This is in Austin TX, current temps in the 95-100 range. Home built in the 90's, with double pane windows and lots of insulation. 8year old Lennox Signature 4T downstairs and Pro 2.5T upstairs. Located in attic. 3500 sf, with the 500sf livingroom having a 2 story ceiling.
We moved in in May 2017 and by August noticed the AC just could not seem to keep up. Our neighbors (similar builds and equipment) could get into the mid 70's no problem but we could not get below 79 and below 80 in our master, until well after dark. We identified many leaks in the plenum and i sealed those. We survived the first summer. Winter of 2017 we had a chuck and truck come out and rebuild the plenums and add dampers. They managed to get us airflow into the master, likely at the cost of the two story livingroom. Manageable at night, but still hot days.
After a rough first few months of summer here we finally called a higher end HVAC company. The diagnostic call guy checked the units inside and out and noted that refrigerant pressures were spot on and the systems seemed to be running as designed. However, we both noted across the airhandler temperature delta of only 9-12 degrees (at the unit not the registers). This didn't raise flags for them. They recommended an air balance assessment.
Testing showed less than 5% leak. Both units suffering from significant static pressure issues on both supply and return. pressures over 1.1 all around. Upstairs 2.5T only moving 600CFM and downstairs 4T moving 1000CFM. Inspection suggested that we needed more returns and supply ducts undersized. They replaced all upstairs ducts (buckets correctly sized) with 1" larger and new plenum with all home runs, pulled tight. Upstairs got a second return. Downstairs ducts are not accessible, so we added another 14" return and they rebuilt the plenum to a designed volume and shape (vs the last guys just building to fit space. We know that downstairs supply static might not be all that easy to address, though we could add another duct to the ceiling of the 2story livingroom, all other spaces are restricted.
So they finished that work yesterday and have not been out to retest static pressure or balance. But while the upstairs registers certainly seem to flow better and with less noise (new curved blade registers too), at 11am and 85* outside I am still not able to get below 78* inside. Downstairs I am in the same boat, 78-79*. In the attic, at the units I get the following splits: Upstairs: R 80*F > S 67.8*F; Downstairs: R 77.1> S 68.2F. Attic temp 85F
So all the airflow improvements in the world may not matter, As an amateur, I would think something is not right with the systems if they cannot make better splits. At the outside units, the larger copper is cool, but not close to cold. Both around 78* on their surface. For the upstairs unit the smaller copper line is a little warm, but not very. For the 4T downstairs unit the smaller line is about the same temp as the larger copper line, that is not warm but cool.
So what next? I think the outside units are not working correctly. What do I ask to check next?
We moved in in May 2017 and by August noticed the AC just could not seem to keep up. Our neighbors (similar builds and equipment) could get into the mid 70's no problem but we could not get below 79 and below 80 in our master, until well after dark. We identified many leaks in the plenum and i sealed those. We survived the first summer. Winter of 2017 we had a chuck and truck come out and rebuild the plenums and add dampers. They managed to get us airflow into the master, likely at the cost of the two story livingroom. Manageable at night, but still hot days.
After a rough first few months of summer here we finally called a higher end HVAC company. The diagnostic call guy checked the units inside and out and noted that refrigerant pressures were spot on and the systems seemed to be running as designed. However, we both noted across the airhandler temperature delta of only 9-12 degrees (at the unit not the registers). This didn't raise flags for them. They recommended an air balance assessment.
Testing showed less than 5% leak. Both units suffering from significant static pressure issues on both supply and return. pressures over 1.1 all around. Upstairs 2.5T only moving 600CFM and downstairs 4T moving 1000CFM. Inspection suggested that we needed more returns and supply ducts undersized. They replaced all upstairs ducts (buckets correctly sized) with 1" larger and new plenum with all home runs, pulled tight. Upstairs got a second return. Downstairs ducts are not accessible, so we added another 14" return and they rebuilt the plenum to a designed volume and shape (vs the last guys just building to fit space. We know that downstairs supply static might not be all that easy to address, though we could add another duct to the ceiling of the 2story livingroom, all other spaces are restricted.
So they finished that work yesterday and have not been out to retest static pressure or balance. But while the upstairs registers certainly seem to flow better and with less noise (new curved blade registers too), at 11am and 85* outside I am still not able to get below 78* inside. Downstairs I am in the same boat, 78-79*. In the attic, at the units I get the following splits: Upstairs: R 80*F > S 67.8*F; Downstairs: R 77.1> S 68.2F. Attic temp 85F
So all the airflow improvements in the world may not matter, As an amateur, I would think something is not right with the systems if they cannot make better splits. At the outside units, the larger copper is cool, but not close to cold. Both around 78* on their surface. For the upstairs unit the smaller copper line is a little warm, but not very. For the 4T downstairs unit the smaller line is about the same temp as the larger copper line, that is not warm but cool.
So what next? I think the outside units are not working correctly. What do I ask to check next?
