This is normally an electrical heater. When the skin air will get to close to 6*c (forty two.8F) the heater will arrive on and warmth the air up to safeguard the elements inside of from frost. Normally this could freeze the heating and cooling coils inside of and burst them. https://rylancmudk.blue-blogs.com/39286389/the-fact-about-ahu-s-that-no-one-is-suggesting