Friday, 25 September 2020

Got brand new AC ducts and new furnace, but AC temperature split got worse?

Bought (old) 1400sqft house in 2016, replaced AC system with a Bryant 3-ton, single-stage, 16 seer.

Chose not to change AC ducts or furnace at that time. Old ducts in the house = all metal ducts. I understood the old furnace with old blower would also reduce efficiency of my newer AC.

Performance was somewhat decent. I usually set temp at 77F. Measured return air = 76F, supply = 61F, split = 15F.. Only complaint was that bedrooms = always 2F hotter than living room, possibly due to worse insulation in bedrooms or lack of return air (whole house has one single return located in hallway outside the bedrooms).

Decided this year to replace the furnace as well as all the ducts due to mold/bacteria concerns. Today, the HVAC contractor I hired:

1. Replaced all my old metal ducts with R8 flex ducts. They closed one of the ducts from my living room/kitchen area to direct more airflow toward my bedrooms.

2. New plenum, with a UV light installed in it.

3. Replaced old furnace with new Carrier 80% 90000 BTU, single-stage gas furnace (model 58SB0A090E21--20).

After the job is completed, the air flow coming from the vents feels stronger than before. But now return air = 75F, supply = 63F, split = 12F. Temperature in bedrooms is now about 1F (instead of 2F) hotter than living room. Additionally, I noticed that indoor humanity went up from 45% to 48%.

I questioned them before the techs were about to leave and they told me 12F split is normal for the house.

I have not had enough time to judge the cooling efficiency/comfort level/energy costs etc.

But I'm a bit skeptical about the worse split. Is it normal for my situation? I'd expect that after spending $5k+ on the new components, things should work a bit better than before, not worse.

Your advice would be greatly appreciated.


source https://hvac-talk.com/vbb/showthread.php?2222484-Got-brand-new-AC-ducts-and-new-furnace-but-AC-temperature-split-got-worse&goto=newpost

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