This is often an electrical heater. When the outside air will get to around 6*c (forty two.8F) the heater will come on and warmth the air up to protect the parts inside of from frost. Normally This may freeze the heating and cooling coils within and burst them. Modular AHUs https://industrial-chiller-hire10864.angelinsblog.com/31498365/the-greatest-guide-to-ahu-s