Most Hydronic Heating Systems Use Water, So What is Glycol Used for in HVAC?
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There are many propylene glycol uses in the world, but is it necessary to add glycol to water in hydronic heating systems? What about adding glycol for cooling systems? This article explains why adding glycol to water provides important protections.
Water is the Basic Fluid used in Hydronic Heating and Cooling Systems
Many building heating and cooling systems use water to move temperatures around the building. The water is heated or cooled, and pumps transport the water to the various coils where air takes the heat or cooling into the space.
To maintain good indoor air quality, fresh air must be brought into the building while some air is exhausted. The air is pulled in by fans located in air handling units and is the same temperature as the outdoor air. In northern climates, the incoming air temperature can be very cold. Care is exercised during the design to assure that the ice-cold air does not freeze the water but things can go wrong.
Three Example Systems Where Adding Glycol Can Save the Day
Example #1: Air Handling Unit Freeze Protection
Look at the photo above. This heating coil uses a two-way control valve with the main heating pumps operating on variable speed drives. This will save energy and operating costs.
The downside of the system is the concern about stopping the flow through the coil where cold air is rushing in. Engineers use a piping practice named primary-secondary to assure there is always flow across the coils. The primary-secondary piping depends on a small circulator pump to move the water around.
If the circulator pump fails, the flow may stop, and cold air could freeze the water and damage the coils. Many engineers will use a percentage propylene glycol antifreeze mixed with the water to avoid catastrophic coil damage.
Example #2: Glycol Chillers not used in the Winter
Many HVAC systems have air cooled chillers used throughout the summer. In the winter they are drained so they do not freeze. This provides two problems for owners.
What happens when we get a hot spell in the fall. The people in the building are hot and they do not blame the system, they blame the operations people. Adding glycol to cooling systems will allow the use in both summer and winter.
The second problem occurs when the cooling system is started. Many owners simply open the valves to the air cooled chiller and allow the system and the makeup water to fill the pipe. This causes a large amount of air to be introduced into the system. This air will cause cooling problems for weeks or even months.
When people ask, what is a glycol chiller? The answer could simply be a chiller that can run all year if needed. Remember that not any old antifreeze will do. The glycol used in chilled water systems should be the right percentage and have the right mix of inhibitors. Try our glycol concentration calculator to determine the required concentration for your application or contact us today for help finding the correct solution for your application.
Example #3: Pipe in Unheated Spaces
We showed above the glycol chiller can be used all year round. There is another concern with piping systems where there is no flow at times. Often these pipes may run through unheated spaces or spaces with cold outside air blowing across the pipe.
Sometimes the design included heat in a space to protect the chilled water or heating system. During the life of the building the space becomes unused. To save money, the owner may turn the heat down or even off. Water may freeze but a glycol antifreeze system will protect the pipe.
Additional Advantage of Glycol in Closed Hydronic Heating and Cooling Systems
Not all glycols are the same. The Dowfrost® and Dowtherm® products supplied by Go Glycol Pros include an inhibitor package which protects the pipe much better than water or even water with chemicals added. Click here to learn more about the benefits of inhibited heat transfer fluid.
Adding the proper type, concentration (or mix), and brand of glycol to closed heating and cooling systems will offer protection. Glycols and antifreeze should not be added to systems without an understanding of the effects on pumps and heat or cool output. For assistance in getting started, contact our customer service team today!
Are you interested in learning more about Glycol Temperature? Contact us today to secure an expert consultation!
MEET THE PRO: NORM HALL
Norm graduated from Wayne State University in Electrical Engineering. Over the past 40 years at RLD Norm has worked on design/engineering of systems, estimating, outside sales & management. Norm enjoys golf, playing with his grandkids, teaching eighth grade catechism classes, and volunteering at local food banks.
Go Glycol Pros is a distributor of DOW® heat transfer fluid for over 20 years. We sell glycol online with no accounts or order minimums required. Available in 275 gallon tote, 55 gallon drum or 5 gallon pail, high purity DOW antifreeze is premixed with deionized water (DI water) at our in-house facility and ships out within just one business day. Our inhibited glycols include: DOWFROST HD propylene glycol, DOWFROST food grade propylene glycol and DOWTHERM SR-1 ethylene glycol.
Explore more helpful tips and advice at goglycolpros.com. Our knowledgeable glycol experts are ready to help you with your latest hydronic HVAC project.
View Dow Ethylene Glycol, Propylene Glycol and Food Grade Propylene Glycol
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Disclaimer: Go Glycol Pros and it&#;s affiliates can not be held liable for issues caused by use of the information on this page. While the- information comes from many years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions that result from this information. Please feel free to contact us if you do have any questions.
Glycol is a very important element in any cooling system. Despite its ubiquity and its importance, most customers don&#;t fully understand all that it does. In an effort to clear up some of the confusion about glycol, here are our answers to the most commonly asked questions.
Glycol is a water-miscible organic compound in the alcohol family. It is commonly used for cooling in industrial and mechanical applications. Glycol is sometimes called antifreeze or a coolant. Though it acts similarly to a refrigerant, and someone may refer to glycol as a refrigerant, this statement is incorrect. Glycol cools solely through heat transfer in an exchanger; whereas, refrigerant uses an evaporation-condensation cycle to remove heat.
The most important role glycol plays in a process cooling system is to adjust the temperature range of the system. Without any glycol in the system, the water will freeze at the normal 32°F (0°C). In this case, the system ambient temperature can never go below this temperature. However, many systems need temperature flexibility as pipes travel outside and into unheated areas. Adding glycol to the water lowers the freezing point. The percent of glycol determines what the new freezing point will be.
A lower freezing point means process fluid can be kept at colder temperatures. A greater difference between medium temperatures allows for a faster heat transfer process. Heat always travels in the direction of higher temperature to lower temperature. When a coolant with a colder temperature is used, more of the energy can be transferred from the other fluid or process to the coolant.
Glycol often contains corrosion inhibitors which can help to prolong the life of components. Its main function is to enable a cooling system to operate at temperatures below the freezing point of water. Certain systems may require this lowered cooling for optimum performance.
Deciding on the perfect glycol-water mixture is critical to your chiller&#;s operation. You will need to consider factors such as ambient temperature, desired lowered temperature, and heat transfer rate. The best way to determine a percentage for your system is to talk to a Chase Cooling Systems Expert. As there can be adverse effects on the cooling system when using glycol, the glycol concentration should be limited only to what is required for freeze protection.
Yes. There are two types of glycol commonly used for process chillers: Propylene and Ethylene Glycol. These products vary on metrics such as performance, environmental factors, and general safety. The specific needs of your process will determine which glycol type is best for your system.
In general, propylene glycol is considered food grade and can be used in food and beverage operations. Most brewery applications use this type of glycol. Additional certifications such as United States Pharmacopeia (USP) stamp can be sought to ensure that any glycol in the mixture indeed is safe for consumers.
Glycol can be purchased from reputable vendors, including Chase Cooling Systems. When purchasing glycol, know the concentration you need and the concentration you are purchasing. Glycol comes in stock concentrates as well as in set blends. It can be ordered in 55 gal drums, 5 gal pails, or bulk 275 gal totes. Always make sure you are purchasing the appropriate grade glycol. Automotive anti-freeze should never be used in a chiller.
If you have purchased a ratio that is higher than what your system needs, do not panic. You can still use this blend. However, you will need to perform onsite mixing. This process will involve adding water to the blend. Only use filtered, distilled or reverse-osmosis water. General tap water often has minerals such as calcium that can affect the chiller. After mixing and filling the system, any air pockets will need to be removed to prevent system frothing in the chiller.
Copper or ABS piping remain industrial standards for system piping. PVC is also sometimes used. The most important thing to consider when setting up a new system, is that the piping is properly sized. An undersized pipe may accidentally increase the pressure and could risk the rest of the system. Whereas, an oversized pipe may lower overall efficiency. Glycol is not recommended with galvanized piping, as it may adversely react with Zinc.
Since many chillers are factory set for water only solutions, some minor adjustments may need to be made. Areas such as the evaporator, pump, and hot gas bypass valve may need adjustments. Glycol has a lower specific heat capacity and a lower heat transfer efficiency. These factors must be considering when designing for a particular system. A trained professional should be able to easily make the necessary changes. The addition of glycol also changes maintenance concerns, as the new element will need to be tested and maintained along with the mechanical elements of the machine.
If your system or atmosphere have the potential to go below 32°F (0°C), then a glycol-water mixture should be used. A chiller&#;s process fluid should never freeze, as this stops the chiller&#;s ability to do work, and could even cause mechanical damage. To prevent these problems, talk to an expert and discover the best glycol mixture for your system.
If you are looking for more details, kindly visit Glycol to Water Ratio in Chiller.