What temperature should the water chiller be set to?

“Colder is better” does not hold for a laser chiller: the laser source performs best at its design temperature, and loses power both below and above it. Far enough either way, and damage occurs.

• Too warm. Reduces power and beam quality, and over time shortens the life of the source by burning out the anode and cathode.
• Too cold. Reduces power and beam quality, and the thermal stress can crack the glass housing and destroy the source instantly.

Condensation on a live laser source

A CO₂ laser source runs at very high voltage. Condensation forming on the glass and on the electrode connections creates a path for that voltage to track where it should not. This causes arcing, damages the source, and is a real electrical hazard. It is not a slow wear-out mechanism; it can kill a tube quickly.

The rule: stay above the dew point

The dew point is the temperature at which the air in your workshop starts giving up its moisture as liquid water. Cool any surface below it and water forms on that surface.

The actual rule is not a fixed number:

Keep the cooling water above the dew point of the room the machine is in, and as far below the machine’s maximum as you can while still satisfying that.

The dew point is not a constant. It rises with humidity and with room temperature, which is why this is overwhelmingly a summer problem, and why a setting that was fine all winter can start causing condensation in July without anyone changing anything.

Working out your dew point

1. Put a cheap thermometer-hygrometer next to the machine.
2. Read off the room temperature and the relative humidity.
3. Look up the dew point for that combination. Any online dew point calculator will do it, and many hygrometers display it directly.
4. Set the water temperature above that figure, with a margin.

Example. The workshop is 26 °C at 70 % relative humidity. The dew point is around 20 °C. Water set to 18 °C will condense on the tube. Water set to 22 °C will not.

Check it again when the weather changes

This is a seasonal check, not a one-off setting. A humid summer week can move the dew point by several degrees.

BRM water chillers are already set for European climates

BRM machines have their chillers set to a safe range for European climates. In a different climate you may need to adjust the temperature.

The laser source itself has an ideal range of 22 °C to 28 °C. If you would have to go outside that range to stay above the dew point, use dehumidification or air conditioning instead.

Other things that matter

Give it time to equalise. Switch the chiller on and let the whole volume of water reach an even temperature before you fire the laser. Firing into water that is still stratified subjects the source to thermal shock. A general guideline with a normal chiller loop is to wait 30 minutes after switching the machine on before you start producing. That is only needed when the temperature is outside the ideal range.

Watch for water that never gets cold enough. If the chiller cannot hold its setpoint during a long job, that is a separate fault: check the coolant level, the flow, and whether the chiller has enough space around it to reject heat. A chiller crammed against a wall cannot do its job.

The classic symptom of a cooling problem is a machine that cuts well for the first 15 to 20 minutes and then gets progressively weaker. If that is what you are seeing, look at the cooling before you suspect the laser source.

Water quality is separate from temperature, and equally important. Which water to use, how often to change it, and how to fill and empty the unit are covered in the water chiller in top condition.

CW-3000 and CW-5000/5200 are not the same machine

They are different machines, which is the answer to “why can I not set the temperature on mine?”

The CW-3000 has no refrigeration and no temperature setting. It is a radiator and a fan; it moves heat from the water into the room. It can only ever get the water close to the ambient temperature, never below it. That has one useful consequence: a CW-3000 cannot cause condensation, because it cannot get the water below the dew point. It also means that on a hot day in a hot workshop, your cooling water is hot, and there is nothing in the unit to fix that. The answer there is to cool the room.

The CW-5000 and CW-5200 have a compressor and a real temperature control. They can hold a setpoint below ambient, which is what you want, and it is why the dew point rule applies to these and not to the CW-3000. They typically offer two modes:

• Intelligent mode, which tracks the room temperature and holds the water a few degrees below it. Convenient, and reasonably safe from condensation in a moderate workshop, but on a hot day it follows the room up, so the water can end up warmer than the source wants. The power also fluctuates slightly on very long runs. For mass production we suggest constant temperature mode, which removes the 1 to 2 W variation that intelligent mode introduces.
• Constant temperature mode, where you set an absolute figure and it holds it. This is the mode to use if you want control, and the mode where the dew point rule really matters.

If your chiller is going into alarm rather than simply running warm, that is a different problem: CW-3000 alarm and CW-5000 / CW-5200 alarm.

Winter is the other half of this

Cold brings its own risks: a machine below its minimum ambient temperature will not perform, and water left in an unheated workshop can freeze and split the tube or the pipework. That side is covered in can the laser machine and water chiller withstand the cold?

A seasonal checklist

When	Check
Every startup	Coolant level, flow, and that the chiller is running before the laser fires.
Start of summer	Measure room temperature and humidity, work out the dew point, and raise the water setpoint if needed. Confirm the chiller has airflow around it.
During hot spells	Look for condensation on the tube and its connections. If you find any, stop and raise the setpoint.
Start of winter	Make sure the workshop stays within the machine’s ambient range, and protect against freezing if it does not.
Periodically	Water quality and replacement. See the water chiller in top condition.

On a BRM machine

BRM machines come with predetermined water settings, which are correct for the majority of customers. On the newer generations the stock chiller is oversized further, so that hot locations, including equatorial ones, are no problem.

We deliver the chiller in intelligent mode by default, because condensation is the risk that needs constant checking. If you need the power stability and accept the extra inspection, switch it to constant temperature mode.

If you are unsure what your machine wants, or you have found condensation on the tube, contact us with your machine model and serial number.