I moved into a house about 2 years ago and noticed this yesterday.

In the master bedroom system, which is located inside the 2nd story walk-in attic, the other two are in the "3rd floor" attic.

There is a small dial next to the light switch which when i turn it I can speed up the flow of air in about a 4" piece of ductwork, which is blowing into the attic. I have played with that dial before and never noticed any air blowing nor did I really ever notice that duct.

I recently had that unit replaced. Is this some sort of attic fan? I am not sure what the duct work is connected to as it requires some dedication to get back there.

Anyone ever had something like this?

It sounds like it is an add-on fan to address a specific problem. some area that doesn't get enough airflow otherwise.

It may be an exhaust fan meant to pull air out of a particular space like a bathroom.
It may also be a way to force a small amount of fresh outdoor air into your system whenever it's running.

Either way, you'll want to know where the air to the fan is coming from, and where it is going to.

just call the installer?

Installer came and they are stumped. We think it might have ran to that bookcase to cool electronics. He said he had never seen anything like that before.

Is the attic conditioned space? Was there a temp or humidity problem there?

No the attic isn't, not sure about humidity issues as we haven't experienced any but only been here a year or so.

If I subscribed I'd post some pictures, but the cabinet/entertainment center which is cut into the attic has some sort of built in motor/electrical gang box, which none of the installers knew what it was but it appeared the duct work went to that

Sounds like someone was trying to passively cool some electronic equipment. Feel free to text me any pictures and I don't mind looking at it. Many times we will add supply air to media closest with a damper to not allow air to flow in heat mode. I definitely wouldn't run it without a reason as you're just making the interior of the house negative which will allow infiltration of outdoor air.

Caleb
979-422-0148

i'll send some pictures later today

I am going to pull the fan or whatever it is out of the cabinet and try to re-engineer this thing