Solid State Relay (SSR)

A solid state relay (SSR) has no moving parts. It is a transistor activated by a small AC or DC control signal produced by the temperature controller. This type of relays can switch up to several hundred amps in less than a second. They're used for heaters with low mass like radiant heaters (but not quartz tubes and quartz lamps which require a silicone controlled rectifier) and air heaters which require very frequent power switching. Solid state relays are usually mounted on a heat sink to dissipate the heat they generate. If several of these relays are mounted in a control panel, ventilation or even cooling of the control panel may be necessary.

Advantages over electro-mechanical relays:
  1. faster reaction time
  2. increased life time of relay and heater
  3. no sparking during turn on

Infrared comparison

Comparison of different infrared heaters

solid state relay with heatsink

SSR and temperature controller