A/C and reverse heat. In fact I chose to replace the circuit that uses other items first, such as outlets, microwave and inverter-battery charger because the AC circuit will not be in use until latter in the season and the parts were back-ordered. The entire installation was done from boat side, except I had to go into the lazarette to loosen the wire stain relief because i could not get to the screws out of it with a bit of a short leeway in the feed wire to the circuit panel. Maine Sails step by step photo essay was the guide for my installation.