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What is Free Cooling?

Free cooling is an economical method of using low external air temperatures to assist in chilling water, which may then be used for industrial processes or air conditioning systems. When outdoor temperatures are lower than chilled water temperatures, the system utilizes the cool outdoor air as a freecooling source. To build this type of unit we take a cooling only chiller, add two water coils, 3-way valve, solenoid valves, multiple condenser sections, inverter fans and free cooling software in order to provide a integrated free cooling chiller option. Read about our compact free cooling unit here. The NYB.

How Does it Work?

When the ambient temperature drops 4°F below return water temperature, the 3-way valve will divert all return water to free cooling coils. This is hybrid free cooling where a portion of the cooling is done by free cooling coil, the rest by mechanical cooling. What’s unique in this type of free cooling is the fan speed to is set to maximum or 100% even in hybrid mode, where most systems limit their fan speed in order to control refrigerant head pressure.

How is it possible to operate at 100% fan speed without going off on low head pressure? Rather than controlling the head pressure with fan speed,control the head pressure by isolating sections of the condenser coil which will keep the head pressure where it needs to be at any temperature. Provide the condenser coils with solenoid valves which allows  shutting off sections of the condenser. When ambient temperature is approximately 18°F below chilled water setpoint, all the compressors are off and the unit operating in total free cooling mode.

Why Free Cooling?

For any application where ambient temperature falls 20°F below supply water temperature, free cooling makes sense from an economic perspective. Instead of compressors doing work to get cooling, waterside economizer can provide the same cooling, hence the term “free cooling.”

We have free cooling calculator which we can run for for a city to show exactly the savings in operating cost between a standard chiller and free cooling chiller. With each compressor shut-off during hybrid mode, EER goes a step higher. Another bonus, which won’t be shown in any cost calculator is extended life of compressor in a free cooling chiller because they will run less hours per year compared to a standard chiller. You can save up to 30% more energy with our integrated free cooling chiller, compared to a standard chiller. Use our Free Cooling Calculator to calculate potential savings attributable to the use of free cooling. 

Other Systems

1. Chiller Dry Cooler
With this setup, the chiller works to meet 100% of the load. Only when the ambient is low-enough for dry cooler to meet 100% of the load will the chiller go off and dry cooler turn on. Disadvantage of this system is you don’t benefit from the energy savings of the hybrid free cooling mode. Another disadvantage is added footprint of installing 2 sets of equipment

2. Competitors Free Cooling Chiller
Some competitors have their free cooling as a chiller + dry cooler module beside each other which works identical to option one. Some others have water coils as an accessory installed outside DX coil. The disadvantage of this setup is they either don’t have hybrid mode, or if they do, it is with fan speed lowered which eliminates most of the savings of hybrid mode. Another competitor has recently introduced their free cooling chiller and has scarce information, but based on limited available data, it doesn’t appear to low ambient like ours, not does it appear to have hybrid mode like ours.

With Aermec, we can also offer modular solutions where all modules or some modules are free cooling. With NYB, we have the world’s only AHRI certified integrated free cooling scroll chiller.


Applications for free cooling

  • Any server room that requires cooling 24/7/365
  • Marijuana dispensary for dehumidification
  • Manufacturing process application
  • Hotel or hospital that have year-round cooling load

In any of these setups, it is extremely crucial to have a reliable system whose operating costs are as low as possible. The application and savings that come with our free cooling systems can provide massive value for these applications. Access our Case Studies here.