Chiller Coolant / Antifreeze

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Antifreeze

Selecting an antifreeze (coolant) for the chiller in a metal laser cutting system.

Manufacturer and expert opinions vary. Some recommend antifreeze only in cold environments to prevent freezing; others insist on distilled water only to avoid risks. Always consult the company you purchased the equipment from — the wrong choice of chiller fluid can void the warranty.

When antifreeze is needed:

Antifreeze is only required if the room temperature can drop below +5…+10 °C (e.g., unheated shops in winter). In normal conditions (+10…+25 °C), use distilled water — it has the best specific heat capacity (4200 J/(kg·°C)) and removes heat from the laser source more efficiently.
If the temperature is always above +10 °C, antifreeze is not required.

Which antifreeze to choose:

Use specialized formulas designed for laser systems, based on ethylene glycol (industrial grade, without automotive additives such as silicates, which cause corrosion).
Clariant Antifrogen N (ethylene glycol + water) — non-corrosive to metals (aluminum, copper) and rubber hoses, with high thermal conductivity, low viscosity at low temperatures, and non-foaming.
Avoid automotive antifreezes (such as Tosol-type coolants) — they attack aluminum chiller parts and can degrade silicone tubing.
Verify compatibility with system materials: confirm there is no corrosion on copper, aluminum, rubber, or plastics. The fluid must have a high boiling point, high flash point, and high specific heat capacity.

Operating rules:

Antifreeze is normally diluted with distilled water. The standard ratio is 3:7 (3 parts antifreeze to 7 parts water), giving protection down to −20 °C. For colder conditions, increase the antifreeze share (e.g., 1:1 for −30 °C), but check with the chiller supplier — excess antifreeze raises viscosity and reduces cooling efficiency.
Do not run pure antifreeze; use only the formulation recommended by the equipment supplier — pure antifreeze is often too viscous and conducts heat poorly.
Before refilling, drain the old fluid and flush the system with distilled water.
Do not run antifreeze year-round — replace it with distilled water after winter to prevent sediment buildup.
Check pH and conductivity regularly (antifreeze should be neutral).
For freon-based chillers (CW-5000 / CW-5200 type), an antifreeze-water mix is optimal.

Risks of using antifreeze

Antifreeze helps prevent freezing (which cracks tubes, the laser source, and optics from ice expansion), but it carries risks — especially if the wrong product is chosen.

Main problems:

Reduced cooling efficiency. Antifreeze is denser and more viscous than water, which strains the pump (designed for water). This causes overheating of the laser tube or source, reduced laser power, and shortened equipment life.
Corrosion and chemical reactions. The wrong antifreeze (e.g., automotive) attacks aluminum chiller parts, dissolves silicone hoses, and forms sediment. This can burst hoses, seize the pump, and clog the cooling loop.
Bubble formation and overheating. Air bubbles can form in the pump and accumulate in the laser tube, impairing cooling and causing local overheating.
Loss of warranty. Many manufacturers void the warranty if antifreeze is used and insist on distilled water.
Toxicity and safety. Ethylene glycol is toxic — leaks are dangerous to people and animals. It also poses a fire risk at high temperatures.

Summary

If the ambient temperature stays stably above +10 °C, stick with distilled water with isopropyl alcohol added at 5–22 % of the water volume — alcohol prevents microbial growth in the tubing and inhibits freezing. Replace the water at least every 1–3 months.