A solid state relay switches a load with semiconductors instead of moving contacts, so it switches thousands of times an hour silently and without wear. That makes SSRs the standard way to control heaters on plastic machines, ovens, sealers and extruders, usually driven by a temperature controller's voltage-pulse output.
The Fotek SSR is one of the most widely used relays in Pakistani panels. The code is simple: the number is the load current and the letters the control and load type. SSR-40DA is 40 A with a 4–32 V DC control input switching an AC load; SSR-25AA is controlled by 80–250 V AC; SSR-xxDD switches DC loads. -H versions handle loads up to 480 V AC.
An SSR must be mounted on a heat sink sized for the load current, and we recommend derating for hot panels. Send us the heater current and supply voltage and we select the relay and heat sink.