On Mon, 18 Feb 2008 21:05:47 -0500, Don Wiss
wrote:

On Mon, 18 Feb 2008 19:03:00 -0600, CJT wrote:

mr. spam wrote:

I want to replace the fan motor with a 2 speed one

i want to add a switch to the furnace so i can have the fan on all the
time in slow speed. then when the burner or the ac comes on it will
change to high speed.

I think many (most? all?) furnace/AC combinations already incorporate

Not mine, although it is quite old.

dual speed fans. Are you sure it doesn't already have the capability
you seek? You might just need an appropriate thermostat.

I believe you are correct. The heat uses the low speed and the AC the high
one.

Hmmm. That would mean that., if he has to change something in the
furnace (air handler?)** either he should make his change a little
more complicated, or he'll be using the high speed for heat as well as
AC. And I guess the designers don't think that is good. I'm not
assuming here that just because it's winter, his goal is to change the
heat and not the AC.

**And if he did half his testing in the summer and half in the winter,
he'd be especially likely to be wrong.

OP, do you plan to use this when the Fan switch on the thermostat is
in the ON position? Do you want High speed for the heat? I don't
know why they use high speed for the AC, but it seems to me that while
you would get more hot air with the fan on high in the winter, the hot
air wouldn't be as hot as if the fan were on low. So that part seems
like 6 of one, a half dozen of the other.


Don www.donwiss.com (e-mail link at home page bottom).