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goober49
Ductwork for old house, recommendations

I am looking to install a central ac in my 80 year old home. there are no ducts in the house at all. The walls are plaster so I want to stay away from them.

My 2nd floor closets are right in the middle of the house so i can run the ducts from the attic thru the closets.

My question is....for a typical 3-4 ton unit, what size ducts do i need? Can I use 6" round? Im trying to stay away from the giant solid ducts that you see in new homes. I dont want to 'burn out' the unit if the ducts are too small. I realize that if i choke off the output of the ac it may possibly hurt it.

Lastly, the return would be in the 2nd fl hallway which puts it right in the middle of the open attic floorspace. What size should the return be? Maybe I can keep it small and box it in with the central beam?

JLMCDANIEL
Re: Ductwork for old house, recommendations

You might want to consider a split unit instead.

Sizing duct work requires a pretty knowledgeable technician.

Jack

Bob Gabrilson
Re: Ductwork for old house, recommendations
goober49 wrote:

I am looking to install a central ac in my 80 year old home. there are no ducts in the house at all. The walls are plaster so I want to stay away from them.

My 2nd floor closets are right in the middle of the house so i can run the ducts from the attic thru the closets.

My question is....for a typical 3-4 ton unit, what size ducts do i need? Can I use 6" round? Im trying to stay away from the giant solid ducts that you see in new homes. I dont want to 'burn out' the unit if the ducts are too small. I realize that if i choke off the output of the ac it may possibly hurt it.

Lastly, the return would be in the 2nd fl hallway which puts it right in the middle of the open attic floorspace. What size should the return be? Maybe I can keep it small and box it in with the central beam?

Duct size for the rooms depends on the (airflow) need. Like JL said, you'll need someone with expertise.

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