Most CO² lasers operate best between 16°C and 19°C.
If it gets warmer than that then you’ll need the ability to cool below ambient temperature. As noted the CW-3000 can at best return the coolant temperature to near the ambient temperature.
When it gets colder than that then you need the ability to warm or heat the coolant. The difference between cooling and heating is cooling is only needed while the machine is operating. If the ambient temperature is near or below freezing then the heated coolant must circulate not only in the chiller/heater and the laser tube when the machine is operating but also during non-operational times to keep the chiller/heater, laser tube and water lines both inside and outside the machine from freezing and bursting.
SA makes a combination chiller/heater but the are pricey. Some users remove the fill cap from the top of the chiller and insert a thermostaticly controlled aquarium heater inside the tank. Others like myself have used thermostaticly controlled external inline heaters that are inserted into one of the water lines. In any case the chiller unit must be left running to circulate the coolant.
There is much debate about adding different kinds and brands of antifreeze to the water. I don’t for three reasons; glycol is the only one that doesn’t significantly alter the conductivity of the water which can cause arcing, adding even glycol will void the warranty on your laser tube and possibly your chiller, but mainly if you use any of the mentioned methods to heat the circulating water there is no need to add any type of antifreeze.