The EK heaters work by means of a resistance wire. We often get questions about this heater because the coil does not glow and thus does not seem to work. Only, these coils also do not glow when switched on, but do produce heat.
This heat is blown into the room. As the heater keeps heating the air in the room by a few degrees, the heat blown out may feel lukewarm at first. The air circulates in the room, heating it a bit each time. In this way, the EK heater eventually heats the air to the desired level.