4. The SH500-20L contains an internal heater to maintain optimal solution temperature for maximum cleaning effect. The left side of the control panel displays current solution temperature (far right) and the desired temperature (center right) in centigrade scale. The red light indicates if the heater is on. Depending upon the initial temperature of the liquid in the tank, it can take a couple of hours for the solution to reach maximum temperature of 65 degrees C. To convert the displayed temperature to Fahrenheit, simply multiply it by 1.8.