How do I know if my ac/furnace/ heat pump is hooked up correctly

[TGM]

So I have a Nest which ran my ac/furnace perfectly for years, however the ac/furnace died and needed to be replaced.

Replaced it with a ac/furnace/heat pump.

So far ac works perfect and I assume the gas furnace will work (hopefully not a bad assumption)

But how do I know if the heat pump is hooked up correctly and will work, never had one before so not sure how they start up and run, the installer wanted to sell me their $400 thermostat and dump the nest. So they weren't really helpful

[CoolingWizard]

@TGM , basically a heat pump is an air conditioner that can run backwards and become a heater. Your HVAC contractor would need to connect one additional thermostat wire to your Nest Thermostat. That is the O/B wire. It is this wire that gets energized to switch the heat pump from cooling to heating or vice versa. There basically two type of heat pumps. Those that are Air Conditioner by default (B models), and those that are Heaters by default (O models). You need to go to your Nest Learning Thermostat and do the following: wake up the thermostat, go to SETTINGS > EQUIPMENT. At this point you should see a representation of your backplate. You should see wires attached to Rc, C, G, Y1, O/B and possibly W2.  The wedges with the terminal letters should be Green. If any are Yellow, we need to make some changes.  Report what you find and we will proceed from there.

The AC Cooling Wizard