:confused: How can I tell if my HVAC system is one or two stage? The model of the air handler is: nfcx3600c2. I am installing a home automation system and it requires this information

That is a air handler only. What is the outside unit number. When you find it look it up on Google to see what you actually have.

If you have a electric furnace inside and a heat pump outside then you have 2 stage heat.