I'd like to think I understand how heat pumps work decently well. My home has one plus electric heat, which I try not to resort to because heat pump is more efficient, if slower.
When a traditional thermostat calls for the heat pump however, it turns on the big fan in the basement at the same time as the heat pump (or perhaps it's the heat pump calling for the fan right away when it's called on to pump heat). This uses electricity and makes nose to just to move cold air while the heat pump builds pressure and starts to heat the coils in the basement.
Couldn't a delay be added, or a thermocouple added to the indoor coils, so that the fan indoors doesn't run until the indoor coils are nice and warm?
For that matter. I would think the outdoor fan could be delayed a bit too to save electricity and reduce noise at the beginning of a cycle while a temperature delta builds up.
I realize that if you ran the heat pump or AC for 'too long'/indefinitely without the indoor fan, it could damage the system. But why don't heat pumps run for 'a bit' BEFORE starting the air circulation fan?
I could understand parts cost of a thermocouple (though that's what a marketing department is for), but just using an delay wouldn't cost any money, and would be pretty easy to add to the firmware, I would expect.