How to Prevent Freezing in Outdoor Chillers

In areas with cold winters, Outdoor chillers are prone to freezing during winter. Frozen chillers can lead to costly repairs and prolonged downtime. Why do chillers freeze? How to prevent freezing?

Why do outdoor chillers freeze or crack?

---

Outdoor chillers are designed with multiple antifreeze measures, such as selecting components made of low-temperature resistant materials, built-in automatic cycle antifreeze programs, and heating and insulation devices. Why do chillers still freeze despite this? It may be due to the following reasons.

The ambient temperature is too low

Outdoor chillers are exposed to the natural environment for a long time. When the local winter temperature is below 0℃, the standing chilled water in the system may freeze. Especially at night, the temperature is lower at night, and the equipment may be in standby or low load state, and the liquid flow rate in the system is very slow. In this case, the heat in the system will be lost quickly, resulting in freezing.
 
In addition, although the chiller itself adopts an antifreeze design, it also needs additional insulation, such as covering with thermal insulation blanket. Because the exposed pipes will lose heat quickly. In North America, Northern Europe, Russia and other regions, the winter is long and cold. If the insulation is not done well, the low-temperature outdoor chiller is also likely to freeze.

Incorrect coolant concentration

The coolant used in the chiller is generally water, glycol-water mixture or thermal oil. Among them, glycol-water mixture has a high cost-effectiveness, so it is common in low-temperature chillers. However, if the solution ratio is improper, its freezing point will be higher than the lowest ambient temperature.
 
For example, when the concentration of glycol is 10%~20%, the freezing point is -3℃~-8℃. If the local winter temperature is -15℃, this equipment cannot effectively prevent freezing even with good insulation measures. Some users use pure water to save costs, but its freezing point is 0℃, which is very easy to freeze in winter. In addition to improper ratio, another possibility is that the solution concentration is not retested when the coolant is added.

Residual fluid not properly drained

In order to prevent the chiller from freezing, some users will stop the outdoor chiller in winter, but they find that it freezes even if it is stopped. Why? Our customers have also encountered this situation. Our maintenance personnel found that they did not drain the liquid in the system or add antifreeze protection after shutdown. The residual liquid is static at low temperatures and is more likely to freeze.
 
The structure of the chiller is relatively complex, and it is easy to have incomplete drainage in parts such as plate heat exchangers and filter housings. The residual liquid will freeze first in these places, and the plate heat exchanger may crack or rupture due to expansion after freezing.
 
Some high-performance outdoor chiller systems support automatic liquid draining and low-temperature protection operation before power failure. Although some equipment has these functions, if they are not enabled, there will also be hidden dangers of freezing.

Which parts are prone to freezing and cracking?

---

•Verdampfer: The evaporator used in the chiller is usually a shell and tube heat exchanger or a plate heat exchanger. They have a complex internal structure and many cavities. Once the liquid inside freezes and expands, it will crack the heat exchanger.
 
•Water tank, water pipe and water pump: These parts are generally plastic or copper structures, which are easy to deform or crack after freezing.
 
•Filters and flowmeters: Their internal channels are very narrow. If the liquid is not drained cleanly, the residual liquid will freeze and cause them to be damaged.
 
•Solenoid valves and control valves: If there is water inside the valve body, it will freeze or crack.

Antifreeze measures for outdoor chillers

---

A chiller that needs to be used outdoors in winter needs to take adequate antifreeze measures.

Use the correct proportion of chilled water

When configuring the glycol-water mixture, it is necessary to determine the most appropriate concentration based on the minimum operating temperature of the cooling system and the local minimum winter temperature. If the system enters the air, The solution may absorb moisture from the air, diluting the concentration and raising its freezing point.

Built-in heating and insulation device

The pipes and water pumps of outdoor chillers are generally wrapped with electric heat tracing cables, and insulation materials such as polyurethane and rubber plastic are used to insulate all parts through which the liquid flows. Some equipment has a constant temperature heating system with a controller that can automatically operate at low temperatures to prevent the temperature from being too low.

Low-temperature automatic circulation function

Coolant flow rate is too slow and it is easier to freeze. Therefore, the outdoor chiller system should be set up with a low-temperature automatic circulation program. When the temperature is lower than the set value, the system can automatically start the pump circulation system to prevent freezing.

Drain the water system after shutdown

If the chiller is shut down for a long time in winter, be sure to fully drain the fluid from the circuit in the system first. This process is time-consuming, but many chillers have an automatic drainage function.

Correctly choose a low-temperature model

If your chiller needs to be used outdoors and the local winter temperature is very low. Then you should consider antifreeze when purchasing a chiller. It is best to choose a low-temperature dedicated chiller with built-in heating and insulation.

Schlussfolgerung

---

LNEYA supports customization of antifreeze functions and programs according to regional temperatures. We have customized low-temperature antifreeze outdoor chillers for many companies in Russia and North America. If you have a need, we are happy to provide you with professional solutions.