How to Mix Coolant for Industrial and HVAC Systems the Right Way

Heating and cooling systems in commercial buildings depend on properly prepared coolant to maintain reliable operation throughout the year. Whether protecting a closed loop HVAC system during harsh Northeastern winters or maintaining consistent heat transfer in year-round applications, understanding how to mix coolant correctly helps reduce the risk of freezing, corrosion, equipment damage, and unnecessary maintenance. The right coolant mixture also supports efficient system performance by balancing freeze protection with effective thermal transfer.

Unlike a car’s cooling system, industrial and HVAC applications require a more controlled approach to coolant preparation. Factors such as the type of concentrated coolant, the quality of the water, the desired ratio, and the operating conditions all influence the final mixture. This guide explains the fundamentals of how to mix coolant for commercial systems, outlines common mistakes to avoid, and highlights best practices that help facility managers and maintenance professionals protect their equipment over the long term.

Key Takeaways

• Properly mix coolant using the manufacturer’s recommended ratio to provide reliable freeze protection while maintaining efficient cooling system performance.
• Use high-quality distilled water or appropriately treated water whenever specified to help reduce corrosion, mineral deposits, and scaling.
• Regularly test coolant concentration and inhibitor levels, especially before winter or after adding make-up water to the system.
• Avoid mixing different types of coolant unless compatibility has been verified, as improper combinations can reduce protection and affect performance.
• Routine monitoring and maintenance help extend equipment life, improve operational reliability, and support long-term control of closed loop HVAC systems.

What Is Industrial Coolant?

Industrial coolant is a specialized fluid used to transfer heat while protecting closed loop HVAC and process cooling systems from freezing, corrosion, and scale formation. Rather than simply regulating temperature, coolant helps maintain system reliability by preserving the condition of pipes, pumps, coils, and other critical components. In commercial facilities, the coolant type and concentration are selected based on the operating environment, equipment requirements, and desired level of freeze protection.

Many industrial systems use glycol-based antifreeze formulations because they provide dependable protection in climates with significant seasonal temperature changes. Unlike plain water, glycol solutions remain effective at lower temperatures while also carrying corrosion inhibitors that help safeguard metal surfaces throughout the system.

Types of Industrial Coolants

The two most common different types of industrial coolant used in HVAC and closed loop applications are ethylene glycol and propylene glycol.

• Ethylene glycol offers excellent thermal performance and is commonly used in industrial applications where there is no potential for contact with potable water or food processing systems.
• Propylene glycol is widely used in commercial buildings, schools, healthcare facilities, and other occupied environments because of its lower toxicity while still providing reliable freeze protection and corrosion resistance.

Most glycol products are sold as a concentrated coolant, or concentrate, that must be diluted with the appropriate amount of water before use. The proper dilution helps balance freeze protection, pumping efficiency, and heat transfer, making the final mixture suitable for the intended application.

How to Mix Coolant Correctly

Preparing the proper coolant solution involves more than simply combining glycol and water. The correct mixture depends on the level of freeze protection required, the manufacturer’s recommendations, and the operating conditions of the system. Following a consistent process helps ensure the coolant delivers effective thermal performance while minimizing the risk of corrosion, freezing, and premature equipment wear.

1. Determine the Required Freeze Protection

Before preparing the solution, identify the lowest temperature the cooling system is expected to encounter. Facilities in colder climates generally require a higher glycol concentration than those operating in milder conditions. Always start by reviewing the equipment manufacturer’s documentation and the specific requirements of the application before deciding on a mixing ratio.

2. Select the Appropriate Concentrated Coolant

Choose a concentrated coolant formulated for industrial or HVAC use rather than products intended for automotive applications. The selected type should match the system’s materials, operating temperatures, and maintenance program. Using the appropriate glycol formulation helps protect equipment while maintaining long-term performance.

3. Use High-Quality Water

Water quality is just as important as the coolant itself. Most manufacturers recommend using distilled water, deionized water, or appropriately treated water to reduce the introduction of minerals that can contribute to scale and corrosion. Poor water quality can reduce inhibitor effectiveness and negatively affect overall performance, even when the glycol concentration is correct.

4. Measure the Correct Mixing Ratio

Carefully measure both the glycol concentrate and water before combining them. Many industrial systems use a 50/50, or half glycol and half water, mixture, although the exact ratio depends on the desired level of freeze protection and the manufacturer’s specifications.

The table below provides a general example of commonly used glycol concentrations.

These values are general guidance. Always follow the coolant supplier’s recommendations and the equipment manufacturer’s specifications for the final concentration.

5. Mix and Fill the System

After measuring the required quantities, thoroughly mix coolant with water before introducing it into the system, whenever practical. For larger installations, the solution may be blended in a dedicated mixing tank before being pumped into the loop. Slowly pour the prepared coolant into the designated fill connection while monitoring the system level to avoid introducing excess air.

6. Test the Finished Solution

Once circulation has stabilized, test the coolant concentration using the appropriate field instrument, such as a refractometer. Verifying the final concentration confirms that the intended ratio has been achieved and provides an opportunity to identify adjustments before seasonal operation begins. Periodic testing should also become part of the facility’s routine maintenance program, particularly before winter, after adding make-up water, or following significant system repairs.

Benefits of Properly Mixed Coolant

Using the correct coolant concentration does more than prevent freezing. A properly prepared solution helps maintain efficient operation, protects valuable equipment, and supports the long-term reliability of closed loop HVAC systems. Even a small deviation from the recommended mixing ratio can affect system performance, making routine verification an important part of preventive maintenance.

Freeze Protection

One of the primary reasons for using glycol antifreeze is to reduce the risk of freezing during cold weather. If the coolant concentration is too low, the liquid may not provide adequate protection, increasing the possibility of frozen pipes, damaged coils, and costly repairs. On the other hand, using a concentration that is higher than necessary can reduce heat transfer efficiency and increase the energy required to circulate the fluid.

Corrosion Control

Modern industrial coolants contain corrosion inhibitors that help protect metal surfaces throughout the system. These additives reduce the likelihood of rust, pitting, and other forms of corrosion that can shorten equipment life and increase maintenance costs. However, inhibitor effectiveness depends on maintaining the proper coolant concentration and water chemistry. Regular testing helps verify that the coolant continues to provide the intended level of protection.

Heat Transfer and System Performance

The primary function of a coolant is to transfer heat efficiently throughout the cooling system. A properly balanced mixture allows the fluid to absorb and release heat while maintaining stable operating temperatures. Incorrect mixing can reduce the coolant’s thermal transfer ability, forcing pumps and heat exchange equipment to work harder and potentially increasing operating costs.

Common Coolant Mixing Mistakes to Avoid

Even when using a high-quality coolant, improper preparation or maintenance can reduce its effectiveness and shorten equipment life. Avoiding the following mistakes helps maintain reliable operation and supports the long-term health of industrial and HVAC systems.

• Guessing the mixing ratio instead of measuring accurately. Estimating the amount of glycol and water can result in an incorrect concentration. Always measure each component and prepare the recommended mixture to achieve the desired level of freeze protection.
• Using untreated water. Filling the system with untreated water may introduce minerals and contaminants that contribute to scale formation and corrosion. Using distilled water or appropriately treated water helps preserve coolant quality and improve overall system performance.
• Mixing incompatible coolant formulations. Not all coolant products are chemically compatible. Combining different types of coolant without confirming compatibility can reduce inhibitor effectiveness, create deposits, or shorten coolant service life. Always verify compatibility before adding a new product to an existing system.
• Skipping routine testing and maintenance. Coolant condition changes over time as inhibitors are consumed and make-up water is added. Facilities should test coolant concentration and water chemistry regularly instead of waiting for operational problems to appear.
• Applying automotive maintenance practices to HVAC systems. Procedures such as performing a radiator flush or replacing old coolant on a fixed schedule are common for automotive applications but do not always apply to commercial closed loop systems. Industrial maintenance should instead be based on water analysis, inhibitor levels, and system performance. When replacement is necessary, properly drain the existing coolant and follow the manufacturer’s recommendations before refilling the system.

How Often Should Industrial Coolant Be Tested?

Routine testing helps confirm that the coolant continues to provide adequate freeze protection, corrosion control, and heat transfer. Rather than relying solely on time-based maintenance, facilities should evaluate coolant condition as part of a comprehensive water treatment program.

As a general best practice, coolant should be tested:

• Before the start of winter
• After adding significant amounts of make-up water
• Following major system repairs or modifications
• Whenever contamination is suspected
• As part of scheduled preventive maintenance

Regular monitoring allows facility teams to identify changes in coolant concentration or water chemistry before they affect equipment reliability. This proactive approach helps maintain consistent performance while reducing the likelihood of unexpected downtime and costly repairs.

Professional Glycol Management for Industrial and HVAC Systems

ClearWater Industries supports commercial and industrial facilities with customized programs designed to protect closed loop and glycol systems through every stage of operation. Depending on the application’s needs, services may include:

• Closed Loop Water Treatment Programs that incorporate custom treatment design, corrosion inhibitor programs, glycol concentration measurement, water quality testing, leak detection, and ongoing performance monitoring.
• Glycol System Services including glycol addition and mixing, concentration verification, laboratory analysis, system charging studies, filtration support, and heat transfer optimization for HVAC and industrial applications.
• Commercial Water Testing to evaluate glycol concentration, corrosion rates, water chemistry, and other system conditions that may affect long-term reliability and efficiency.
• Water Treatment Consulting Services that provide professional system evaluations, treatment program optimization, compliance guidance, and practical recommendations to improve equipment performance while reducing operating costs.
• Ongoing Monitoring and Maintenance through scheduled inspections, operator training, performance trending, troubleshooting, and emergency support to help facilities maintain reliable operation throughout the year.

Whether commissioning a new glycol system or maintaining an existing closed loop network, professional monitoring can help identify developing issues before they lead to equipment damage or operational disruptions. Contact ClearWater Industries to learn how their services can help optimize coolant performance, improve equipment reliability, and support long-term operational efficiency.

Frequently Asked Questions