This is frequently an electrical heater. When the surface air gets to all-around 6*c (forty two.8F) the heater will arrive on and warmth the air up to guard the parts inside from frost. In any other case this could freeze the heating and cooling coils within and burst them. Platelet https://ahus37148.aboutyoublog.com/34592057/top-guidelines-of-air-handling-unit-ahu-hire