Cabinet heaters provide an even distributed interior air temperature in enclosures with electric/electronic components. This prevents the formation of condensate and prevent resulting malfunctions. The heaters are controlled usually with the thermostat or hygrostat. Due to the resistance heating-element the series FH show no starting current, warm up slowly and distributed the warmed air, thanks to the built in fans, evenly in the enclosure.

https://www.fuhrmeister-gmbh.de/pdf/schaltschrankkomponenten/Schaltschrank-Heizungen_FH_Widerstandsheizungen_Fuhrmeister_DE_EN.pdf