5 ton 120k BTU furnace. 2 year old house
HO has pretty low airflow through the registers, everything seems to be sized properly on the main branches for supply and return, but there's around 24 supplies in this home all with 6" round and 4x12 registers, and the return is all properly sized up above, but when it transitions into the return 90 at the unit, it tapers way down (I'm guessing because there is a clean out in the way). It, also has a 12 inch round return for the basement on the other side of the furnace not in the picture. I'm wondering if this place has too many registers or if this trainsition on the return could be the culprit, any thoughts?
The airflow at the registers seems okay but it definently feels less than normal. It's pretty loud when it runs too. Thanks!
Is the only problem low airflow from the supply diffusers?
The owner wants to feel the air coming out of the vents?
What did the owner say the problem is??
"Compressors never die; they're always murdered!" - Glenn Hannegan Jr
Is the only problem low airflow from the supply diffusers?
The owner wants to feel the air coming out of the vents?
What did the owner say the problem is??
They're ac leaks refrigerant so it was a no cooling call, but theyre side complaint was airflow, theyre up and running now with the leak fixed
With 24 diffusers airflow per diffuser will probably be less than 100 CFM even with no duct problems. If the house cools properly there is no reason to worry about the airflow per grille. With that many diffusers the loud noise is most likely in one area. That appears to be at the furnace return. That doesn't necessarily mean mods have to be made to the duct to get enough airflow. The noise is whatever the owner can tolerate as long as flow isn't overly restricted.
No man can be both ignorant and free.
Thomas Jefferson
OK, my question is, the return duct gets narrower and then goes into the 90* then into the unit, Is this normal in some areas? All of the systems here that I work on, the return doesn't reduce down like that, even the commercial systems, unless they split off, and I am pretty sure, when you restrict the airflow, the system gets louder also.
Yep 12 inch round on the other side basically 90s straight into the return grill downstairs with a 16x20x1
The pictures filter is 16x25x1
If all it’s going on for return air besides that single undersize boot is a 12” round sucking air from one room then I would say that is probably no beuno, needs a bottom return box and a much bigger boot to meet spec
One inch pleated air filter?
Check static pressure and velocity.
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24 x 6: supplies... is somewhere in the 1750-1800 CFM's area... a little light for 5 tons... however enough to have good aiflow... IF there was enough air to flow...
As noted earlier... 5 tons of airflow needs either both sides or one side + bottom inlet!
You will need to talk them into one of those return plenums that raises the furnace about 10-12" off the floor... and feeds air into both the bottom and the side.
AND... the smallest filter you can use... is 20x25x1...
A 20x25x4 or 5 media would be better!
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Originally Posted by Spide
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