This is often an electrical heater. When the skin air will get to all-around six*c (42.8F) the heater will come on and warmth the air up to guard the factors inside of from frost. If not This may freeze the heating and cooling coils inside of and burst them. Variations https://industrialboilerhire61592.blogolenta.com/29344253/the-best-side-of-air-handling-units-ahus