How do I install into a sealed enclosure? 

Soft starters can be installed in sealed enclosures provided the ambient temperature within the enclosure will not exceed the soft starter's rated temperature.

Heat generated within the enclosure must be dissipated, either through the enclosure's walls or by ventilation. When calculating the heat generated in the enclosure, all heat sources must be considered (eg soft starter, fuses, cabling, switchgear etc). The enclosure should be protected form direct sunlight to prevent external heating.
To minimise heating, most soft starters are installed in bypassed configuration.

AuCom’s WinSTART program includes a function to help design enclosure ventilation.