What is an SSR? Solid State Relay. It passes power without contactor surfaces opening and closing. SSR’s have a distinct advantage over mechanical contactor relays in that they don’t have any moving parts banging into each other. That allows for a relay that can run longer and not wear out. They switch at a much more rapid rate than the old relays, providing potential for much more accurate heating systems, resulting in more predictability and stability to your processes. Once a signal is received in a SSR, it will apply voltage to the heater much faster than an old fashioned mechanical or mercury displacement relay. A typical Reimers design will have multiple heating elements and multiple stages to bring them on and off. The fine tuning is done by the SSR stage allowing from 0 to 100% of the heating capacity to be used rather than having only 0 power or 100% power like old systems.