The previous Basement Laboratory generally stayed above 60 °F = 15 °C, so I set the LightObject water chiller’s low-temperature alarm accordingly.
Having reached the point where I can set up the laser in its new home, I connected the chiller tubes, filled the reservoir with distilled water (and a squirt of algaecide), connected the alarm wiring, turned it on, and had the cool water trigger an alarm:
Which was relayed to the controller:
Silencing the chiller’s alarm clears the error indicator in the controller, so it’s possible to Fire The Laser with too-cold water if necessary.
As with the previous icemaker chiller, plotting the water temperature as a function of time shows the pump adds some energy as it moves the water around the loop:
The gap in the data shows where I had a few other things to do, but the exponential rise is obvious. The chiller compressor starts at just over 21 °C and stops at just under 20 °C, so the exponential curve had gone about as far as it could go.
The numbers in the upper right of the plot give the weight of:
- An empty water bottle
- A full gallon bottle
- The partially empty bottle used to top off the reservoir
- How much water went into the chiller reservoir
The figures in the bottom mash the initial slope of that curve together with the weight of the water to find the 21 W required to heat the water at that rate, with a bank shot off British Thermal Units because why not.
A Kill-a-Watt meter shows the Q600 chiller draws 36 W with the pump running, which includes the controller and a column of blue LEDs behind the water level tube.
The pump (in the lower right) isn’t exactly water-cooled, but it’s not losing a lot of heat through that foam wrapper and maybe most of the heat really does come from the motor:
The basement temperature will rise as Spring becomes Summer, so the chiller will start working right away, and it’ll definitely get more exercise when the laser starts cutting again.
The Smell of Molten Projects in the Morning 
So I’m very curious, at what temperature is the cold water actually a risk to the laser? Is the risk thermal expansion causing fatigue, or something else? I mean obviously if it was frozen that is not going to work, but how is the minimum safe level picked?
AFAICT, the temperature doesn’t make much difference within 20 ± 5°C, so I set the thermostat for 20 ± 1 °C and the alarms at 15 and 25 °C. If it were in a normal room, rather than an unheated basement at winter temperatures, it would be perfectly happy.
The chiller starts to lose traction during relatively high-power jobs lasting longer than a few minutes, so I think it’s underqualified for a 60 W laser, no matter what its specs say.