Normally, the heater option must not be changed for any reason. Due to some P802-18012 were modified to work with NUVOGO™1000 machines, it might happen the chiller is delivered without heater option. The heater option was turned of during the modification. If the P802-18012 is connected to a 16W Coherent™ Laser the heater option has to be on.Please keep in mind, without the interlock cable or whilst the laser is in standby, the P802-18012 heats the cooling water to 29°C. When the interlock cable is connected properly and the laser is switched to normal operation, the chiller is set to the “set point” temperature.