Heat Pumps & Mini-Splits
What Is Defrost Mode?
Definition
Defrost mode is a heat pump's automatic process for melting frost that builds up on the outdoor coil during cold, humid weather — it briefly reverses to cooling mode to warm the coil, which is why you may see steam rising from the outdoor unit or feel a short burst of cool air indoors during winter.
Why it matters for your home
Seeing steam from your outdoor unit on a cold day, or feeling brief cool air indoors, is normal defrost behavior, not a malfunction — our full defrost mode guide walks through what's normal and what isn't.
What to do about it
If defrost cycles happen very frequently or the outdoor unit stays visibly iced over afterward, that's worth a service call — normal defrost is occasional, not constant.
Related terms
This definition is pending licensed-trade technical review. It's sourced from our own published service and guide content, not invented — but hasn't yet been signed off by a licensed HVAC reviewer.
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