What amount of airflow is called for with a 125,000 BTU 80% efficient furnace? It seems everything is engineered around the AC needs... but the furnace has way more tons of heating output than the AC has cooling.
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Originally Posted by Paulbstockton6@hotmail.co
Grille size 17x20 = 340sqin x 2 = 680cfm... problem
What just happened...so now you will have excessive pressure (big deal, I'm in the same boat) This will make the blower motor work hard...drawing more amps.
I predict that if you tested static pressure you will be exceeding the .50wc spec.
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The downstairs return is more noisy... actually when I went to replace the filter the first time, I found that ducting was not sealed with the wall, so it was mostly pulling unfiltered air from within the room where the furnace is. Perhaps that was left unfinished to gain sufficient airflow? I sealed it up so that all air goes through the filter from the living room.
I'll test the pressure and see where I'm at. Strangely, when I remove the air filters, the air handler draws more power.
Perhaps in the meantime I can install a higher flow filter?
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The vents on the roof top are sufficient...the soffit are not. The total vent area, say 20x.5sqft =10sqft. You need roughly 10sqft soffit area, spread about the perimeter of the roof for your attic to vent properly...rather, the free area of the ridge needs to equal the free area of the soffit at the perimeter of the attic floor.
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Soffit ventilation will be on my to-do list for this summer. Looks like I need about 25 of the 16x8" vents.
I just looked up the specs on my current soffit vents. 0.8 sq/in LOL. I'd need like 1,800 of them to be adequate. I think there's about 100 on the whole house.
In the summer, I have been opening the access door to the attic.
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R30/38 would be minimum and I'll bet they recommend double that in current codes for new houses.
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Maybe I'll add some rolls. Currently have blown in fiber. I'd want to engineer some walkways though as I'm in the attic often.
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So, since we are deficient in return air, look at the return plenum, or that 17x20 duct....can you tap into that and run an additional return somewhere where it might be benificial....?
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Maybe. There is access between the ceiling and the floor above. Seems difficult, and you probably don't put a return in an exterior wall. There's no crawlspace.