Heat Sink Fins should be in vertical position. So that hot air flow from bottom to top - self cooling Keep 20mm gap at top and bottom of heat sink. Apply Heat Sink compound between SSR and heat sink The screw should tight properly so no air gap between SSR and Heat Sink 1800 Square mm of total exposed aluminum is sufficient to dissipated one watt of heat generated

If SSR current capacity high and SSR use for lower capacity of load current than heat sink size will reduced
Example:
1). 50Amp SSR used for 15Amp Load Current than “B” Type of Heat sink.
2). 50Amp SSR used for 25Amp load current then “C” type of Heat Sink.