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
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.
Don www.donwiss.com (e-mail link at home page bottom).
Actually mine has several speeds, not sure how many. only three can be
controlled from the thermostat however. By moving wires around on the
circuit board you can change which speeds are used for which events. I
think the way it is set up now, if you command the fan "on" from the
thermostat, it runs at a low speed, in "heat" mode it runs at a
medium-high speed, and on A/C it runs at the highest speed.
I have on occasion found it useful to command the fan on even when the
furnace is not running, e.g. if someone is doing a lot of cooking in the
kitchen on a cold day it can be cold upstairs because the thermostat is
on the first floor, keeping the air circulating not only cools the
kitchen but tends to even out the temperature throughout the house.
I've also completely closed the supply dampers on the first floor, but
that's primarily because of the dramatic difference in insulating
properties between the first floor (block walls with brick facing) and
the second floor (sticks 'n' shingles) - I do plan to have the second
floor insulated but not until I'm done fixing all the wiring.
Anyway back to the topic at hand... it sounds like the OP does need a
new thermostat, and probably also needs to pull a new cable between the
thermostat and furnace to allow for more functions. (typical heat only
scenario would only require two wires, but heat/cool/fan only would
require at least four.)
nate
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