On Aug 14, 1:15*am, "Rick" wrote:
wrote in message

...





A friend has a house with two gas furnaces and AC.
The downstairs one is OK, the upstairs which is based
in the attic is very marginal at best. *The biggest problem
is that there is not enough air flow. *It's really only a
problem in AC season, when it takes a very long time to
cool. *It has to run most of the day just to keep it at
85.

It would appear that
is due to a number of factors. * The way they did the
ducting is far from optimal. *Right off the furnace the duct
makes two 90deg turns, then feeds down a long duct off
of which come flex hoses that feed 5 bedrooms and two
baths. *The furnace is located close to one long side of
the house. *Three of those supply hoses have to go
up close to the peak of the roof, going across to the
other side of the house. *They did that to avoid going
straight across the attic floor, leaving space for walk-in
accessibility, which is good, but it comes at a cost.
The return ducting is good. *The AC itself appears to
be working, the air coming out is 15 deg cooler than
going in, closer to 20 deg right at the unit.

So, looking at this, I can see some possible improvements.
Obviously doing something with the ducting would be
beneficial. *But I also looked at the blower and right now
it's a 1050 RPM 1/3 hp. *I'm thinking part of the solution
could be to go to a 1650 RPM, 1/2 hp, which should be
a drop in replacement. * I know it's not a total solution, but
even if the ducting stuff is straigtened out, given the length
of the runs, etc, I think having the more powerful blower
would still be part of the solution. *Being that the blower
motor is easy and cheap to do, I wonder if it makes sense
to just try it and see how much it helps?

Unfortunately the horsepower required to turn the same blower at the faster
speed varies as the cube of the speed ratio. Depending on where the system
restriction curve falls on the blower performance curves, 1/2 HP probably
ain't gonna get it.- Hide quoted text -

- Show quoted text -

That's interesting. I figured it would go up, but
wasn't counting on that much! Fortunately the sub
motor is 3 speed and the lower speed is probably
1300 rpm or so. Maybe that will be OK at 1/2hp