sizing ducting

[Brian349]

I am installing a fg6tc120cvcb with a 2stage 5 ton heat pump in a 3 story 4300 sq. ft. house.I have 34 suppy air register.The fan pump out 1870 CFM.Should I down size the run the supply lines to 5 in.1870/34 =55.Questioning my Hvac contractor.

[aruddick]

Do you have any idea what you are doing? From your post I can't for the life of me figure out what you are asking :confused:

[iraqveteran]

NO DIY here. Call a contractor to supply your needs.

If you are a contractor, do a proper heat load calc using manual J and then duct design per manual D.

We can't answer a question like that here.