The chiller is the component that decides how long the source lasts

Buyers evaluating a laser system compare source specifications closely and treat the chiller as an accessory. That inverts the actual relationship, because the chiller determines the thermal environment that governs how quickly the source's pump diodes degrade.

The sensitivity

Semiconductor laser diode lifetime is strongly temperature dependent. A widely used approximation is that lifetime roughly halves for each ten-degree rise in junction temperature. Junction temperature follows coolant temperature, coolant flow and the thermal resistance of the path between them.

A source rated for 100,000 hours at its design coolant temperature will not achieve that if the coolant runs warm, and the shortfall does not appear for years.

Where systems fall short

Ambient derating. Chiller capacity is specified at an ambient temperature. In a workshop running warmer than that — common in summer, or where several machines reject heat into the same space — actual capacity is lower than nameplate.

Fouled heat exchangers. Dust and oil mist accumulate on condenser coils, reducing heat rejection progressively. This is the single most common maintenance omission.

Coolant condition. The wrong coolant, or an inhibitor package that has depleted, causes corrosion and biological growth in cooling passages, restricting flow. Flow restriction raises junction temperature even when coolant temperature reads correctly.