It really is amazing how many people become “HVAC experts” when it comes to installing a residential air conditioning system.
“Don’t call a contractor, just do it yourself.”
Unless you are an expert with not only the system but grounding cable and wire as well, we suggest not doing it yourself. These appliances require an earth connection to reduce the possibility of electrical shock. Part failure can leave you with a lot more problems (shock, burns, even death) than just a warm house.