DaveHo

HVAC question

Two story house, forced air heat & central AC. We have a couple of bedrooms upstairs that are colder than we like in the winter & too warm in the summer. We already run the blower constantly in the summer to get it cooler upstairs. Thinking about adding some inline duct fans to boost airflow to the problem rooms. The fans will be in the branch ducts in the basement since there is no access to the ducting anywhere closer. Distance from the fans to the room registers is 20-25ft. Will this help or am I wasting my time/money? Looking to boost/cut the temp by about 5 deg. Anyone have any experience with these?

Thanks.

-Dave

John Alvarez

I am forwarding this to my AC guy. I'll let you know what he says.

DaveHo

Thanks I appreciate it. I realized after I posted that there are several different styles available. For reference, these are what I am considering. Duct Fan

The thing I am most concerned about is the distance from the fan to the room registers. I read somewhere that the recommended distance is 10 ft or less. Since I am so far away I was going to up size to the 8" fan with my 6" ducts in hopes of being able to overcome the sizeable distance.

-Dave

Philip_G

I would pay someone to come in and do an airflow analysis, sounds like poorly designed/installed ducting. You might be able to balance the system by putting in dampers and adjusting the airflow to all the registers, but that's a bandaid, just like those fans are. Is it metal or flex duct? You might have some connections working loose if they're just held together by duct tape.

Also, an 8" fan isn't going to pull any more air through a 6" pipe than a 6" fan would. It's like running water through a pipe with a 2" restriction, the whole pipe might as well be 2"

anyway, honeywell has a nice computerized system that measures the airflow, takes the room measurements in, and does a quick calc to tell you what you should have. Shouldn't cost more than a couple hundred bucks to have it done on the whole house. Are you still under warranty? that report is handy to use against the contractor that installed the system.

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Elinor

Did you try adjusting the lever near the central fan? It's on the main duct coming off the fan unit.

I was amazed how much difference even a small adjustment made in my second floor heating/cooling. I haven't quite got it perfect, but it's much better than the position the builder left it in.

DaveHo

This house was built late 80's. There is no airflow control other than the room registers. Main trunk is fiber duct and the branches are flex, which I know stinks. The whole install is sloppy, and I know this. At some point before i finish off the basement and enclose the duct work, it will be redone right. For now, I am just looking for a quick fix. The rooms in question get blasted by the afternoon & evening sun in the summer and one of them gets almost no sun in the winter, so it's not really possible, with what I currently have, to balance things out using the registers alone. Also, we like to keep our pets out of the bedrooms, so the doors are always shut.

-Dave

Philip_G

How is the flex run? is it strung tight and straight or is it just looped along? Nothing wrong with flex if it's sized correctly and installed right.
You could look at installing a return into those two rooms, with the door shut as soon as the pressure equalizes, you get almost no airflow at all.

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