Every heat pump has a specific external temperature range within which it can operate safely and with acceptable efficiency.
What is low ambient cut-off
It is the limit below which the controller may restrict or stop heating operation to protect the refrigerant circuit.
It is not the same for all models
Some units are designed for very low temperatures, while others have a smaller allowable range.
What happens near the limit
Available power may decrease, defrost frequency may increase, and auxiliary heating may be activated.
Correct evaluation
Always use the performance tables and the operating envelope of the specific manufacturer.
