Inline Duct Fans

I’ve been considering putting an inline duct fan in my own home to some new duct work that is heating and cooling a new room over the garage. The room does heat and cool ok, but not nearly as well as the rest of the rooms on this system. So I just want to give it a boost. Of course, since the house was built with only one central return in the hallway on the second floor, it is most effecient when the doors are left open. I do hate that part about the system. I already know that many don’t recommend these fans, but I can’t afford to replace my whole system at this time. It’s 14 years old and I know that at some point in the next few years I’ll be forced to, but not happening now.

Anyhow, I’ve read quite a bit on the different ways of activating the inline duct fan. One of the methods I seemed to like was to use the 51 Aprilaire Current Sensing switch, however, it’s installation instructions tell you to clamp it to a common wire from the blower motor. I don’t see a common wire coming from my blower motor. It is a Trane system. The blower motor only has a black wire to the run cap and then another black wire to the motor, a yellow wire from the motor back to the cap and then a red wire to one of the speed terminals on the fan. If I use this method, I’m not sure on which wire to clamp it to since neither are a common wire.

I’ve also looked at using a small 24V relay to tap into the voltage from the thermostat wiring or a sail switch. I’m hoping someone looking at this can give me some good adivce on the pros and cons of each method and perhaps even recommend the best fan to use. I think Lowes has one for about $35 that’s a little over 200 cfm’s.



To start with, if you don’t have a return in the room over the garage your not going to get the room air out to the main return as the rest of the house has more pressure than the bonus room.

Next, you are trying to condition 2 floors of the house with one un-zoned system.
Can’t be done.

The bonus room has a higher heating/cooling load than the rest of the house and unless you “control” through proper balancing, blowing more air will solve little or nothing.

Install an electric baseboard heater or convectair.

I agree , the simple method some times is the best .

Well I decided to hold off on the fan and bought an oil-filled electric heater. I figured I should wait until the cooling season kicks in full swing and see how the cooling goes.

Have you tried to regulate it by simply closing or patially closing off some of the registers?? I had the same issue with my basement always being cooler than the upper floors. partially closed all the vents on the main floor and it made a world of differance.

My daughter goes and stay at My Grand daughters and the bed room is cold in the winter and hot in the summer . I got her one of these drop in fans .
She takes it with her and uses it while visiting and the bed room is great .
Her son-in-law is a difficult person so nothing is said , Works great for her .
Cost about $20;00 at Home depot.
It has an adjustable thermostat both hot and cold

Agree with what others stated, but in addition, let’s not overlook the obvious…

Since this is a room above the garage… what is the actual insulation situation???

Side note: make sure the doors to all the rooms on the second floor have a 1 to 1-1/2 inch air gap at the bottom for return air flow! You would be surprised how many people install new carpeting with nice thick padding, and nobody checks the door air gaps!!