I am new to this community, I was wondering, to switch on an air conditioner or garage roller door, would I use a NO or NC contactor with a sonoff.
The schematic below was drawn in the past to illustrate how to connect a 240V heater with a contactor relay and Sonoff Basic. For a 120V circuit you would use the Neutral instead of L2 and a 120V coil on the contactor.
Hope that helps.
Here are a couple more schematics you may like.