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cleininger 12-11-2006 09:49 PM

Wiring inline duct fan to blower motor
Hi folks,

I recently purchased an inline duct fan for a chilly room in our home and want to wire it to the furnace blower motor directly.

After studying the electrical schematic for a while, I thought I had it figured out. I connected the hot and neutral to the very posts on the control board that appeared to match what was feeding the blower but got nothing... it seemed I had completely broken the connection.

Anyone out there have any advice as to where I can connect these and how to connect them?

The schematic scan was too big to upload here so I've included a link to it: HERE

I've highlighted the wires I thought would work - orange goes to "HEAT", white is going to "NEUTRAL". the other 3 are going to "UNUSED MTR LEADS" and the "COOL" switch.

Any advice would be appreciated.


mdshunk 12-11-2006 10:34 PM

How big of an inline duct fan (in terms of horsepower, watts or amps) are you using there? The "heat" and "neutral" are the correct terminals on the board that are energized when the blower is to run in heating mode. I am concerned that if your furnace blower also no longer runs, that you may have overloaded the little relay for the blower on the furnace control board. Those boards are pretty much sized with components to control just the furnace stuff only. Adding additional load to the board that was not intended to be there might not be a wise idea. Better to use those terminals to switch a relay of your own, rather than the additional motor directly. Either that, or use a sail switch in the ductwork.

cleininger 12-12-2006 05:53 AM

Thanks for the reply.

The furnace blower still works... just not with those 2 terminals disconnected. Once I returned the two disconnect terminals back to their places everything was fine. I had unplugged them and plugged the fan wires to them instead to test if it would come on in place of the blower. I didn't even get the usual hum from the furnace when I pressed the panel saftey switch.

The fan is a 6 inch, .35 amps, 250 CFM. Quite small actually.

rakes9720 12-12-2006 07:55 PM

Some furnaces have a separate relay for an Electronic Air Cleaner. You can use this if you don't already have an air cleaner installed.

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