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Glycol Feed System for Chiller Condenser Water Loop

Glycol Feed System for Chiller Condenser Water LoopGlycol is like antifreeze and is used in chilled water piping loops to prevent freezing. Everyone knows when the pipes freeze they also break and start leaking. Having antifreeze in a chilled water loop is important to prevent freezing. So, how do you keep antifreeze in the loop when the water/glycol mix goes out to the cooling tower and there is a loss of water/glycol through windage or drift? Meet the glycol make-up unit where it can automatically be added to the loop and prevent freezing. Antifreeze make-up units range from automatic units that will inject the antifreeze right into the loop to manual units that require an operator to control the process of adding antifreeze to the water loop. These make-up units make it easy to add it to the loop without having a shut-down of the chilled water loop it serves so the loop can continue to run while the glycol is injected directly into the loop. The loops are designed to work at low ambient temperatures need the water/glycol mix to prevent freezing especially for critical facilities like data centers that need to remain operation no matter what the outside temperature conditions are. Percent of antifreeze to water depends on the expected operational temperatures outside so the mix is important for expected operating temperatures. An example of this is listed in the following table (follow equipment manufactures instructions for the recommended mix of antifreeze to water for temperatures):. Each loop requires a different ratio of mix based on ambient conditions, flow rates and other factors for determining the proper mix ratios.

Glycol Feed System for Chiller Condenser Water Loop | Antifreeze Protection - Percentage Water to Temperature Ratio

Propylene Glycol% to Water

  • 10% – 26°F
  • 20% – 18°F
  • 30% – 8°F
  • 40% – -7°F
  • 50% – -29°F

Additionally, it is important to use the right kind of antifreeze specifically for these systems. Some types of antifreeze are extremely harmful to the environment including certain types of propylene glycol. Food grade propylene glycol is available and should be used to avoid issues with environmental agencies.

glycol injection for chilled water plantAntifreeze is especially necessary for condenser water and cooling towers when the cooling tower is used in the winter time as a waterside economizer. The antifreeze prevents the water from freezing in extremely cold weather while allowing the water to be chilled naturally. This naturally chilled water using the cold outside air temperatures saves from running the chiller to chill the water.

One can see the huge benefit and cost savings from using the outside cold air to provide chilled water rather than using the chillers. Savings in electrical use along with savings in maintenance from reduced run time on the chillers translate into true savings for the user. I am certain someone is asking why you need chilled water in the winter time when heating is needed to heat instead of cool? In this case, the building is a data center and heat load is constant from winter to summer as the servers in the data center are constantly producing heat. In this case and case for that matter, it is essential that the water is protected from freezing so an antifreeze solution or mix with the water is necessary to prevent freezing.

A data center is considered a critical facility so it is a given that antifreeze be used for this purpose to prevent the water from freezing in the pipes or the cooling tower. Other applications which require cooling in the winter thereby requiring the cooling tower to be used whether it is used in a water side economizer or to cool the condenser water from the chiller include industrial applications and some commercial applications where chilled water cooling is needed in the winter. One of the problems that must be overcome in the design of a chilled water system that utilizes antifreeze is derating the coil or heat exchanger depending on the amount of antifreeze used in the system to prevent the condenser water or water side economizing water from freezing.

Glycol Feed System for Chiller Condenser Water Loop – The heat transfer rate from water is different than the heat transfer rate from a water/antifreeze mix thereby requiring the chilled water coil or the heat exchanger to be derated for the system with antifreeze. A good rule of thumb for the derating is approximately 5 to 10 percent. Additionally, pump capacity for pumping the glycol/water mix will change. The capacity for the pump will not be the same as with straight water as the solution of glycol/water mix is more dense than straight water so all these matters must be addressed by an engineer before antifreeze can be added to the system.

Glycol Feed System for Chiller Condenser Water Loop

Before making changes to any HVAC system one should consult a mechanical engineer familiar with the particular system in question including an antifreeze feed system for a chiller condenser water loop.

To learn more about HVAC and chilled water systems click here.

High Performance HVAC

Glycol Feed System for Chiller Condenser Water Loop