I’m looking to add central cooling to the first floor of my 1950’s Cape style house in Massachusetts. Current duct system and gas furnace do a good job keeping all rooms comfortable during heating season.
Some installers are happy to add central AC or HP. Others look at the ducts and claim they won’t support cooling – and propose a complete redesign or multiple mini-split heads.
Area is 1050 sq ft spread out over 6 rooms including an addition with a lot of glass. Manual J done by one installer and myself has cooling load at 1.5 Tons.
Supply ducts: seven 4”, one 8” plus a 6” to the second floor which might be removed/dampered when the second floor is conditioned with mini-splits.
Return ducts: four 4” plus two short 7” runs with 6x12” registers in the floor. Filter currently 16x25”. Registers for all 4” ducts are at the base of the wall.
Furnace is two stage. Dip switches are set for the lowest airflow rates at 800 CFM for 1st stage and 1100 CFM for 2nd. Air noise is noticeable at 2nd stage. I don’t have any static pressure readings.
I’d appreciate any suggestions on how I can better understand what my duct system could handle versus what is needed for cooling.
Thank you!
Some installers are happy to add central AC or HP. Others look at the ducts and claim they won’t support cooling – and propose a complete redesign or multiple mini-split heads.
Area is 1050 sq ft spread out over 6 rooms including an addition with a lot of glass. Manual J done by one installer and myself has cooling load at 1.5 Tons.
Supply ducts: seven 4”, one 8” plus a 6” to the second floor which might be removed/dampered when the second floor is conditioned with mini-splits.
Return ducts: four 4” plus two short 7” runs with 6x12” registers in the floor. Filter currently 16x25”. Registers for all 4” ducts are at the base of the wall.
Furnace is two stage. Dip switches are set for the lowest airflow rates at 800 CFM for 1st stage and 1100 CFM for 2nd. Air noise is noticeable at 2nd stage. I don’t have any static pressure readings.
I’d appreciate any suggestions on how I can better understand what my duct system could handle versus what is needed for cooling.
Thank you!
source https://hvac-talk.com/vbb/threads/2228369-Duct-system-adequate-for-cooling-How-to-determine?goto=newpost
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