>>725267663
>why is it on the ground
So the way American AC units work, they are plumbed into the existing gas-fired heating systems. The evaporator is mounted above the furnace, while the condenser and compressor sit outside, with the refrigerant pipes running underground. So it uses the same blower fan and ducts as your heating. With a reverse-cycle air-conditioning system (also known as a heat pump), it can run in reverse, treating the internal heat exchanger as a condenser, and the external one as a evaporator, allowing it to provide cheap heating in the cooler months. Once winter proper hits, if required, the actual gas furnace will take over.
Most systems like this will also have a resistive heating coil somewhere in the system to provide backup warmth should both the air conditioner and gas furnace be unable to function for whatever reason. American winters get very, very cold, to the point where it can actually cause all your water pipes to burst and flood the house, should sufficient heat not be provided. So having an emergency backup heat source that kicks in automatically is important
In short:
Air conditioning in the hottest months.
Reverse-cycle air conditioning in the cooler months.
Gas-fired furnace in the coldest months.
Resistive heating for emergencies.
All built into a single system with a single control mechanism. This is why those digital thermostats have like 16 terminals on the back, because the wiring to control all this is pretty complex.
