverage | Fermentation temperature control, crash cooling, wort chilling, beer line cooling | PG is often considered; confirm the complete fluid’s approvals | Size for peak fermentation and pull-down loads |
| Food processing | Blast chilling, cold storage, process cooling | Selected according to contamination risk and local requirements | Separate the process where hygienic isolation is required |
| Dairy & wine | Milk cooling, wine fermentation temperature control | PG is often considered for lower-toxicity duties | Use actual milk, tank or fermentation cooling load |
| Pharmaceutical | Reactor cooling, clean room temperature control, API manufacturing | Project-specific qualified heat-transfer fluid | Confirm material, cleaning and regulatory requirements |
| Ice rinks | Sub-floor refrigeration for ice surface maintenance | EG or another engineered secondary coolant | Account for slab, brine-loop and pull-down conditions |
| HVAC & data centers | Building cooling, server room temperature control, freeze protection | EG or PG according to exposure risk and site policy | Check winter protection, redundancy and pumping energy |
| Chemical & plastics | Reactor cooling, injection mold cooling, extrusion cooling | Selected for process temperature and exposure risk | Use measured or calculated process heat load |
| Printing & rubber | Process temperature control, equipment cooling | Selected for materials and operating conditions | Confirm fluid compatibility with equipment and seals |
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: The control package may manage chiller staging, fluid temperature, pumps, alarms and remote interfaces. Required communications and integration points should be stated in the enquiry and confirmed in the quotation.
Geson Glycol Chiller Systems
Geson supplies engineered glycol chiller systems for industrial and commercial process cooling. Equipment selection is based on the actual fluid, concentration, leaving and return temperatures, flow rate, ambient conditions, site utilities and required redundancy.
Relevant equipment configurations include:
- Air-cooled scroll chillers for packaged and modular process duties
- Water-cooled scroll chillers where a cooling-water system is available
- Air-cooled screw chillers for larger outdoor process loads
- Water-cooled screw chillers for larger central systems
Materials, evaporator design, compressor configuration, controls and documentation are confirmed against the specified duty. Do not assume that a standard water-chiller selection will deliver its nominal water capacity when operated with glycol.
Contact Geson engineering team → Send the cooling load, fluid product and concentration, supply and return temperatures, flow rate, ambient range, power supply and application details for a project-specific selection.
Glycol System Maintenance: What to Check
Glycol-loop reliability depends on fluid chemistry, operating temperature, oxygen ingress, contamination, make-up water and maintenance. Use the heat-transfer-fluid supplier’s test limits and the equipment manufacturer’s maintenance requirements rather than a universal replacement interval.
- At commissioning: Record the exact product, batch, concentration, water quality, refractometer reading and laboratory baseline.
- During routine inspection: Check fluid level, leaks, concentration, appearance, strainers, pump condition, temperatures, pressure drop and evidence of corrosion.
- At the supplier’s recommended interval: Test pH, reserve alkalinity and inhibitor condition using limits for the specific product.
- Before topping up: Identify the existing fluid and confirm product compatibility. Adding water or a different formulation can alter protection and corrosion control.
- When results fall outside limits: Consult the fluid supplier before adding inhibitor, partially replacing fluid or performing a complete clean and refill.
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 generally offers lower viscosity and better heat-transfer performance at comparable conditions, but it has greater toxicity concerns. Propylene glycol is often considered where lower toxicity is required. The complete inhibited fluid—not the base glycol alone—must meet the project’s safety, regulatory and material-compatibility requirements. Do not mix unspecified products without written compatibility guidance.
What concentration of glycol should I use?
The concentration depends on the specific inhibited product, required freeze or burst protection, minimum operating and shutdown temperatures, materials and hydraulic design. Select it from the current supplier chart and include an appropriate project safety margin. Avoid unnecessary over-concentration because viscosity, pressure drop and pumping energy can increase while heat-transfer performance falls.
Can I use a standard water chiller as a glycol chiller?
Only after the manufacturer verifies the duty. Glycol changes heat capacity, heat-transfer coefficient, viscosity, pressure drop and pump requirements. The evaporator, flow limits, pump, controls and materials must be checked for the exact fluid, concentration and temperature.
What temperature can a glycol chiller reach?
It depends on refrigeration design, compressor operating envelope, evaporator approach, glycol product and concentration, flow rate, ambient or condenser-water conditions and required capacity. State the required supply and return fluid temperatures in the enquiry; the achievable duty must be confirmed in the equipment selection.
How long does glycol last in a refrigeration system?
There is no universal replacement interval. Fluid life depends on product chemistry, temperature exposure, oxygen ingress, contamination, water quality and maintenance. Establish a commissioning baseline and test concentration, pH and inhibitor condition against the specific supplier’s limits; use laboratory analysis when condition is uncertain.
What is a glycol chiller used for in brewing?
In brewing, a glycol loop can circulate through jacketed fermentation, conditioning and bright-beer tanks to remove heat during fermentation and cold conditioning. The process and secondary fluid should remain isolated by the equipment boundary. Fluid selection and any required approvals depend on the installation’s contamination risk and local requirements.
What is the difference between a glycol chiller and a water chiller?
A water loop offers better heat-transfer and pumping performance where freeze protection is unnecessary. A glycol loop lowers the freezing point for sub-zero duties or cold-weather protection, but it also changes heat capacity, viscosity, pressure drop and equipment capacity. The choice should be based on operating and shutdown conditions, not a universal temperature threshold.
Does Geson manufacture glycol chillers?
Yes. Geson supplies air-cooled and water-cooled glycol chiller systems for industrial and commercial process cooling. Final configuration and capacity are selected from the actual fluid product, concentration, temperatures, flow, ambient conditions, utilities and application requirements.
What piping material should I use for a glycol system?
Piping material must be selected for the exact inhibited fluid, concentration, temperature, pressure, oxygen exposure, joining method and applicable code. Carbon steel, stainless steel, copper and compatible polymer systems may be used in appropriate designs. Confirm compatibility with the fluid and piping manufacturers; do not infer piping suitability from EG versus PG alone.