This walk-through follows a heat pump install from the ground up. Your job is not to do the work. Your job is to see each stage happen and to know what to ask when it does not match what you were told.
Before the crew arrives
Settle the outdoor location before the day of the job. The unit needs a level pad or stand, open space on its sides and above for air to move, and a spot away from where snow or roof runoff lands. Ask whether the pad is being poured or set on existing concrete, and who confirms that it is level. Check the indoor location too. The air handler or coil needs room for service access and a clean path to the ductwork.
Setting the equipment and the line set
The outdoor unit goes on the pad and the indoor unit goes in its place. The line set, which carries refrigerant between the two, is run and connected. Watch that the line ends stay capped until the moment of connection, because moisture and dirt inside the lines cause trouble later. Ask how the insulation is handled and where the lines pass through the wall, and check that the penetrations are sealed.
Evacuation and the refrigerant charge
Before refrigerant is released into the system, the lines and coil are pulled down to a deep vacuum to remove air and moisture. Ask the installer how long the vacuum was held and what the reading was when they stopped. The refrigerant charge is then set. Ask which method was used to set it and whether it follows the data on the unit label and the install instructions for your line length. A charge set without that check is a question to raise before the crew leaves.
Electrical, thermostat, and controls
Confirm the disconnect is at the outdoor unit and that the breaker matches the unit label. Control wiring should run to the thermostat without splices you cannot see. Ask that the thermostat is set to the heat pump mode, that the emergency or auxiliary heat setting is explained to you, and that you are shown where it lives on the thermostat. Your installer should be able to say in plain words when that setting runs on its own and when it should be used by hand.
The first run and the close-out
Run the system in cooling and heating if the season allows. Check the air temperature at the supply and the return, and listen for a steady run without a rough or cycling pattern. Ask for the readings written on paper. Before the crew leaves, get the operating settings in writing, the name of the person to call, and the install date recorded on your planning record. The Heat Pump page on this site gives typical service life and a planning guide you can set beside the install date.