First off, I have no idea if this is an inappropriate forum for this question, so please redirect me if there is a better group for this.
I've got an old (1970's) gas-fired forced-air furnace in my basement. It has, as one might expect, a single-speed fan motor. The motor is a 1725rpm1/4hp. During the winter we heat primarily with wood. We have a woodstove in the livingroom, and for the past few years have turned the furnace fan on during the day to circulate the heat to the rest of the house. We plug the cold-air intake during the winter, because otherwise we get outside-temp air mixed with the recirculated air which can have more of a cooling than heating effect when it's 0F outside. The house is >60 years old and has plenty of air leaks already, so please don't bother warning me about plugging the cold air intake... we've been doing it for years and nothing's broken down and everybody's still alive.
I'd like to switch my fan motor to a two-speed for a number of reasons. It will allow me to re-connect the cold air intake to the furnace, it will lower my electricity costs as I don't need the furnace fan on full speed just to keep heat ciruclating, etc. The problem is that the only motors I see available are 1725/1140rpm motors. 1140rpm is too fast for me, and will definitely still pull in too much cold air, plus I doubt I'll save that much $$ using it. I was thinking more like 500rpm.
So, first off I'd like to know if anyone knows of a manufacturer (and even better a retailer) who sells such a motor? I have been perusing the internet for an hour and while I see references to multi-speed FURNACES I don't see any mutli-speed motors for sale (other than the aforementioned1725/1140 motors).
Secondly, how do the multi-speed newer furnaces which run at a low speed all or most of the time deal with the cold-air intake issue?
I don't want to invest a pile of money in this ancient furnace, which would preclude any type of microprocessor-controlled, sensor-driven, cfm-regulated, variable-speed ECM motor system... I just want a two-speed fan to circulate the air and not pull cold air into the house and which switches to high speed when the thermostat kicks the furnace on.
Thanks in advance for any replies.
Dave British Columbia, Canada