The problems are known, many times the MOSFET is faster hot than the, or the heating lasts forever;)

As a solution to these problems, there is now the RHCS, similarly built a module as an SSR but with a few advantages:

• If a fault develops easily repairable
• Can genuine 30A in continuous operation without additional cooling
• PWM compatible (Marlin / Repetier)
• Open Source Hardware, Eagle files are available. Consciously simple design, even on a breadboard board built up   Most on the market SSR in this area did not even create the currents specified with massive cooling since only inferior MOSFET are installed.Also PWM is hardly possible. The built-in high-performance MOSFET RHCS has an extremely low RDS (on) and therefore provides these currents with a small heatsink.

Specifications.:

• Continuous current 30A, briefly up to 40A possible
• Voltage range 11 - 28V DC
• Screw 6mm² fit
• PWM compatible (Marlin / Repetier)
• 1 x LED for input voltage and 1 x LED for triggering Heatbed
• Through galvanic isolation with optocoupler simple connection directly to the MOSFET outputs of RAMPS (or similar).

Possible options:

• Connection of a very low 12V Heatbeds
• Connection of a 12V to 24V Heatbeds
• Connection of up to 6 x 24V Heatbeds (very big printer)
• Connection own Heatbed constructions

Thus, e.g. an existing Heatbed operated in 12V mode 24V, thus, benefits of more than 500W at Heatbed possible. Heating time at 120 degrees for about 30 seconds. ;)

Thus, no fiddling with the 230V mains necessary.