Lg air conditioner does not heat as good as the dose unit defordt goed for all so it can often be the snow outside temperature is -3. Well, I have the answer. As you say I think heat is talking about a heat pump no A / C. If so, that's normal. When below zero does not exist outside of the tire to heat the house. Thus all the heat coming from the electrical heat strip. No reason to run in normal mode. When below freezing, it is recommended to run the emergency heat mode running on electric heating mode only kicks off the compressor. Running the compressor when too cold is a waste of energy. It just freezes and thaws produce little or no heat from the compressor. What you are experiencing run in normal mode is there a kick start before the heat kicks. So making 70f, run and runs as the temperature drops. Once it hits as 67f, starting in electricity, but only bring it up to 68f and return to the heat pump produces heat. In emergency mode will bring up 70f but using only electric heat. I hope that makes sense to you. Good luck.