I am looking for a Relay Expert for my AC

[buildinga55]

I have wired my entire truck and everything is going well. Except I am totally confused about if I need a relay and how to wire it if I do for my AC unit. I have a Southern Air Superfrost unit. By the time you plug in all the pre-wired wires, you have two wires, a red power wire with an in line 20 amp fuse and a black ground wire. All of the switch and thermostat are wired in the switch enclosure. I understand you normally want relays for high power items. Maybe this is not considered high power since it only has a 20 amp fuse, I don't know.