On 12/6/2016 8:39 AM, trader_4 wrote:
On Tuesday, December 6, 2016 at 8:17:17 AM UTC-5, cln wrote:
I did a quick math on my Furnace. Even when adding the air exchange vents, the air return is not even close to the same as what is fed in the floor vents and such. if I'm generous it may be 3:2 ~ out:return

I'd also like your opinion on if this should be replaced for efficiency?
Furnace is a late 1980 wood/electric Newmac.

IDK that it's a simple as that, ie that the intake area should equal
the output. There are more outputs because the heat/cooling needs to
be delivered to certain areas, while the return air intake locations
can be fewer and are not as critical. To deliver air to all those
places requires at least minium size ducts and registers. So, I would
not be surprised that the outputs would add up to more than the intake.
If there is some guideline, I've never heard it. The important thing
is that there is sufficient duct capacity for the blower size. If
you meet that on the intake and output, not sure that it makes a lot
of difference if you have extra outputs. Whether you meet it or not
can be determined by calculation or measured by pressure drop.




http://www.johnrwhite.net/three%20st...t%20sizing.htm