iMO - Depends on the unit. Some stage 2 is a whole separate compressor. Some are same unit running at higher capacity and some are referring to supplemental electric coil heat.
I am not sure what two stage means in HVAC, but 2 phase is a term not used to describe 230 volts. 115 volts is single phase, 230 volts is 2 phase (but electricians don't use that term) and three phase power can be either 230 or 460 and higher volts. Single phase = one hot one neutral. Two phase = two hots no neutral and Three phase = three hots no neutral.
ok thanks.
can i tell easily and for certain by putting the 2 40 amp fuses in (required for 3 ton) instead of the current 2 60s in now(required for 5 ton) and turning on the Aux heat ? .Its a 2 stage unit though .and has a second set of 60 amps for 9.5 kw heat kit(correct size )
if its 5ton would it then pop the 40amp ac side fuses?