Duct square to round to square flow question

unixb0y

Our house was built in 1945. The supply registers are located on inside walls. While the returns are on the outside walls.

I'm planning on relocating our furnace to the other side of the basement (where the gas line enters the house)

The location of where I'm putting the furnace is at the end of the supply and return trunks. The length of the trunks are about 24'.

The supply trunk is square and has the adjustment dampers built in. The supply lines are rectangular and connect the trunk. The supply lines are no more than 3' from the trunk and go the first and second floor.

I'd like to know this before the HVAC person comes.

Since I will need a new supply and return trunks, can the square supply trunk go to a round line(with built in damper) and then transition back to square when going up to the first and second floors? Does it affect flow?

veesubotee

Speaking as a homeowner, my ductwork (built 1998) goes from square trunk to round run. At the outside wall, the round duct transitions to an oval duct of sufficient size. The limiting factor is the width of the wall.

V

beenthere

It will have some effect. How much depends on the transition method used.