Hi Bbaobaob,
Yikes! Here's an explanation for you.
A cold temperature lockout is a feature of heat pumps and it avoids operating an outdoor unit at very low temperatures. This is done so as not to damage the heat pump parts and to ensure that it remains efficient. During the operational period of a lockout, the system depends strictly on the auxiliary heat source. The auxiliary heat may fail or be inadequate leading to drop in the ambient temperatures of the rooms. Ensure that you also find out whether your heat pump has a separate low-temperature lockout option that can be used if need be. At intervals, heat pumps undergo defrost cycles in order for them to unfreeze the frozen frost or ice that has accumulated in the outer component of the machinery. In the fourth cycle, the outdoor unit may switch to the cool mode causing cool air into the space to be blown. However, the defrost cycle should not take too long and the system should return back to heating once the cycle ends. Learn more about this here in the Heat Pump Balance article.
In addition, something may be wrong with your thermostat, like setting errors, bad temperature sensors, and non-working control board. Verify the thermostat setting and make sure the temperature differentials and supplemental heat settings are properly adjusted.
Let us know if you have any other questions.
Best,
Zoe
